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Iron sulphate roasting for extraction of lithium from lepidolite
Iron sulphate roasting for extraction of lithium from lepidolite Van Tri Luong, Dong Jun Kang, Jeon Woong An, Duy Anh Dao, Myong Jun Kim, Tam Tran PII: DOI: Reference:
S0304-386X(13)00203-X doi: 10.1016/j.hydromet.2013.09.016 HYDROM 3780
To appear in:
Hydrometallurgy
Received date: Revised date: Accepted date:
10 April 2013 7 September 2013 29 September 2013
Please cite this article as: Luong, Van Tri, Kang, Dong Jun, An, Jeon Woong, Dao, Duy Anh, Kim, Myong Jun, Tran, Tam, Iron sulphate roasting for extraction of lithium from lepidolite, Hydrometallurgy (2013), doi: 10.1016/j.hydromet.2013.09.016
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ACCEPTED MANUSCRIPT IRON SULPHATE ROASTING FOR EXTRACTION OF LITHIUM FROM LEPIDOLITE
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By
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Van Tri Luong1, Dong Jun Kang2, Jeon Woong An2, Duy Anh Dao3,
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Myong Jun Kim1 and Tam Tran1
(1) Department of Energy & Resources Engineering, Chonnam National University, Gwangju, Republic of Korea
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(2) Technology Research Institute, Korea Resources Corp., Seoul, Republic of Korea (3) National Institute of Mining - Metallurgy Science and Technology, Hanoi, Vietnam
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Correspondence author: Tam Tran, [email protected]
Abstract
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Iron sulphate roasting and water leaching were investigated to extract lithium from lepidolite
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in this study. HSC modelling was used to simulate the process of roasting lepidolite with FeSO4.7H2O and CaO. Based on HSC, three-dimensional models were derived to predict the
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effect of temperature, SO4/Li and Ca/F molar ratios on the production of S- and F-containing gases (SO2, SO3, HF) and Li species (Li2SO4, LiKSO4) during roasting. It is believed that temperature and SO2/SO3 gases controlled the extraction of lithium from lepidolite during
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roasting while more soluble Li sulphate species determined the recovery of lithium during leaching. Using optimum parameters selected from HSC, roasting tests were conducted to produce calcines for leaching. Optimum roasting conditions were experimentally determined as 850 oC, 1.5 h, SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Roasting in a closed environment led to more Li extracted than with an open system. Leaching the calcines obtained from the open and closed systems with a water/calcine mass ratio of 1:1 at room temperature for 1 h yielded leach liquors containing ~7.9 g/L Li and ~8.7 g/L Li, corresponding to ~85% and ~93% extractions of Li from lepidolite, respectively . Keywords: lithium, lepidolite, roasting, leaching, iron sulphate, HSC modelling
ACCEPTED MANUSCRIPT HIGHLIGHTS Lithium was extracted from lepidolite during roasting with FeSO4.7H2O and CaO
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SO2, SO3 and HF gases were produced during roasting
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HSC modelling was used to simulate the roasting process
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About 93% lithium was extracted from roasting using a closed system
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Leach liquors containing maximum ~8.7 g/L Li were obtained from leaching
ACCEPTED MANUSCRIPT 1.
Introduction
Lithium plays an important role in many industries, especially in high-tech applications. Lithium has been used in the production of ceramics, glass, lubricating greases, electronics,
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medicine and rechargeable batteries, etc. The global lithium production has expanded from
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34,100 tonnes in 2011 to 37,000 tonnes in 2012 (USGS, 2013), representing an increase of
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nearly 10% within a year. The demand of lithium is predicted to increase steadily due to a high requirement in the manufacturing of electronic devices such as smartphones, laptop computers, power tools, etc. According to Roskill Information Services Ltd. (Roskill, 2009),
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an annual increase in lithium demand of 7% is projected from 2011 to 2025.
Sociedad de Quimica Minera de Chile SA (SQM), Rockwood Lithium in Chile, FMC Corp in
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Argentina, and Galaxy Resources Ltd. in Australia are known as the biggest manufacturers of lithium around the world. Of these, the companies from South America have produced lithium carbonate from salar brines, which are abundant in this region. Containing 0.06-0.15%
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Li, salar brines are considered as the more common raw materials for the lithium production.
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Other mineral resources have also been recently developed or evaluated to extract lithium such as spodumene (by Galaxy Resources Ltd. WA, Australia), china clay (by Goonvean Ltd.,
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Cornwall, UK) (Siame and Pascoe, 2011) and zinnwaldite wastes from tin-tungsten mines in Cinovec, the Czech Republic (Jandová et al., 2010), etc. Compared to brines, processing of lithium minerals is technically more difficult as extra operations are required, including
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beneficiation to produce a concentrate containing 1-3% Li and roasting in sulphate or carbonate to extract Li into water-soluble species before lithium can be solubilised into solutions. Conditions and results of major published studies on lithium recovery from ores are listed in Table 1.
During the treatment of lithium bearing minerals, ore concentrates of spodumene, lepidolite or zinnwaldite were first mixed with additives containing sodium sulphate (Kondás and Jandová, 2006; Jandová et al., 2009; Siame and Pascoe, 2011; Yan et al., 2012a, 2012b; Luong et al., 2013) or calcium carbonate (Jandová et al., 2010) before being roasted at high temperatures (850–1050 oC) in order to decompose such hard rocks and convert Li to soluble species such as Li2SO4, LiKSO4, Li2NaK(SO4)2, etc. Calcines produced were then leached in water at different solid to liquid ratios and temperatures from which stage Li was extracted. There was no discussion on the potential release of gases (such as SO2, HF, etc.) in the latest
ACCEPTED MANUSCRIPT studies, except from an early investigation by the US Bureau of Mines (Crocker et al., 1987).
Sulphation roasting has been applied in extracting Ni and Mo from lateritic ores (Guo et al.,
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2009; Wang and Wang, 2010) or Cu from sulphide minerals (Güntner and Hammerschmidt,
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2012). Galaxy Resources is using sulphuric acid to crack Li from its pre-roasted silicate host (spodumene) and produce Li2SO4 for leaching in its plant (Galaxy Resources Ltd., 2008,
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2010). The conversion of refractory or hard-to-leach metal oxides to sulphate is believed to be due to the reaction with SO3 gas as suggested by Li et al. (2010, 2011). In their studies, SO3 produced from the decomposition of K2S2O8 reacts with metals existing in sodium
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aluminosilicate (albite) and calcium aluminosilicate (anorthite) minerals, etc. and converts
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them to soluble metal sulphates.
Recent literature studies used sodium sulphate to extract Li from its silicate hosts. However at >950oC, a glass phase was formed making it difficult to recover calcines for leaching (Luong
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et al., 2013). The high sodium content in leach liquors would also create difficulty during
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lithium recovery using ion exchange for the production of high purity lithium products. Various calcium salts were used to control the release of fluoride into the leach liquors (Table
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1), without reference to its presence in the gaseous phase during roasting.
Thus, the aim of this study was to use iron sulphate (with/without CaO addition) as the additive mixed with lepidolite to extract lithium during roasting. The formation of gases (SO 2,
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SO3) during the decomposition of FeSO4.7H2O was studied as one of the key issues for extracting lithium from the concentrate to form soluble species. The role of CaO in reducing the release of F into gaseous or soluble forms was also investigated in this study. Thermodynamic modelling based on the HSC program (Outotec, 2011) was conducted to predict different reactions encountered during roasting and identify the effect of temperature, SO4/Li and Ca/F molar ratios on Li recovery. Leaching parameters including water/calcine mass ratio, leaching duration and temperature were also tested.
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Experimental
2.1.
Materials
ACCEPTED MANUSCRIPT A lepidolite ore (0.7% Li) collected from the BOAM mine (Gyeongsangbuk-do, Korea) was used as the material for this study. In most processes producing lithium from ores, beneficiation is required to upgrade the Li content to a concentration of ~1-3% Li before
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being intensively treated. Handpicking of the lepidolite grains (purple in colour) was
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therefore undertaken to yield a concentrate containing 1.79% Li before subjecting it to roasting tests. Its chemical composition is presented in Table 2 in which the content of Li was
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determined by ICP-AES after digestion of the concentrate whereas the other metal components were measured by X-Ray Fluorescence (XRF) analysis.
Equipment and chemicals
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2.2.
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XRF analysis (using Rigaku ZSX Primus II) was used to determine the chemical compositions of the concentrate, calcines and residues after leaching whereas their structures were determined by X-Ray Diffraction (XRD) analysis (Cu-tube60kv 50Ma, Phillips). Cation
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concentrations of leach liquors were measured by ICP-MS (Agilent A5500) whereas anions
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(SO4, F) were analysed using Ion Chromatography (ICS-2000, Dionex). A muffle furnace was used for batch-roasting. Heating mantles and hot plates were used for leaching
Experimental techniques
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2.3.
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experiments. All chemicals used in the study were of analytical grade.
In this study, lithium was extracted from lepidolite via roasting and then recovered by water leaching. During roasting, the concentrate was mixed with iron sulphate and calcium oxide at different molar ratios of SO4/Li (1:1 to 3.5:1) and Ca/F (0.5:1 to 2:1). They were thoroughly mixed before being poured into ceramic crucibles and then placed into the preheated muffle furnace for roasting. Two types of roasting were carried out including a closed system in which the crucibles were slightly covered by caps to ensure the gases liberated from the decomposition of FeSO4.7H2O do not quickly escape into the furnace atmosphere. The other was an open system in which there was no cap used. Various durations from 0.5 to 2 hours were selected for roasting. A temperature range of 800–950 oC was set for the tests. After roasting, the calcines were cooled to laboratory temperature (20-22 oC) before being manually ground. Finely ground samples were then subjected to water leaching to determine the leachability of Li species.
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Leaching was conducted at various temperatures ranging from 20 oC to 85 oC for 1 h. Magnetic bar stirrers were used for tests carried out at laboratory temperature whereas
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heating mantles with motored stirrers were used for high temperature leaching. A correctly
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weighed calcine sample (10-30 g) was introduced into a known amount of water (30-100 g) at liquid to solid mass ratios varying from 1:1 to 10:1. Preliminary tests showed that a steady
Results and discussion
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3.
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state was reached after 15 minutes. All leaching experiments were conducted in duplicate.
To investigate the effect of SO2/SO3 gases generated from the decomposition of iron sulphate,
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which were believed to play an important role in the extraction of lithium from lepidolite, two types of roasting system were applied as previously mentioned. A comparison of results obtained from roasting tests using both systems was carried out and discussed. In practice
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roasting is commonly conducted in an open system which is easier and more convenient.
Thermodynamic modeling using HSC
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3.1.
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Most of the results reported herewith therefore represented an open roasting system.
HSC program (version 7.1) was used to simulate thermodynamic models for roasting of lepidolite, FeSO4.7H2O and CaO mixtures from which experimental conditions including
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temperature, SO4/Li and Ca/F molar ratios were selected for real tests. The models were set up at the total pressure of 1 bar. As seen in Fig. 1a, the breakdown of lepidolite forms HF while iron sulphate is decomposing to create SO2 and SO3 (in the presence of oxygen) at temperatures of 350-400 oC. The detailed masses and percentages of these gases and other species predicted by HSC are listed in Table 3. It is clearly shown that HSC predicts a total amount of the gases and water vapour that is very close to the loss on ignition (LOI) measured from real tests. According to HSC, the percentages of SO2, SO3 and HF are 16.05%, 9.06% and 1.96% of the total gases and water vapour predicted, respectively. Mass balance of roasting runs conducted at 850 oC based on measured feeds and calcines shows that 2.67 g S (53.8% of total S) and 0.489 g F (79.3% of total F) were present in the gas phase during roasting (Table 4). The high level of these released gases therefore implies that a gas treatment step is required during lepidolite and iron sulphate roasting.
ACCEPTED MANUSCRIPT On the other hand, HSC indicates that Li2SO4 and LiKSO4 are the main lithium compounds formed (total 98% of all Li) from the reaction of lepidolite with iron sulphate at temperatures <900 oC (Fig. 1b). The model shows that the amount of Li2SO4 slightly decreases with the
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steady increase of the LiKSO4 quantity as the temperature rises. Both of them then start
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decomposing at >900 oC while other lithium compounds such as LiAlSiO4, LiAlO2, LiFeO2 begin to form. It is predicted that the formation of these compounds could reduce the
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recovery of lithium during water leaching due to their potentially low solubilities. This was confirmed by the reduction of Li extraction during leaching of calcines yielded from roasting at 925 oC, which will be discussed in detail in the subsequent section. The presence of Li2SO4
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in the calcine was later verified by the XRD pattern as shown in Fig. 9. The easy dissolution
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of Li2SO4 in water was also confirmed by its absence in the residue obtained after leaching. It is indicated that iron sulphate plays a different role compared to sodium sulphate in the interaction with lepidolite during roasting. Na2SO4 seems to be thermally stable and its
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decomposition to form SO2/SO3 takes place at much higher temperatures (750–800 oC)
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compared to iron sulphate (350–400 oC) as seen in Figs. 1a, 1c and 1d. For sodium sulphate roasting, (SO2 + SO3)/Li molar ratio of ~0.014 is predicted by HSC at 1000 oC at equilibrium,
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which means that the amount of SO2/SO3 produced is not enough to react with lithium from lepidolite in a gas – solid interaction. In fact, the LOI measured in the previous study on sodium sulphate roasting (Luong et al., 2013) was negligible. SO2/SO3 therefore could not be the main reactant extracting Li from lepidolite during roasting using sodium sulphate. Iron
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sulphate meanwhile is decomposed at a lower temperature and (SO2 + SO3)/Li molar ratio of ~1.87 at equilibrium is predicted at 850 oC. It is believed that the gas – solid interaction hence could be the main reaction mechanism taking place during roasting of lepidolite and iron sulphate.
Based on HSC results, several three-dimensional models were derived to investigate the effect of temperature, SO4/Li and Ca/F molar ratios on the production of major species containing Li, S and F. As shown in Fig. 1a, the formation of HF, SO2 and SO3 during the roasting of lepidolite, FeSO4.7H2O and CaO is unavoidable. Input amounts of iron sulphate and calcium oxide for HSC were therefore changed in order to determine optimal conditions at which the production of HF is minimised and the formation of SO2/SO3 is reasonable. As seen in Fig. 2a, high SO4/Li molar ratios used would create more S in gases as the result
ACCEPTED MANUSCRIPT of FeSO4.7H2O decomposition. An increase of Ca/F molar ratio could reduce the production of S gases possibly due to the preferential formation of CaSO4, which is clearly shown at 800 o
C. At a Ca/F molar ratio of <2:1, the release of HF is at the highest level at this temperature
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(Fig. 2b). The preferential formation of CaF2 could be the reason for the decrease of HF at
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higher Ca/F molar ratios. However, at higher temperatures (900 and 1000 oC) HSC predicts that more SO2, SO3 and HF are produced. The decomposition of CaSO4 and transformation of
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CaF2 at such temperatures are the reasons for the higher release of the gases from the roasting (Fig. 1a). In addition, the conversion of Li2SO4 and LiKSO4 to other Li species including
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LiFeO2, LiAlSiO4, etc. at high temperatures is also observed (Fig. 1b). Yielded amounts of Li2SO4 and LiKSO4 predicted by HSC are also shown in the 3D models
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(Fig. 3). As seen in Fig. 3a, roasting temperature has a significant influence on the formation of Li2SO4. An increase of temperature from 800 oC to 1000 oC at all SO4/Li molar ratios reduces its production. This could be explained by the transformation of Li2SO4 to other
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lithium compounds as mentioned previously. At low temperatures and Ca/F molar ratios of
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0.5:1 and 1:1, the creation of Li2SO4 seems to be independent on the increase of SO4/Li molar ratio. Only at 2:1 ratio of Ca/F, low ratios of SO4/Li would not produce the maximum amount
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of Li2SO4, which might be due to the preferential formation of CaSO4, thus reducing the quantity of SO2/SO3 required for Li extraction during roasting. The dependence of LiKSO4 on temperature is slightly different from that of Li2SO4 (Fig. 3b). It is shown that LiKSO4 increases in the range of 800–900 oC then starts decreasing at >950 oC. The change of SO4/Li
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molar ratios from 1:1 to 3.5:1 also does not seem to significantly affect the formation of LiKSO4 at low temperatures. Roasting temperature thus is the more important factor compared to Ca/F ratio in controlling the formation of Li2SO4 and LiKSO4 as well as the subsequent recovery of Li during leaching as a result.
HSC and three-dimensional models therefore provided an overview on the effect of temperature, SO4/Li and Ca/F molar ratios on the production of S-, F-containing gases and Li species. There is an indication that roasting at temperatures of >900 oC would enhance the formation of the gases (thus favouring the extraction of Li during roasting) but also reduce amounts of Li2SO4 and LiKSO4 created (due to the conversion to less soluble Li species) especially at low SO4/Li ratios (Fig. 3a). The increasing addition of CaO represented by the increase of Ca/F molar ratios plays an important role in decreasing both S and F gases. High Ca/F molar ratios however might cause a drop in the extraction of Li as less SO2/SO3 is
ACCEPTED MANUSCRIPT formed due to the preferential formation of CaSO4 instead. Hence, the optimum addition of CaO to mixtures of lepidolite and FeSO4.7H2O for roasting should be considered carefully.
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From HSC modelling the optimum conditions for each parameter were selected for Temperature of 800–900 oC to maximise the extraction of Li2SO4 and LiKSO4 and lower the release of SO2, SO3 and HF, -
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-
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conducting roasting experiments as follows:
SO4/Li molar ratio of > 2.5:1 to produce enough SO2/SO3 for the reaction with Li and formation of Li2SO4 and LiKSO4 during roasting,
Ca/F molar ratio of > 2:1 to minimise HF. However a Ca/F molar ratio of >1:1,
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especially at lower temperature (800 oC), would reduce the amounts of SO2/SO3 gases
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produced.
These conditions are almost conflicting with each other so a well balance set of conditions
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(temperature, SO4/Li and Ca/F molar ratios) has to be chosen to maximise the Li recovery. It
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seems that it is unavoidable not to liberate SO2/SO3 and HF under conditions for the maxium Li extraction (predicted to be 98%) in the form of soluble Li2SO4 and sparingly soluble
3.2.
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LiKSO4.
Roasting tests
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3.2.1. Reaction mechanism and effect of SO4/Li molar ratio The amount of SO2/SO3 formed from FeSO4.7H2O roasting with lepidolite is one of the key factors controlling the extraction of lithium from lepidolite. It is believed that the gas will react with lepidolite to extract lithium as Li2SO4 and LiKSO4. The main reactions taking place during the roasting process as derived from HSC were predicted as follows:
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FeSO4.7H2O FeSO4 + 7H2O
(Eq. 1)
12FeSO4 + 3O2 4Fe2(SO4)3 + 2Fe2O3
(Eq. 2)
Fe2(SO4)3 Fe2O3 + 3SO3
(Eq. 3)
KLi2AlSi4O10F(OH) + SO3 Li2SO4 + LiKSO4 + LiAlSiO4 + LiAlO2 + HF (Eq. 4)* (*) Main products can be found from HSC prediction (Figs 1a&b). The reaction is shown in the unbalanced form.
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There is an indication that the total pressure of the roasting system had an influence on the Li extraction. As seen in Fig. 4, HSC predicts that a reduction of the total pressure could lower
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the lithium recoverability from lepidolite. The amounts of Li2SO4 and LiKSO4 formed will be
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reduced when the total pressure drops below 0.5 bar, leading to a decrease of the total Li recovery from ~98% to ~60%. Such a low total pressure implies that lower partial pressures
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of SO2/SO3 in a close-to-vacuum or open system would reduce the Li recovery. In fact, only ~85% Li was extracted during tests conducted in an open environment. In contrast, roasting in a closed system (represented by total pressure > 1bar) by covering the crucibles could
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minimise the loss of SO2/SO3 to the furnace atmosphere, leading to a much higher Li
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extraction (~93%) as shown in Fig. 5.
An increase of SO4/Li molar ratios would enhance the extraction of lithium from lepidolite in which ~85% Li recovery was achieved at the ratio of 3:1 within 0.5 h roasting in an open
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environment (Fig. 5). SO4/Li molar ratios < 3:1 were found to be insufficient for completely
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extracting lithium from lepidolite. Higher ratios (> 3:1) however could not extract more lithium but would create more wasted S gases as predicted by HSC. The poor matching
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between the HSC prediction (at 1 bar) and real experimental results obtained from the open roasting at low SO4/Li molar ratios (Fig. 5) could be due to slow reaction kinetics and escaping SO2/SO3 as previously mentioned. However, the gap is narrowed when a closed system roasting was used. A lithium recovery of ~93% was achieved from closed system
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tests conducted for 1.5 h. The role of roasting time in increasing the extraction of lithium is subsequently reported.
As suggested by Li et al. (2010 and 2011) the extraction of metal ions such as Na, Ca, etc. from aluminosilicates (albite, anorthite) as metal sulphates is via the reaction with SO2/SO3 produced from the decomposition of potassium peroxodisulphate (K2S2O8). These gases are also created from the breakdown of iron sulphate at 350 – 400 oC during roasting with lepidolite in this study. As confirmed by HSC modelling, such a reaction mechanism is therefore believed to play the main role in the extraction of Li from the lepidolite.
3.2.2. Effect of roasting time
It was evident that roasting time did not much affect the extraction of lithium from lepidolite
ACCEPTED MANUSCRIPT when the open system was used (Fig. 6). Roasting for long time seemed to be unnecessary if the gases quickly escaped. Meanwhile, there is a dependence of the lithium extraction on roasting time when the closed system was applied. Increasing time from 0.5 h to 1.5 h sharply
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enhanced the recovery of lithium with the highest of ~93% Li achieved at the longer duration.
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3.2.3. Effect of roasting temperature
According to HSC, roasting at high temperatures >900 oC could reduce amounts of Li2SO4 and LiKSO4 produced due to their decomposition. The transformation of such lithium soluble
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compounds to other insoluble species including LiFeO2, LiAlSiO4 and LiAlO2 is predicted by HSC as shown in Fig. 1b. Li2SO4 and LiKSO4 play the main role in the complete release of
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Li during water leaching. Their lower formation during roasting at >950 oC would certainly lead to the decrease in the overall recovery of Li. As shown in Fig. 7, roasting at <850 oC could not result in a high extraction of lithium whereas >900 oC roasting also decreases Li
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recovery. The range of 850 – 900 oC is the best for Li extraction, which fits well with the
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prediction from HSC.
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3.2.4. Effect of Ca/F molar ratio
The addition of CaO into mixtures of lepidolite and iron sulphate during roasting aims to decrease the formation of HF escaped into the atmosphere and/or soluble F salts which causes
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high levels of F in leach liquors by forming insoluble CaF2. HSC predicts that high molar ratios of Ca/F are required to hinder the liberation of HF if high SO4/Li molar ratios are used as seen in Fig. 2b. To achieve high extractions of Li in real tests, SO4/Li molar ratios of ≥ 3:1 are required. Using large additions of CaO is therefore necessary in this case. The effect of Ca/F molar ratio on the Li extraction is illustrated in Fig. 8.
Mass balance for F amounts contained in lepidolite and calcines based on XRF analysis was used to identify the effect of CaO quantity added on the liberation of F in the form of gases (possibly mainly HF) during roasting. There is indication that when no CaO was used, most of F (~96%) contained in lepidolite was liberated in the gaseous form. The creation of Fcontaining gases in real tests was quickly reduced by the increase of CaO used as the Ca/F molar ratio was increased from 0:1 to 2:1 (Fig. 8). The important role of CaO in capturing F is therefore undeniable. However, an increase of Ca/F molar ratio >1:1 unfortunately would
ACCEPTED MANUSCRIPT lead to the decrease of Li extracted. This might be due to the preferential formation of CaSO4 from CaO, which could lessen the production of SO2/SO3 for the extraction of Li from lepidolite, as indicated in the three-dimensional models (Fig. 2a). Hence, the Ca/F ratio of 1:1
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was chosen to optimally recover Li as well as liberating an acceptable amount of F.
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Nevertheless, a system used to adsorb the F gases should be designed in practice (for example, using Ca(OH)2, CaCl2, etc.) to prevent their liberation into the atmosphere. Leaching the
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calcines obtained from roasting using the Ca/F ratio of 1:1 yielded leach liquors containing ~1% F while ~79% F was liberated as gases (Table 4, 5). The remaining amount of F might
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be contained in CaF2 as confirmed in the XRD pattern of Fig. 9.
XRD patterns of the calcine and the residue after leaching (Fig. 9) show that they mainly
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contain Fe2O3 and other major insoluble compounds including CaSiO3, CaSO4, CaF2, etc. Li2SO4 and Rb2SO4 are major soluble Li and Rb species existing in the calcine, which are completely dissolved during leaching. The presence of these compounds fits well with the
Leaching tests
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3.3.
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prediction of HSC as shown in Fig. 1b.
3.3.1. Effect of water/calcine mass ratio
Leaching at different water/calcine mass ratios from 1:1 to 10:1 yielded almost the same
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recovery of lithium as shown in Fig. 10, with low concentrations of Li obtained at high water/calcine mass ratios. Using Na2SO4 mixed with lepidolite in roasting, Luong et al. (2013) reported that there was a dependence of the Li extraction on water/calcine mass ratios used in leaching. The low solubility of LiKSO4 and LiF was the reason for the difficult dissolution of Li values from the calcines produced by sodium sulphate roasting. The insignificant amount of F contained in leach liquors in this study (Table 5) at 1:1 mass ratio of water/calcine would minimise the effect of LiF in limiting the dissolution of Li in this case. Concentrations of 0.15-0.19 g/L F, corresponding to 0.96-1.2% F recoveries as soluble species were obtained from calcines produced from iron sulphate roasting, whereas 1.14 g/L F, corresponding to 94.8% F recovery was yielded using sodium sulphate in the last study (Luong et al., 2013). In addition, the XRD pattern of the calcine obtained from lepidolite and iron sulphate roasting (Fig. 9) shows that Li2SO4 is the main existing soluble Li compound. Using calcines obtained from the open and closed system roasting and leaching at 1:1 mass ratio of water/calcine, a
ACCEPTED MANUSCRIPT maximum of ~85% and ~93% Li were recovered with high concentrations of ~7.9 g/L and ~8.7g/L Li, respectively. The results are very good when being compared to much lower Li concentrations obtained in most previous studies reported and listed in Table 1. This is
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considered an important improvement as a concentrated Li liquor produced from the process
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would be easily processed. In the case of Na2SO4 roasting, high amounts of H2O must be used to achieve high recoveries of Li, which are accompanied by low Li concentrations. A Li
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concentration stage is therefore necessary (such as evaporation, ion exchange, etc.) before Li2CO3 is produced. In practice, evaporation (more than 10-folds to achieve Li up to 3M Li for Li2CO3 precipitation) requires a high energy input whereas high contents of Na in leach
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liquors prevent the efficient concentration and recovery of Li by ion exchange resins. The lithium recoveries of ~85% and ~93% obtained from the open and closed roasting systems,
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respectively as well as the above advantages are the reasonable motivations to choose iron sulphate as a reactant instead of sodium sulphate.
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3.3.2. Effect of leaching temperature
Leaching temperature also controlled the release of Li when Na2SO4 was used as the
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sulphation agent (Luong et al., 2013). Calcines obtained from Na2SO4 and lepidolite roasting required high temperature (85 oC) for maximally extracting lithium. On the contrary, an independence of the Li extraction on leaching temperature for calcines obtained from iron sulphate roasting in the open system was observed, as documented in Fig. 11. An average of
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85% Li recovery was obtained at the laboratory temperature (~20oC) whereas leaching at higher temperatures also produced the same results. The absence of LiF and the low LiKSO4 contained in calcines could be the main reason for that difference.
3.3.3. Effect of leaching time
As shown in Fig.12, a steady state for the lithium extraction was quickly obtained after 15 minutes of leaching. Li2SO4, the main soluble lithium compound, seemed to be easily dissolved into water. The maximum extraction of lithium at ~85% was achieved during leaching at room temperature using the water/calcine mass ratio of 1:1 in which the calcine was obtained from the open roasting system.
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Conclusions
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4.
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HSC modelling and three-dimensional models built from its results outlined the effect of key factors including temperature, SO4/Li and Ca/F molar ratios on the extraction of lithium from
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lepidolite as well as the production of S- and F-containing gases during roasting. HSC predicted the best conditions for Li extraction during sulphation as 800-900 oC and SO4/Li molar ratios >2.5:1. A Ca/F molar ratio of >2:1 would minimise the generation of HF,
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although this would cause a lower formation of SO2/SO3 required for Li extraction, especially at a low SO4/Li molar ratio. Using optimum conditions predicted by HSC, roasting tests were
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carried out to produce calcines that were then leached to recover Li. A leach liquor containing a high concentration of ~8.7 g/L Li, corresponding to ~93% Li recovery was yielded from leaching of calcines roasted at 850 oC for 1.5 h in a closed system. Meanwhile, roasting in an
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open system for 0.5-2 h yielded ~83-85% Li recoveries and liquors containing ~7.7-7.9 g/L
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Li were produced. SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively were the best choices for the materials used in roasting. Such the results were obtained at the water/calcine
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mass ratio of 1:1 and room temperature leaching. Recovery of Li from lepidolite using iron sulphate is therefore better compared to sodium sulphate as a roasting additive.
Acknowledgement
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5.
This study was supported by a research grant from Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), Ministry of Knowledge Economy, Korea (No. 2010 T100100408).
ACCEPTED MANUSCRIPT REFERENCES Crocker, L., Lien, R.H. and Others, 1987. Lithium and its recovery from low-grade Nevada clays, pub: US Bureau of Mines, Department of Interior, Bulletin 691. Accessed on 2 October
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2011, http://digicoll.manoa.hawaii.edu/techreports/PDF/USBM-691.pdf. Galaxy Resources Ltd., 2008, 2010. Accessed on 2 November 2011.
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http://www.galaxyresources.com.au/documents/GXY03LithiumCarbonateTestworkResults.p df
http://www.galaxyresources.com.au/project_jiangsu.shtml
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http://metalsplace.com/news/articles/33315/galaxy-resources-ups-lithium-ore-reserves-by-23/
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Guo, X.Y., Li, D., Park, K.H., Tian, Q.H., Wu, Z., 2009. Leaching behavior of metals from a limonitic Ni laterite using a sulphation roasting-leaching process. Hydrometallurgy, 99, 144150.
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Güntner, J., Hammerschmidt, J., 2012. Sulphating roasting of copper-cobalt concentrates. J. S.
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Afr. Inst. Min. Metall, 112, 455-460.
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HSC Chemistry software, Version 7.1, Outotec, 2011. Jandová, J., Vu, H.N., Belková, T., Dvořák, T., Kondás, J., 2009. Obtaining Li2CO3 from zinnwaldite wastes. Ceramics-Silikáty, 53(2), 108-112.
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Jandová, J., Dvořák, P., Vu, H.N., 2010. Processing of zinnwaldite waste to obtain lithium carbonate. Hydrometallurgy, 103, 12-18. Kondás, J., Jandová, J., 2006. Lithium extraction from zinnwaldite wastes after gravity dressing of Sn-W ores. Acta Metallurgica Slovaca, 12, 197-202. Li, E.Y., Chareev, D.A., Shilobreeva, S.N., Grichuk, D.V., Tyutyunnik, O.A., 2010. Experimental study of sulphur dioxide interaction with silicates and aluminosilicates at temperatures of 650 and 850 oC. Geochemistry International, 48, 10, 1039 – 1046. Li, E.Y., Grichuk, D.V., Shilobreeva, S.N., Chareev, D.A., 2011. Interaction between (alumino) silicates and SO2 – containing gas: experiment and thermodynamic model. Vestnik Otdelenia nauk o Zemle RAN, 3, NZ6064, doi:10.2205/2011NZ000194. Luong, V.T., Kang, D.J., An, J.W., Kim, M.J., Tran, T., 2013. Factors affecting the extraction
ACCEPTED MANUSCRIPT of lithium from lepidolite. Hydrometallurgy, 134-135, 54-61. Siame, E., Pascoe, D., 2011. Extraction of lithium from micaceous waste from china clay
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production. Minerals Engineering, 24, 1595-1602.
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Sitando, O., Crouse, P.L., 2012. Processing of a Zimbabwean petalite to obtain lithium
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carbonate. International Journal of Mineral Processing, 102-103, 45-50. Roskill Information Services Ltd, The Economics of Lithium, 2009. pub: United Kingdom, 01 February 2009, Eleventh Edition, ISBN 0862145554.
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Yan, Q., Li, X., Wang, Z., Wu, X., Guo, H., Hu, Q., Peng, W., 2012a. Extraction of lithium from lepidolite by sulphation roasting and water leaching. Journal of Int. Mineral Processing,
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110-111, 1-5.
Yan, Q., Li, X., Wang, Z., Wu, X., Guo, H., Hu, Q., Peng, W., Wang, J., 2012b. Extraction of
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valuable metals from lepidolite. Hydrometallury, 117-118, 116-118.
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USGS - US Geological Survey, 2013. Mineral Commodity Summaries – Lithium, pub: USGS, Virginia, January 2013. 94-95, ISBN 978–1–4113–3548–6.
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Wang, M.Y., Wang, X.W., 2010. Extraction of Mo and Ni from carbonaceous shale by
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oxidative roasting, sulphation roasting and water leaching. Hydrometallurgy, 102, 50-54.
ACCEPTED MANUSCRIPT List of Tables Table 1. Experimental profiles and results of several published studies on processing of Li
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from mineral sources.
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Table 2. Composition (%) of the lepidolite concentrate by XRF and ICP – AES.
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Table 3. Loss on ignition (LOI) obtained from three real tests and produced gases predicted by HSC. Used materials: lepidolite concentrate: 20 g, FeSO4.7H2O: 43.02 g, CaO: 1.82 g and roasting temperature of 850 oC.
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Table 4. Mass balance for roasting at 850 oC (analysis of S and F by XRF). Table 5. Typical major components and concentrations (g/L) of leach liquors and extractions
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(%) from tests using water/calcine mass ratio of 1:1 at room temperature. Calcine from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively in different roasting
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systems.
ACCEPTED MANUSCRIPT Table 1: Experimental profiles and results of several published studies on processing of Li
Mineral tested Li % K% F% Best roast temp, oC Roasting time, h
Lepidolite 2.55 9.31 3.69
Siame & Pascoe, (2011) Zinnwaldite 0.96 7.94 3.36
1000
850
850
880
950
825
1
0.5
0.5
1
1
Additives
Na2SO4
Na2SO4
Na2SO4,K2SO4, CaO
Na2SO4, CaCl2
CaSO4, Ca(OH)2
CaCO3
H2SO4 (300oC, 2nd stage)
85
85
ambient
ambient
90
90-95
50
0.5
0.5
0.5
0.5
0.5
2-18:1
10:1
2.5:1
0.8:1
10:1
5:1
7.5:1
~90
>90
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from mineral sources.
~90
96
~90
97.3
1-3
Expected to be ~1
4.39
8.53
0.69
0.4
5.7
Jandová et al, (2010)
Sitando & Crouse (2012)
Lepidolite 2.00 6.50 4.46
Lepidolite 2.00 6.50 4.46
Zinnwaldite 1.4 6.62 unreported
Zinnwaldite 1.21 10.97 unreported
Petalite/lepidolite 1.9 0.37 0.01 1100 (1st stage)
~90
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Jandová et al, (2009)
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3
Yan et al, (2012b)
2
1
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Best leach temp, oC Leaching time, h Water/calcine ratio Max. Li Extract., % Liquor Li concentration, g/L
0.5
Yan et al, (2012a)
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Luong et al, 2013
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Table 2. Composition (%) of the lepidolite concentrate by XRF and ICP – AES SiO2 Al2O3 Fe2O3 P2O5 Na2O K2O MgO CaO MnO Rb2O Cs2O Li 57.7 22.9 0.17 0.34 0.80 9.15 0.47 1.91 0.13 0.81 0.25 1.79
F 3.08
ACCEPTED MANUSCRIPT Table 3. Loss on ignition (LOI) obtained from three real tests and produced gases predicted by HSC. Used materials: lepidolite concentrate: 20 g, FeSO4.7H2O: 43.02 g, CaO: 1.82 g and
Experiments LOI SO2 (gas)
4.25
SO3 (gas) H2O (gas) HF (gas) LiF (gas)
9.06
19.31
72.92
0.52
1.96
0.00034
0.0013
0.0000019 26.48
0.0000072 100
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Li2F2 (gas) Total
16.05
2.40
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HSC
Percentage (%)
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26.6 ± 0.3
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Mass (g)
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roasting temperature of 850 oC.
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Table 4. Mass balance for roasting at 850 oC (Analysis of S and F by XRF) Component
Mass (g)
S (g)
F (g)
20.00
0
0.617
FeSO4.7H2O
43.02
4.96
0
CaO
1.82
0
0
64.84
4.96
0.617
HSC
26.48
3.09
0.494
Experiment
26.25
2.67* (53.8%) 2.29
0.489* (79.3%) 0.128
Roasting
Feed
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Lepidolite concentrate
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Total
Gases (SO2, HF, SO3, etc) + H2O (vap)
Product Calcine Total (Exp. Gases+Calcines)
38.59 64.84
* Calculated from: Total (S or F in Feed) – S or F in Calcine
ACCEPTED MANUSCRIPT
Table 5. Typical major components and concentrations (g/L) of leach liquors and extractions (%) from tests using water/calcine mass ratio of 1:1 at room temperature. Calcine from roasts
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at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively in different roasting
1.0
17.6
0.03
0.15
0.21
82.2
0.19
21.6
32.3
44.1
0.07
10.1
38.1
29.3
1.2
7.9
1.1
0.2
85.4
28.6
17.3
8.7
1.3
93.3
33.2
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0.3
Cs
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Closed system, 1.5 h
0.14
Rb
Na
K
Ca
Mg
Mn
SO4
F
0.8
13.4
0.03
0.20
70.4
0.15
27.1
34.2
0.07
9.59
36.5
25.4
0.96
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Open system, 0.5 h
Concentration (g/L) Extraction (%) Concentration (g/L) Extraction (%)
Li
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Roasting condition
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systems.
ACCEPTED MANUSCRIPT List of Figures Fig. 1. HSC models for (a) and (b): roasting mixture of lepidolite concentrate (20 g), FeSO4.7H2O (43.02 g) and CaO (1.82 g), corresponding to SO4/Li and Ca/F molar ratios of
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3:1 and 1:1, respectively; (c) and (d): roasting mixture of lepidolite and Na2SO4 from Luong
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et al. (2013), therein “dot curves” represent for Na2SO4 roasting only (without lepidolite).
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Equilibrium pressure was set at 1 bar.
Fig. 2. Three-dimensional models showing the relationship of SO4/Li and Ca/F molar ratios with amounts of S and F contained in escaped gases during roasting of 20 g lepidolite (0.026
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mol), FeSO4.7H2O (0.026-0.156 mol, corresponding to 0.5-3:1 SO4/Li molar ratio) and CaO (0.016-0.224 mol, corresponding to 0.5-7:1 Ca/F molar ratio) at different temperatures.
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Fig. 3. Three-dimensional models showing the relationship of temperature, SO4/Li molar ratio and recoverable mass of two major Li species (Li2SO4 and LiKSO4) at different Ca/F
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molar ratios. Conditions as in Fig. 2.
Fig. 4. Effect of total pressure on lithium recoverability based on HSC prediction. Simulation
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using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC.
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Fig. 5. Effect of SO4/Li molar ratio on Li extraction. (a) and (b) this study - calcines from roasts using Ca/F molar ratio of 1:1 at 850 oC in open and closed system, respectively; (c) this study – HSC prediction at 850 oC and 1 bar pressure; (d) and (e) - real results and HSC
pressure.
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prediction for sodium sulphate roasting from Luong et al. (2013) at 1000 oC and 1 bar
Fig. 6. Effect of roasting time on Li extraction. Calcines from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1. Fig. 7. Effect of roasting temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1 in open system, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1. Fig. 8. Effect of Ca/F molar ratio on Li extraction and F liberation during roasting. Calcines from roasts using SO4/Li molar ratio of 3:1 at 850 oC for 0.5 h in open system and leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
ACCEPTED MANUSCRIPT Fig. 9. XRD patterns of (a) lepidolite concentrate, (b) calcine and (c) residue from roast of lepidolite, FeSO4.7H2O and CaO for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching at room temperature for 1 h using
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water/calcine mass ratio of 1:1.
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Fig. 10. Effect of water/calcine mass ratio on Li extraction and concentration. Calcines from
open system. Leaching at room temperature for 1 h.
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roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in
Fig. 11. Effect of leaching temperature on Li extraction. Calcines from roasts for 0.5 h using
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SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching for 1 h using water/calcine mass ratio of 10:1.
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Fig. 12. Effect of leaching time on Li extraction and concentration. Calcine from roast for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system.
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Leaching at room temperature using water/calcine mass ratio of 1:1.
ACCEPTED MANUSCRIPT File: C:\HSC7\Gibbs\new period\chose\Lepi_FeSO4.OGI
kmol 4E-05 0.04
SO2 (g)
9E-05
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Fe2(SO4)3
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SO2(g)
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Fe2O3 Fe2O3(G)
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LiAlSiO4 LiFeO2
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0E+00 0.000
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SO2(g) (g) SO2 0E+00 0.000
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400
600
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600 600
Temperature ( (ooC) Temperature C)
Temperature C) Temperature (ooC)
(c) (c)
(d) (d)
800
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Fig. 1. HSC models for (a) and (b): roasting mixture of lepidolite concentrate (20 g), FeSO4.7H2O (43.02 g) and CaO (1.82 g), corresponding to SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively; (c) and (d): roasting mixture of lepidolite and Na2SO4 from Luong et al. (2013), therein “dot curves” represent for Na2SO4 roasting only (without lepidolite). Equilibrium pressure was set at 1 bar.
FeSO4
5E-06
8E-06 0.008
0.2 600
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FeSO4
6E-06 0.006
Na2SO4
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0
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0.3
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0.0003 0.3
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0.6
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mol
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mol kmol
Na Na2SO4 (R) 2SO4 (R)
0.0005 0.5
0
Fe2(SO4)3
LiKSO4
LiAlO2
Na2SO4(R)
Na 2SO4 Na2SO4
0.6
0.2
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200
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Na2SO4 Na2SO4
0.0006 0.6
0.0002 0.2
0E+00 0.00
Li2SO4
LiKSO4
8E-06 0.008
Na Na2SO4 (R) 2SO4 (R) 0.7
0.4
5E-06
File: C:\HSC7\Gibbs\CNU\HSC for paper\lepi (F)_Na2SO4_CNU-roast 15b.OGI
0.0007 0.7
0.0004 0.4
1E-05 0.01
4E-06 0.004
600 400
1000
2E-05
5E-06
600 600
(b) (a)
800
2E-05 0.02
6E-06 0.006
600
400
CaSiO3
Temperature 1000 C
800
400 400
mol
600
Temperature (oC)
Na2SO4
Na2SO4
200
mol kmol
0.8
0.0008 0.8
400
CaSiO3
Li2SO4
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200
3E-05
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0E+00 0.00 0 0
CaSO4
800
1E-05
800 800
CaSO4
HF(g)
(c) (c)
2E-05 0.02
HF (g)
Temperature ( (ooC) Temperature C)
3E-05
Fe2O3
3E-05 0.03
mol
Temperature C
Na2SO4 (R)
4E-05 0.04
SO3(g)
1000
5E-05
SO3 (g)
1000 1000
6E-05 0.06
Na2SO4
Na2SO4(R)
7E-05
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8E-05 0.08
Na2SO4 (R)
mol
File: C:\HSC7\Gibbs\CNU\HSC for paper\lepi (F)_Na2SO4_CNU-roast 15b.OGI
4E-05
(d) (d)
kmol
1E-04 0.10
1000
Temperatu C
1000 1000
ACCEPTED MANUSCRIPT 1000oC
1000oC 0.50
2.0
0.25
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1.5
900oC
4.0 2.0
2.5 1.5
0.0
0.5 0.5
2.0 3.5 o Ca/F molar ratio 800 C
5.0
4.0 2.0
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2.5 1.5
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0.5 0.5
2.0 3.5 Ca/F molar ratio
5.0
(a)
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0.00
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800oC
0.00
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2.0 3.5 Ca/F molar ratio 900oC
S in gases (g)
0.5
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0.0
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0.50 0.25
2.5 1.5 0.5
0.00 0.5
2.0
3.5
5.0
6.5
Ca/F molar ratio
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(b)
Fig. 2. Three-dimensional models showing the relationship of SO4/Li and Ca/F molar ratios
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with amounts of S and F contained in escaped gases during roasting of 20 g lepidolite (0.026 mol), FeSO4.7H2O (0.026-0.156 mol, corresponding to 0.5-3:1 SO4/Li molar ratio) and CaO
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(0.016-0.224 mol, corresponding to 0.5-7:1 Ca/F molar ratio) at different temperatures.
F in gases (g)
2.5
4.0
ACCEPTED MANUSCRIPT Li2SO4
LiKSO4
Ca/F: 2:1
Ca/F: 2:1 0.30 1000 950 900 850 800
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0.20 0.10 1.0 1.5 2.0 2.5 3.0 3.5
1.5
0.10 2.0
2.5
3.0
3.5
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Ca/F: 1:1
0.13
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1000 950 900 850 800
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Ca/F: 1:1
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Ca/F: 0.5:1
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SO4/Li molar ratio (a)
0.16
1000 950 900 850 800
0.13 0.10
1.0
1.5
2.0
2.5
3.0
3.5
Ca/F: 0.5:1 0.16
1000 950 900 850 800
0.13 0.10 1.0
1.5
2.0
2.5
3.0
3.5
SO4/Li molar ratio (b)
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Fig. 3. Three-dimensional models showing the relationship of temperature, SO4/Li molar ratio and recoverable mass of two major Li species (Li2SO4 and LiKSO4) at different Ca/F
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molar ratios. Conditions as in Fig. 2.
Li mass (g)
0.20
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1000 950 900 850 800
Li mass (g)
0.30
ACCEPTED MANUSCRIPT 100
IP
T
60 40
SC R
Recoverable Li (%)
80
20
LiKSO4
Li2SO4
0 0.5
1.0
1.5
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0.0
Total Li
Total pressure (bar)
Fig. 4. Effect of total pressure on lithium recoverability based on HSC prediction. Simulation
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using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC.
100
(b)
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(c)
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(a)
(e)
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Extraction (%)
80
60
(d)
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Exp_iron sulphate_850C_1.5h Exp_iron sulphate_850C_0.5h Exp_sodium sulphate_1000C
20
HSC_iron sulphate_850C HSC_sodium sulphate_1000C
0
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1
2
3
4
SO4/Li molar ratio
Fig. 5. Effect of SO4/Li molar ratio on Li extraction. (a) and (b) this study - calcines from roasts using Ca/F molar ratio of 1:1 at 850 oC in open and closed system, respectively; (c) this study – HSC prediction at 850 oC and 1 bar pressure; (d) and (e) - real results and HSC prediction for sodium sulphate roasting from Luong et al. (2013) at 1000 oC and 1 bar pressure.
ACCEPTED MANUSCRIPT 100
T IP
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closed system
70
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Extraction (%)
90
open system 60 0.0
0.5
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Time (h)
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Fig. 6. Effect of roasting time on Li extraction. Calcines from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Leaching at room temperature for 1 h
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using water/calcine mass ratio of 1:1.
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100
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Extraction (%)
80 60
40 20 0
750
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Temperature
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Fig. 7. Effect of roasting temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1 in open system, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
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ACCEPTED MANUSCRIPT
Li Extraction
20
20
F Liberation 0 0.5
1.0
1.5
2.0
0
2.5
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0.0
Ca/F molar ratio
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Fig. 8. Effect of Ca/F molar ratio on Li extraction and F liberation during roasting. Calcines from roasts using SO4/Li molar ratio of 3:1 at 850 oC for 0.5 h in open system and leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
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CaSiO KLi2CaSiO Al1.128 3 3Si3.868O11FH CaSO CaSO 4 4
a)
CaFCaF 2 2 Li2SO Li24SO4
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Counts Counts
800 400 400 600 0 0 10
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Hematite Fe2Fe O32O3 Hematite Maghemite γ - Fe O32O3 Maghemite γ - 2Fe
30
50
b)
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Hematite Fe2O3 Fe2O3 Maghemite γ - Fe2O3 γ-Fe2O3
Rb 2Rb SO24SO4 CaSiO3 Hematite Fe2O3 CaSO4 Maghemite γ - Fe2O3 70 CaF 90 2 CaSiO3 Calcine Li 2SO4 CaSO4 Rb 2SO4 CaF2 Li2SO4 Rb 2SO4
200 c)
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70
90 Residue
200
0
10
30
50
70
90
0
10 1 10
30 3 30
50 5 2-Theta 2-Theta
70 7
9 90
Fig. 9. XRD patterns of (a) lepidolite concentrate, (b) calcine and (c) residue from roast of 10
30
50
70
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lepidolite, FeSO4.7H2O and CaO for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, 2-Theta respectively at 850 oC in open system. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
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Water/calcine mass ratio
Fig. 10. Effect of water/calcine mass ratio on Li extraction and concentration. Calcines from
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roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching at room temperature for 1 h.
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Fig. 11. Effect of leaching temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching for 1 h using water/calcine mass ratio of 10:1.
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Time (min)
Fig. 12. Effect of leaching time on Li extraction and concentration. Calcine from roast for 0.5
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h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system.
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Leaching at room temperature using water/calcine mass ratio of 1:1.
S0304-386X(13)00203-X doi: 10.1016/j.hydromet.2013.09.016 HYDROM 3780
To appear in:
Hydrometallurgy
Received date: Revised date: Accepted date:
10 April 2013 7 September 2013 29 September 2013
Please cite this article as: Luong, Van Tri, Kang, Dong Jun, An, Jeon Woong, Dao, Duy Anh, Kim, Myong Jun, Tran, Tam, Iron sulphate roasting for extraction of lithium from lepidolite, Hydrometallurgy (2013), doi: 10.1016/j.hydromet.2013.09.016
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ACCEPTED MANUSCRIPT IRON SULPHATE ROASTING FOR EXTRACTION OF LITHIUM FROM LEPIDOLITE
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By
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Van Tri Luong1, Dong Jun Kang2, Jeon Woong An2, Duy Anh Dao3,
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Myong Jun Kim1 and Tam Tran1
(1) Department of Energy & Resources Engineering, Chonnam National University, Gwangju, Republic of Korea
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(2) Technology Research Institute, Korea Resources Corp., Seoul, Republic of Korea (3) National Institute of Mining - Metallurgy Science and Technology, Hanoi, Vietnam
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Correspondence author: Tam Tran, [email protected]
Abstract
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Iron sulphate roasting and water leaching were investigated to extract lithium from lepidolite
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in this study. HSC modelling was used to simulate the process of roasting lepidolite with FeSO4.7H2O and CaO. Based on HSC, three-dimensional models were derived to predict the
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effect of temperature, SO4/Li and Ca/F molar ratios on the production of S- and F-containing gases (SO2, SO3, HF) and Li species (Li2SO4, LiKSO4) during roasting. It is believed that temperature and SO2/SO3 gases controlled the extraction of lithium from lepidolite during
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roasting while more soluble Li sulphate species determined the recovery of lithium during leaching. Using optimum parameters selected from HSC, roasting tests were conducted to produce calcines for leaching. Optimum roasting conditions were experimentally determined as 850 oC, 1.5 h, SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Roasting in a closed environment led to more Li extracted than with an open system. Leaching the calcines obtained from the open and closed systems with a water/calcine mass ratio of 1:1 at room temperature for 1 h yielded leach liquors containing ~7.9 g/L Li and ~8.7 g/L Li, corresponding to ~85% and ~93% extractions of Li from lepidolite, respectively . Keywords: lithium, lepidolite, roasting, leaching, iron sulphate, HSC modelling
ACCEPTED MANUSCRIPT HIGHLIGHTS Lithium was extracted from lepidolite during roasting with FeSO4.7H2O and CaO
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SO2, SO3 and HF gases were produced during roasting
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HSC modelling was used to simulate the roasting process
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About 93% lithium was extracted from roasting using a closed system
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Leach liquors containing maximum ~8.7 g/L Li were obtained from leaching
ACCEPTED MANUSCRIPT 1.
Introduction
Lithium plays an important role in many industries, especially in high-tech applications. Lithium has been used in the production of ceramics, glass, lubricating greases, electronics,
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medicine and rechargeable batteries, etc. The global lithium production has expanded from
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34,100 tonnes in 2011 to 37,000 tonnes in 2012 (USGS, 2013), representing an increase of
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nearly 10% within a year. The demand of lithium is predicted to increase steadily due to a high requirement in the manufacturing of electronic devices such as smartphones, laptop computers, power tools, etc. According to Roskill Information Services Ltd. (Roskill, 2009),
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an annual increase in lithium demand of 7% is projected from 2011 to 2025.
Sociedad de Quimica Minera de Chile SA (SQM), Rockwood Lithium in Chile, FMC Corp in
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Argentina, and Galaxy Resources Ltd. in Australia are known as the biggest manufacturers of lithium around the world. Of these, the companies from South America have produced lithium carbonate from salar brines, which are abundant in this region. Containing 0.06-0.15%
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Li, salar brines are considered as the more common raw materials for the lithium production.
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Other mineral resources have also been recently developed or evaluated to extract lithium such as spodumene (by Galaxy Resources Ltd. WA, Australia), china clay (by Goonvean Ltd.,
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Cornwall, UK) (Siame and Pascoe, 2011) and zinnwaldite wastes from tin-tungsten mines in Cinovec, the Czech Republic (Jandová et al., 2010), etc. Compared to brines, processing of lithium minerals is technically more difficult as extra operations are required, including
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beneficiation to produce a concentrate containing 1-3% Li and roasting in sulphate or carbonate to extract Li into water-soluble species before lithium can be solubilised into solutions. Conditions and results of major published studies on lithium recovery from ores are listed in Table 1.
During the treatment of lithium bearing minerals, ore concentrates of spodumene, lepidolite or zinnwaldite were first mixed with additives containing sodium sulphate (Kondás and Jandová, 2006; Jandová et al., 2009; Siame and Pascoe, 2011; Yan et al., 2012a, 2012b; Luong et al., 2013) or calcium carbonate (Jandová et al., 2010) before being roasted at high temperatures (850–1050 oC) in order to decompose such hard rocks and convert Li to soluble species such as Li2SO4, LiKSO4, Li2NaK(SO4)2, etc. Calcines produced were then leached in water at different solid to liquid ratios and temperatures from which stage Li was extracted. There was no discussion on the potential release of gases (such as SO2, HF, etc.) in the latest
ACCEPTED MANUSCRIPT studies, except from an early investigation by the US Bureau of Mines (Crocker et al., 1987).
Sulphation roasting has been applied in extracting Ni and Mo from lateritic ores (Guo et al.,
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2009; Wang and Wang, 2010) or Cu from sulphide minerals (Güntner and Hammerschmidt,
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2012). Galaxy Resources is using sulphuric acid to crack Li from its pre-roasted silicate host (spodumene) and produce Li2SO4 for leaching in its plant (Galaxy Resources Ltd., 2008,
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2010). The conversion of refractory or hard-to-leach metal oxides to sulphate is believed to be due to the reaction with SO3 gas as suggested by Li et al. (2010, 2011). In their studies, SO3 produced from the decomposition of K2S2O8 reacts with metals existing in sodium
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aluminosilicate (albite) and calcium aluminosilicate (anorthite) minerals, etc. and converts
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them to soluble metal sulphates.
Recent literature studies used sodium sulphate to extract Li from its silicate hosts. However at >950oC, a glass phase was formed making it difficult to recover calcines for leaching (Luong
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et al., 2013). The high sodium content in leach liquors would also create difficulty during
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lithium recovery using ion exchange for the production of high purity lithium products. Various calcium salts were used to control the release of fluoride into the leach liquors (Table
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1), without reference to its presence in the gaseous phase during roasting.
Thus, the aim of this study was to use iron sulphate (with/without CaO addition) as the additive mixed with lepidolite to extract lithium during roasting. The formation of gases (SO 2,
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SO3) during the decomposition of FeSO4.7H2O was studied as one of the key issues for extracting lithium from the concentrate to form soluble species. The role of CaO in reducing the release of F into gaseous or soluble forms was also investigated in this study. Thermodynamic modelling based on the HSC program (Outotec, 2011) was conducted to predict different reactions encountered during roasting and identify the effect of temperature, SO4/Li and Ca/F molar ratios on Li recovery. Leaching parameters including water/calcine mass ratio, leaching duration and temperature were also tested.
2.
Experimental
2.1.
Materials
ACCEPTED MANUSCRIPT A lepidolite ore (0.7% Li) collected from the BOAM mine (Gyeongsangbuk-do, Korea) was used as the material for this study. In most processes producing lithium from ores, beneficiation is required to upgrade the Li content to a concentration of ~1-3% Li before
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being intensively treated. Handpicking of the lepidolite grains (purple in colour) was
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therefore undertaken to yield a concentrate containing 1.79% Li before subjecting it to roasting tests. Its chemical composition is presented in Table 2 in which the content of Li was
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determined by ICP-AES after digestion of the concentrate whereas the other metal components were measured by X-Ray Fluorescence (XRF) analysis.
Equipment and chemicals
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2.2.
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XRF analysis (using Rigaku ZSX Primus II) was used to determine the chemical compositions of the concentrate, calcines and residues after leaching whereas their structures were determined by X-Ray Diffraction (XRD) analysis (Cu-tube60kv 50Ma, Phillips). Cation
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concentrations of leach liquors were measured by ICP-MS (Agilent A5500) whereas anions
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(SO4, F) were analysed using Ion Chromatography (ICS-2000, Dionex). A muffle furnace was used for batch-roasting. Heating mantles and hot plates were used for leaching
Experimental techniques
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2.3.
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experiments. All chemicals used in the study were of analytical grade.
In this study, lithium was extracted from lepidolite via roasting and then recovered by water leaching. During roasting, the concentrate was mixed with iron sulphate and calcium oxide at different molar ratios of SO4/Li (1:1 to 3.5:1) and Ca/F (0.5:1 to 2:1). They were thoroughly mixed before being poured into ceramic crucibles and then placed into the preheated muffle furnace for roasting. Two types of roasting were carried out including a closed system in which the crucibles were slightly covered by caps to ensure the gases liberated from the decomposition of FeSO4.7H2O do not quickly escape into the furnace atmosphere. The other was an open system in which there was no cap used. Various durations from 0.5 to 2 hours were selected for roasting. A temperature range of 800–950 oC was set for the tests. After roasting, the calcines were cooled to laboratory temperature (20-22 oC) before being manually ground. Finely ground samples were then subjected to water leaching to determine the leachability of Li species.
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Leaching was conducted at various temperatures ranging from 20 oC to 85 oC for 1 h. Magnetic bar stirrers were used for tests carried out at laboratory temperature whereas
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heating mantles with motored stirrers were used for high temperature leaching. A correctly
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weighed calcine sample (10-30 g) was introduced into a known amount of water (30-100 g) at liquid to solid mass ratios varying from 1:1 to 10:1. Preliminary tests showed that a steady
Results and discussion
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3.
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state was reached after 15 minutes. All leaching experiments were conducted in duplicate.
To investigate the effect of SO2/SO3 gases generated from the decomposition of iron sulphate,
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which were believed to play an important role in the extraction of lithium from lepidolite, two types of roasting system were applied as previously mentioned. A comparison of results obtained from roasting tests using both systems was carried out and discussed. In practice
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roasting is commonly conducted in an open system which is easier and more convenient.
Thermodynamic modeling using HSC
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3.1.
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Most of the results reported herewith therefore represented an open roasting system.
HSC program (version 7.1) was used to simulate thermodynamic models for roasting of lepidolite, FeSO4.7H2O and CaO mixtures from which experimental conditions including
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temperature, SO4/Li and Ca/F molar ratios were selected for real tests. The models were set up at the total pressure of 1 bar. As seen in Fig. 1a, the breakdown of lepidolite forms HF while iron sulphate is decomposing to create SO2 and SO3 (in the presence of oxygen) at temperatures of 350-400 oC. The detailed masses and percentages of these gases and other species predicted by HSC are listed in Table 3. It is clearly shown that HSC predicts a total amount of the gases and water vapour that is very close to the loss on ignition (LOI) measured from real tests. According to HSC, the percentages of SO2, SO3 and HF are 16.05%, 9.06% and 1.96% of the total gases and water vapour predicted, respectively. Mass balance of roasting runs conducted at 850 oC based on measured feeds and calcines shows that 2.67 g S (53.8% of total S) and 0.489 g F (79.3% of total F) were present in the gas phase during roasting (Table 4). The high level of these released gases therefore implies that a gas treatment step is required during lepidolite and iron sulphate roasting.
ACCEPTED MANUSCRIPT On the other hand, HSC indicates that Li2SO4 and LiKSO4 are the main lithium compounds formed (total 98% of all Li) from the reaction of lepidolite with iron sulphate at temperatures <900 oC (Fig. 1b). The model shows that the amount of Li2SO4 slightly decreases with the
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steady increase of the LiKSO4 quantity as the temperature rises. Both of them then start
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decomposing at >900 oC while other lithium compounds such as LiAlSiO4, LiAlO2, LiFeO2 begin to form. It is predicted that the formation of these compounds could reduce the
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recovery of lithium during water leaching due to their potentially low solubilities. This was confirmed by the reduction of Li extraction during leaching of calcines yielded from roasting at 925 oC, which will be discussed in detail in the subsequent section. The presence of Li2SO4
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in the calcine was later verified by the XRD pattern as shown in Fig. 9. The easy dissolution
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of Li2SO4 in water was also confirmed by its absence in the residue obtained after leaching. It is indicated that iron sulphate plays a different role compared to sodium sulphate in the interaction with lepidolite during roasting. Na2SO4 seems to be thermally stable and its
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decomposition to form SO2/SO3 takes place at much higher temperatures (750–800 oC)
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compared to iron sulphate (350–400 oC) as seen in Figs. 1a, 1c and 1d. For sodium sulphate roasting, (SO2 + SO3)/Li molar ratio of ~0.014 is predicted by HSC at 1000 oC at equilibrium,
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which means that the amount of SO2/SO3 produced is not enough to react with lithium from lepidolite in a gas – solid interaction. In fact, the LOI measured in the previous study on sodium sulphate roasting (Luong et al., 2013) was negligible. SO2/SO3 therefore could not be the main reactant extracting Li from lepidolite during roasting using sodium sulphate. Iron
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sulphate meanwhile is decomposed at a lower temperature and (SO2 + SO3)/Li molar ratio of ~1.87 at equilibrium is predicted at 850 oC. It is believed that the gas – solid interaction hence could be the main reaction mechanism taking place during roasting of lepidolite and iron sulphate.
Based on HSC results, several three-dimensional models were derived to investigate the effect of temperature, SO4/Li and Ca/F molar ratios on the production of major species containing Li, S and F. As shown in Fig. 1a, the formation of HF, SO2 and SO3 during the roasting of lepidolite, FeSO4.7H2O and CaO is unavoidable. Input amounts of iron sulphate and calcium oxide for HSC were therefore changed in order to determine optimal conditions at which the production of HF is minimised and the formation of SO2/SO3 is reasonable. As seen in Fig. 2a, high SO4/Li molar ratios used would create more S in gases as the result
ACCEPTED MANUSCRIPT of FeSO4.7H2O decomposition. An increase of Ca/F molar ratio could reduce the production of S gases possibly due to the preferential formation of CaSO4, which is clearly shown at 800 o
C. At a Ca/F molar ratio of <2:1, the release of HF is at the highest level at this temperature
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(Fig. 2b). The preferential formation of CaF2 could be the reason for the decrease of HF at
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higher Ca/F molar ratios. However, at higher temperatures (900 and 1000 oC) HSC predicts that more SO2, SO3 and HF are produced. The decomposition of CaSO4 and transformation of
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CaF2 at such temperatures are the reasons for the higher release of the gases from the roasting (Fig. 1a). In addition, the conversion of Li2SO4 and LiKSO4 to other Li species including
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LiFeO2, LiAlSiO4, etc. at high temperatures is also observed (Fig. 1b). Yielded amounts of Li2SO4 and LiKSO4 predicted by HSC are also shown in the 3D models
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(Fig. 3). As seen in Fig. 3a, roasting temperature has a significant influence on the formation of Li2SO4. An increase of temperature from 800 oC to 1000 oC at all SO4/Li molar ratios reduces its production. This could be explained by the transformation of Li2SO4 to other
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lithium compounds as mentioned previously. At low temperatures and Ca/F molar ratios of
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0.5:1 and 1:1, the creation of Li2SO4 seems to be independent on the increase of SO4/Li molar ratio. Only at 2:1 ratio of Ca/F, low ratios of SO4/Li would not produce the maximum amount
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of Li2SO4, which might be due to the preferential formation of CaSO4, thus reducing the quantity of SO2/SO3 required for Li extraction during roasting. The dependence of LiKSO4 on temperature is slightly different from that of Li2SO4 (Fig. 3b). It is shown that LiKSO4 increases in the range of 800–900 oC then starts decreasing at >950 oC. The change of SO4/Li
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molar ratios from 1:1 to 3.5:1 also does not seem to significantly affect the formation of LiKSO4 at low temperatures. Roasting temperature thus is the more important factor compared to Ca/F ratio in controlling the formation of Li2SO4 and LiKSO4 as well as the subsequent recovery of Li during leaching as a result.
HSC and three-dimensional models therefore provided an overview on the effect of temperature, SO4/Li and Ca/F molar ratios on the production of S-, F-containing gases and Li species. There is an indication that roasting at temperatures of >900 oC would enhance the formation of the gases (thus favouring the extraction of Li during roasting) but also reduce amounts of Li2SO4 and LiKSO4 created (due to the conversion to less soluble Li species) especially at low SO4/Li ratios (Fig. 3a). The increasing addition of CaO represented by the increase of Ca/F molar ratios plays an important role in decreasing both S and F gases. High Ca/F molar ratios however might cause a drop in the extraction of Li as less SO2/SO3 is
ACCEPTED MANUSCRIPT formed due to the preferential formation of CaSO4 instead. Hence, the optimum addition of CaO to mixtures of lepidolite and FeSO4.7H2O for roasting should be considered carefully.
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From HSC modelling the optimum conditions for each parameter were selected for Temperature of 800–900 oC to maximise the extraction of Li2SO4 and LiKSO4 and lower the release of SO2, SO3 and HF, -
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conducting roasting experiments as follows:
SO4/Li molar ratio of > 2.5:1 to produce enough SO2/SO3 for the reaction with Li and formation of Li2SO4 and LiKSO4 during roasting,
Ca/F molar ratio of > 2:1 to minimise HF. However a Ca/F molar ratio of >1:1,
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especially at lower temperature (800 oC), would reduce the amounts of SO2/SO3 gases
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produced.
These conditions are almost conflicting with each other so a well balance set of conditions
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(temperature, SO4/Li and Ca/F molar ratios) has to be chosen to maximise the Li recovery. It
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seems that it is unavoidable not to liberate SO2/SO3 and HF under conditions for the maxium Li extraction (predicted to be 98%) in the form of soluble Li2SO4 and sparingly soluble
3.2.
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LiKSO4.
Roasting tests
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3.2.1. Reaction mechanism and effect of SO4/Li molar ratio The amount of SO2/SO3 formed from FeSO4.7H2O roasting with lepidolite is one of the key factors controlling the extraction of lithium from lepidolite. It is believed that the gas will react with lepidolite to extract lithium as Li2SO4 and LiKSO4. The main reactions taking place during the roasting process as derived from HSC were predicted as follows:
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FeSO4.7H2O FeSO4 + 7H2O
(Eq. 1)
12FeSO4 + 3O2 4Fe2(SO4)3 + 2Fe2O3
(Eq. 2)
Fe2(SO4)3 Fe2O3 + 3SO3
(Eq. 3)
KLi2AlSi4O10F(OH) + SO3 Li2SO4 + LiKSO4 + LiAlSiO4 + LiAlO2 + HF (Eq. 4)* (*) Main products can be found from HSC prediction (Figs 1a&b). The reaction is shown in the unbalanced form.
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There is an indication that the total pressure of the roasting system had an influence on the Li extraction. As seen in Fig. 4, HSC predicts that a reduction of the total pressure could lower
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the lithium recoverability from lepidolite. The amounts of Li2SO4 and LiKSO4 formed will be
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reduced when the total pressure drops below 0.5 bar, leading to a decrease of the total Li recovery from ~98% to ~60%. Such a low total pressure implies that lower partial pressures
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of SO2/SO3 in a close-to-vacuum or open system would reduce the Li recovery. In fact, only ~85% Li was extracted during tests conducted in an open environment. In contrast, roasting in a closed system (represented by total pressure > 1bar) by covering the crucibles could
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minimise the loss of SO2/SO3 to the furnace atmosphere, leading to a much higher Li
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extraction (~93%) as shown in Fig. 5.
An increase of SO4/Li molar ratios would enhance the extraction of lithium from lepidolite in which ~85% Li recovery was achieved at the ratio of 3:1 within 0.5 h roasting in an open
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environment (Fig. 5). SO4/Li molar ratios < 3:1 were found to be insufficient for completely
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extracting lithium from lepidolite. Higher ratios (> 3:1) however could not extract more lithium but would create more wasted S gases as predicted by HSC. The poor matching
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between the HSC prediction (at 1 bar) and real experimental results obtained from the open roasting at low SO4/Li molar ratios (Fig. 5) could be due to slow reaction kinetics and escaping SO2/SO3 as previously mentioned. However, the gap is narrowed when a closed system roasting was used. A lithium recovery of ~93% was achieved from closed system
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tests conducted for 1.5 h. The role of roasting time in increasing the extraction of lithium is subsequently reported.
As suggested by Li et al. (2010 and 2011) the extraction of metal ions such as Na, Ca, etc. from aluminosilicates (albite, anorthite) as metal sulphates is via the reaction with SO2/SO3 produced from the decomposition of potassium peroxodisulphate (K2S2O8). These gases are also created from the breakdown of iron sulphate at 350 – 400 oC during roasting with lepidolite in this study. As confirmed by HSC modelling, such a reaction mechanism is therefore believed to play the main role in the extraction of Li from the lepidolite.
3.2.2. Effect of roasting time
It was evident that roasting time did not much affect the extraction of lithium from lepidolite
ACCEPTED MANUSCRIPT when the open system was used (Fig. 6). Roasting for long time seemed to be unnecessary if the gases quickly escaped. Meanwhile, there is a dependence of the lithium extraction on roasting time when the closed system was applied. Increasing time from 0.5 h to 1.5 h sharply
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enhanced the recovery of lithium with the highest of ~93% Li achieved at the longer duration.
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3.2.3. Effect of roasting temperature
According to HSC, roasting at high temperatures >900 oC could reduce amounts of Li2SO4 and LiKSO4 produced due to their decomposition. The transformation of such lithium soluble
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compounds to other insoluble species including LiFeO2, LiAlSiO4 and LiAlO2 is predicted by HSC as shown in Fig. 1b. Li2SO4 and LiKSO4 play the main role in the complete release of
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Li during water leaching. Their lower formation during roasting at >950 oC would certainly lead to the decrease in the overall recovery of Li. As shown in Fig. 7, roasting at <850 oC could not result in a high extraction of lithium whereas >900 oC roasting also decreases Li
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recovery. The range of 850 – 900 oC is the best for Li extraction, which fits well with the
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prediction from HSC.
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3.2.4. Effect of Ca/F molar ratio
The addition of CaO into mixtures of lepidolite and iron sulphate during roasting aims to decrease the formation of HF escaped into the atmosphere and/or soluble F salts which causes
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high levels of F in leach liquors by forming insoluble CaF2. HSC predicts that high molar ratios of Ca/F are required to hinder the liberation of HF if high SO4/Li molar ratios are used as seen in Fig. 2b. To achieve high extractions of Li in real tests, SO4/Li molar ratios of ≥ 3:1 are required. Using large additions of CaO is therefore necessary in this case. The effect of Ca/F molar ratio on the Li extraction is illustrated in Fig. 8.
Mass balance for F amounts contained in lepidolite and calcines based on XRF analysis was used to identify the effect of CaO quantity added on the liberation of F in the form of gases (possibly mainly HF) during roasting. There is indication that when no CaO was used, most of F (~96%) contained in lepidolite was liberated in the gaseous form. The creation of Fcontaining gases in real tests was quickly reduced by the increase of CaO used as the Ca/F molar ratio was increased from 0:1 to 2:1 (Fig. 8). The important role of CaO in capturing F is therefore undeniable. However, an increase of Ca/F molar ratio >1:1 unfortunately would
ACCEPTED MANUSCRIPT lead to the decrease of Li extracted. This might be due to the preferential formation of CaSO4 from CaO, which could lessen the production of SO2/SO3 for the extraction of Li from lepidolite, as indicated in the three-dimensional models (Fig. 2a). Hence, the Ca/F ratio of 1:1
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was chosen to optimally recover Li as well as liberating an acceptable amount of F.
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Nevertheless, a system used to adsorb the F gases should be designed in practice (for example, using Ca(OH)2, CaCl2, etc.) to prevent their liberation into the atmosphere. Leaching the
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calcines obtained from roasting using the Ca/F ratio of 1:1 yielded leach liquors containing ~1% F while ~79% F was liberated as gases (Table 4, 5). The remaining amount of F might
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be contained in CaF2 as confirmed in the XRD pattern of Fig. 9.
XRD patterns of the calcine and the residue after leaching (Fig. 9) show that they mainly
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contain Fe2O3 and other major insoluble compounds including CaSiO3, CaSO4, CaF2, etc. Li2SO4 and Rb2SO4 are major soluble Li and Rb species existing in the calcine, which are completely dissolved during leaching. The presence of these compounds fits well with the
Leaching tests
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3.3.
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prediction of HSC as shown in Fig. 1b.
3.3.1. Effect of water/calcine mass ratio
Leaching at different water/calcine mass ratios from 1:1 to 10:1 yielded almost the same
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recovery of lithium as shown in Fig. 10, with low concentrations of Li obtained at high water/calcine mass ratios. Using Na2SO4 mixed with lepidolite in roasting, Luong et al. (2013) reported that there was a dependence of the Li extraction on water/calcine mass ratios used in leaching. The low solubility of LiKSO4 and LiF was the reason for the difficult dissolution of Li values from the calcines produced by sodium sulphate roasting. The insignificant amount of F contained in leach liquors in this study (Table 5) at 1:1 mass ratio of water/calcine would minimise the effect of LiF in limiting the dissolution of Li in this case. Concentrations of 0.15-0.19 g/L F, corresponding to 0.96-1.2% F recoveries as soluble species were obtained from calcines produced from iron sulphate roasting, whereas 1.14 g/L F, corresponding to 94.8% F recovery was yielded using sodium sulphate in the last study (Luong et al., 2013). In addition, the XRD pattern of the calcine obtained from lepidolite and iron sulphate roasting (Fig. 9) shows that Li2SO4 is the main existing soluble Li compound. Using calcines obtained from the open and closed system roasting and leaching at 1:1 mass ratio of water/calcine, a
ACCEPTED MANUSCRIPT maximum of ~85% and ~93% Li were recovered with high concentrations of ~7.9 g/L and ~8.7g/L Li, respectively. The results are very good when being compared to much lower Li concentrations obtained in most previous studies reported and listed in Table 1. This is
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considered an important improvement as a concentrated Li liquor produced from the process
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would be easily processed. In the case of Na2SO4 roasting, high amounts of H2O must be used to achieve high recoveries of Li, which are accompanied by low Li concentrations. A Li
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concentration stage is therefore necessary (such as evaporation, ion exchange, etc.) before Li2CO3 is produced. In practice, evaporation (more than 10-folds to achieve Li up to 3M Li for Li2CO3 precipitation) requires a high energy input whereas high contents of Na in leach
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liquors prevent the efficient concentration and recovery of Li by ion exchange resins. The lithium recoveries of ~85% and ~93% obtained from the open and closed roasting systems,
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respectively as well as the above advantages are the reasonable motivations to choose iron sulphate as a reactant instead of sodium sulphate.
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3.3.2. Effect of leaching temperature
Leaching temperature also controlled the release of Li when Na2SO4 was used as the
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sulphation agent (Luong et al., 2013). Calcines obtained from Na2SO4 and lepidolite roasting required high temperature (85 oC) for maximally extracting lithium. On the contrary, an independence of the Li extraction on leaching temperature for calcines obtained from iron sulphate roasting in the open system was observed, as documented in Fig. 11. An average of
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85% Li recovery was obtained at the laboratory temperature (~20oC) whereas leaching at higher temperatures also produced the same results. The absence of LiF and the low LiKSO4 contained in calcines could be the main reason for that difference.
3.3.3. Effect of leaching time
As shown in Fig.12, a steady state for the lithium extraction was quickly obtained after 15 minutes of leaching. Li2SO4, the main soluble lithium compound, seemed to be easily dissolved into water. The maximum extraction of lithium at ~85% was achieved during leaching at room temperature using the water/calcine mass ratio of 1:1 in which the calcine was obtained from the open roasting system.
ACCEPTED MANUSCRIPT
Conclusions
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4.
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HSC modelling and three-dimensional models built from its results outlined the effect of key factors including temperature, SO4/Li and Ca/F molar ratios on the extraction of lithium from
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lepidolite as well as the production of S- and F-containing gases during roasting. HSC predicted the best conditions for Li extraction during sulphation as 800-900 oC and SO4/Li molar ratios >2.5:1. A Ca/F molar ratio of >2:1 would minimise the generation of HF,
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although this would cause a lower formation of SO2/SO3 required for Li extraction, especially at a low SO4/Li molar ratio. Using optimum conditions predicted by HSC, roasting tests were
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carried out to produce calcines that were then leached to recover Li. A leach liquor containing a high concentration of ~8.7 g/L Li, corresponding to ~93% Li recovery was yielded from leaching of calcines roasted at 850 oC for 1.5 h in a closed system. Meanwhile, roasting in an
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open system for 0.5-2 h yielded ~83-85% Li recoveries and liquors containing ~7.7-7.9 g/L
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Li were produced. SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively were the best choices for the materials used in roasting. Such the results were obtained at the water/calcine
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mass ratio of 1:1 and room temperature leaching. Recovery of Li from lepidolite using iron sulphate is therefore better compared to sodium sulphate as a roasting additive.
Acknowledgement
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5.
This study was supported by a research grant from Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), Ministry of Knowledge Economy, Korea (No. 2010 T100100408).
ACCEPTED MANUSCRIPT REFERENCES Crocker, L., Lien, R.H. and Others, 1987. Lithium and its recovery from low-grade Nevada clays, pub: US Bureau of Mines, Department of Interior, Bulletin 691. Accessed on 2 October
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2011, http://digicoll.manoa.hawaii.edu/techreports/PDF/USBM-691.pdf. Galaxy Resources Ltd., 2008, 2010. Accessed on 2 November 2011.
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http://www.galaxyresources.com.au/documents/GXY03LithiumCarbonateTestworkResults.p df
http://www.galaxyresources.com.au/project_jiangsu.shtml
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http://metalsplace.com/news/articles/33315/galaxy-resources-ups-lithium-ore-reserves-by-23/
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Guo, X.Y., Li, D., Park, K.H., Tian, Q.H., Wu, Z., 2009. Leaching behavior of metals from a limonitic Ni laterite using a sulphation roasting-leaching process. Hydrometallurgy, 99, 144150.
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Güntner, J., Hammerschmidt, J., 2012. Sulphating roasting of copper-cobalt concentrates. J. S.
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Afr. Inst. Min. Metall, 112, 455-460.
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HSC Chemistry software, Version 7.1, Outotec, 2011. Jandová, J., Vu, H.N., Belková, T., Dvořák, T., Kondás, J., 2009. Obtaining Li2CO3 from zinnwaldite wastes. Ceramics-Silikáty, 53(2), 108-112.
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Jandová, J., Dvořák, P., Vu, H.N., 2010. Processing of zinnwaldite waste to obtain lithium carbonate. Hydrometallurgy, 103, 12-18. Kondás, J., Jandová, J., 2006. Lithium extraction from zinnwaldite wastes after gravity dressing of Sn-W ores. Acta Metallurgica Slovaca, 12, 197-202. Li, E.Y., Chareev, D.A., Shilobreeva, S.N., Grichuk, D.V., Tyutyunnik, O.A., 2010. Experimental study of sulphur dioxide interaction with silicates and aluminosilicates at temperatures of 650 and 850 oC. Geochemistry International, 48, 10, 1039 – 1046. Li, E.Y., Grichuk, D.V., Shilobreeva, S.N., Chareev, D.A., 2011. Interaction between (alumino) silicates and SO2 – containing gas: experiment and thermodynamic model. Vestnik Otdelenia nauk o Zemle RAN, 3, NZ6064, doi:10.2205/2011NZ000194. Luong, V.T., Kang, D.J., An, J.W., Kim, M.J., Tran, T., 2013. Factors affecting the extraction
ACCEPTED MANUSCRIPT of lithium from lepidolite. Hydrometallurgy, 134-135, 54-61. Siame, E., Pascoe, D., 2011. Extraction of lithium from micaceous waste from china clay
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production. Minerals Engineering, 24, 1595-1602.
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Sitando, O., Crouse, P.L., 2012. Processing of a Zimbabwean petalite to obtain lithium
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carbonate. International Journal of Mineral Processing, 102-103, 45-50. Roskill Information Services Ltd, The Economics of Lithium, 2009. pub: United Kingdom, 01 February 2009, Eleventh Edition, ISBN 0862145554.
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Yan, Q., Li, X., Wang, Z., Wu, X., Guo, H., Hu, Q., Peng, W., 2012a. Extraction of lithium from lepidolite by sulphation roasting and water leaching. Journal of Int. Mineral Processing,
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110-111, 1-5.
Yan, Q., Li, X., Wang, Z., Wu, X., Guo, H., Hu, Q., Peng, W., Wang, J., 2012b. Extraction of
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valuable metals from lepidolite. Hydrometallury, 117-118, 116-118.
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USGS - US Geological Survey, 2013. Mineral Commodity Summaries – Lithium, pub: USGS, Virginia, January 2013. 94-95, ISBN 978–1–4113–3548–6.
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Wang, M.Y., Wang, X.W., 2010. Extraction of Mo and Ni from carbonaceous shale by
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oxidative roasting, sulphation roasting and water leaching. Hydrometallurgy, 102, 50-54.
ACCEPTED MANUSCRIPT List of Tables Table 1. Experimental profiles and results of several published studies on processing of Li
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from mineral sources.
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Table 2. Composition (%) of the lepidolite concentrate by XRF and ICP – AES.
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Table 3. Loss on ignition (LOI) obtained from three real tests and produced gases predicted by HSC. Used materials: lepidolite concentrate: 20 g, FeSO4.7H2O: 43.02 g, CaO: 1.82 g and roasting temperature of 850 oC.
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Table 4. Mass balance for roasting at 850 oC (analysis of S and F by XRF). Table 5. Typical major components and concentrations (g/L) of leach liquors and extractions
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(%) from tests using water/calcine mass ratio of 1:1 at room temperature. Calcine from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively in different roasting
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systems.
ACCEPTED MANUSCRIPT Table 1: Experimental profiles and results of several published studies on processing of Li
Mineral tested Li % K% F% Best roast temp, oC Roasting time, h
Lepidolite 2.55 9.31 3.69
Siame & Pascoe, (2011) Zinnwaldite 0.96 7.94 3.36
1000
850
850
880
950
825
1
0.5
0.5
1
1
Additives
Na2SO4
Na2SO4
Na2SO4,K2SO4, CaO
Na2SO4, CaCl2
CaSO4, Ca(OH)2
CaCO3
H2SO4 (300oC, 2nd stage)
85
85
ambient
ambient
90
90-95
50
0.5
0.5
0.5
0.5
0.5
2-18:1
10:1
2.5:1
0.8:1
10:1
5:1
7.5:1
~90
>90
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from mineral sources.
~90
96
~90
97.3
1-3
Expected to be ~1
4.39
8.53
0.69
0.4
5.7
Jandová et al, (2010)
Sitando & Crouse (2012)
Lepidolite 2.00 6.50 4.46
Lepidolite 2.00 6.50 4.46
Zinnwaldite 1.4 6.62 unreported
Zinnwaldite 1.21 10.97 unreported
Petalite/lepidolite 1.9 0.37 0.01 1100 (1st stage)
~90
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Jandová et al, (2009)
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3
Yan et al, (2012b)
2
1
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Best leach temp, oC Leaching time, h Water/calcine ratio Max. Li Extract., % Liquor Li concentration, g/L
0.5
Yan et al, (2012a)
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Luong et al, 2013
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Table 2. Composition (%) of the lepidolite concentrate by XRF and ICP – AES SiO2 Al2O3 Fe2O3 P2O5 Na2O K2O MgO CaO MnO Rb2O Cs2O Li 57.7 22.9 0.17 0.34 0.80 9.15 0.47 1.91 0.13 0.81 0.25 1.79
F 3.08
ACCEPTED MANUSCRIPT Table 3. Loss on ignition (LOI) obtained from three real tests and produced gases predicted by HSC. Used materials: lepidolite concentrate: 20 g, FeSO4.7H2O: 43.02 g, CaO: 1.82 g and
Experiments LOI SO2 (gas)
4.25
SO3 (gas) H2O (gas) HF (gas) LiF (gas)
9.06
19.31
72.92
0.52
1.96
0.00034
0.0013
0.0000019 26.48
0.0000072 100
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Li2F2 (gas) Total
16.05
2.40
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HSC
Percentage (%)
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26.6 ± 0.3
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Mass (g)
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roasting temperature of 850 oC.
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Table 4. Mass balance for roasting at 850 oC (Analysis of S and F by XRF) Component
Mass (g)
S (g)
F (g)
20.00
0
0.617
FeSO4.7H2O
43.02
4.96
0
CaO
1.82
0
0
64.84
4.96
0.617
HSC
26.48
3.09
0.494
Experiment
26.25
2.67* (53.8%) 2.29
0.489* (79.3%) 0.128
Roasting
Feed
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Lepidolite concentrate
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Total
Gases (SO2, HF, SO3, etc) + H2O (vap)
Product Calcine Total (Exp. Gases+Calcines)
38.59 64.84
* Calculated from: Total (S or F in Feed) – S or F in Calcine
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Table 5. Typical major components and concentrations (g/L) of leach liquors and extractions (%) from tests using water/calcine mass ratio of 1:1 at room temperature. Calcine from roasts
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at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively in different roasting
1.0
17.6
0.03
0.15
0.21
82.2
0.19
21.6
32.3
44.1
0.07
10.1
38.1
29.3
1.2
7.9
1.1
0.2
85.4
28.6
17.3
8.7
1.3
93.3
33.2
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0.3
Cs
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Closed system, 1.5 h
0.14
Rb
Na
K
Ca
Mg
Mn
SO4
F
0.8
13.4
0.03
0.20
70.4
0.15
27.1
34.2
0.07
9.59
36.5
25.4
0.96
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Open system, 0.5 h
Concentration (g/L) Extraction (%) Concentration (g/L) Extraction (%)
Li
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Roasting condition
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systems.
ACCEPTED MANUSCRIPT List of Figures Fig. 1. HSC models for (a) and (b): roasting mixture of lepidolite concentrate (20 g), FeSO4.7H2O (43.02 g) and CaO (1.82 g), corresponding to SO4/Li and Ca/F molar ratios of
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3:1 and 1:1, respectively; (c) and (d): roasting mixture of lepidolite and Na2SO4 from Luong
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et al. (2013), therein “dot curves” represent for Na2SO4 roasting only (without lepidolite).
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Equilibrium pressure was set at 1 bar.
Fig. 2. Three-dimensional models showing the relationship of SO4/Li and Ca/F molar ratios with amounts of S and F contained in escaped gases during roasting of 20 g lepidolite (0.026
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mol), FeSO4.7H2O (0.026-0.156 mol, corresponding to 0.5-3:1 SO4/Li molar ratio) and CaO (0.016-0.224 mol, corresponding to 0.5-7:1 Ca/F molar ratio) at different temperatures.
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Fig. 3. Three-dimensional models showing the relationship of temperature, SO4/Li molar ratio and recoverable mass of two major Li species (Li2SO4 and LiKSO4) at different Ca/F
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molar ratios. Conditions as in Fig. 2.
Fig. 4. Effect of total pressure on lithium recoverability based on HSC prediction. Simulation
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using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC.
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Fig. 5. Effect of SO4/Li molar ratio on Li extraction. (a) and (b) this study - calcines from roasts using Ca/F molar ratio of 1:1 at 850 oC in open and closed system, respectively; (c) this study – HSC prediction at 850 oC and 1 bar pressure; (d) and (e) - real results and HSC
pressure.
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prediction for sodium sulphate roasting from Luong et al. (2013) at 1000 oC and 1 bar
Fig. 6. Effect of roasting time on Li extraction. Calcines from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1. Fig. 7. Effect of roasting temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1 in open system, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1. Fig. 8. Effect of Ca/F molar ratio on Li extraction and F liberation during roasting. Calcines from roasts using SO4/Li molar ratio of 3:1 at 850 oC for 0.5 h in open system and leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
ACCEPTED MANUSCRIPT Fig. 9. XRD patterns of (a) lepidolite concentrate, (b) calcine and (c) residue from roast of lepidolite, FeSO4.7H2O and CaO for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching at room temperature for 1 h using
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water/calcine mass ratio of 1:1.
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Fig. 10. Effect of water/calcine mass ratio on Li extraction and concentration. Calcines from
open system. Leaching at room temperature for 1 h.
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roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in
Fig. 11. Effect of leaching temperature on Li extraction. Calcines from roasts for 0.5 h using
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SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching for 1 h using water/calcine mass ratio of 10:1.
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Fig. 12. Effect of leaching time on Li extraction and concentration. Calcine from roast for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system.
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Leaching at room temperature using water/calcine mass ratio of 1:1.
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kmol 4E-05 0.04
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Temperature ( (ooC) Temperature C)
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(d) (d)
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Fig. 1. HSC models for (a) and (b): roasting mixture of lepidolite concentrate (20 g), FeSO4.7H2O (43.02 g) and CaO (1.82 g), corresponding to SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively; (c) and (d): roasting mixture of lepidolite and Na2SO4 from Luong et al. (2013), therein “dot curves” represent for Na2SO4 roasting only (without lepidolite). Equilibrium pressure was set at 1 bar.
FeSO4
5E-06
8E-06 0.008
0.2 600
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Na Na2SO4 (R) 2SO4 (R)
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Fe2(SO4)3
LiKSO4
LiAlO2
Na2SO4(R)
Na 2SO4 Na2SO4
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Na2SO4 Na2SO4
0.0006 0.6
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Li2SO4
LiKSO4
8E-06 0.008
Na Na2SO4 (R) 2SO4 (R) 0.7
0.4
5E-06
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1E-05 0.01
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2E-05
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2E-05 0.02
6E-06 0.006
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CaSiO3
Temperature 1000 C
800
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Temperature (oC)
Na2SO4
Na2SO4
200
mol kmol
0.8
0.0008 0.8
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CaSiO3
Li2SO4
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3E-05
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0E+00 0.00 0 0
CaSO4
800
1E-05
800 800
CaSO4
HF(g)
(c) (c)
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HF (g)
Temperature ( (ooC) Temperature C)
3E-05
Fe2O3
3E-05 0.03
mol
Temperature C
Na2SO4 (R)
4E-05 0.04
SO3(g)
1000
5E-05
SO3 (g)
1000 1000
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Na2SO4 (R)
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1000
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1000 1000
ACCEPTED MANUSCRIPT 1000oC
1000oC 0.50
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2.0 3.5 o Ca/F molar ratio 800 C
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2.0 3.5 Ca/F molar ratio 900oC
S in gases (g)
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2.5 1.5 0.5
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2.0
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Ca/F molar ratio
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Fig. 2. Three-dimensional models showing the relationship of SO4/Li and Ca/F molar ratios
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with amounts of S and F contained in escaped gases during roasting of 20 g lepidolite (0.026 mol), FeSO4.7H2O (0.026-0.156 mol, corresponding to 0.5-3:1 SO4/Li molar ratio) and CaO
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(0.016-0.224 mol, corresponding to 0.5-7:1 Ca/F molar ratio) at different temperatures.
F in gases (g)
2.5
4.0
ACCEPTED MANUSCRIPT Li2SO4
LiKSO4
Ca/F: 2:1
Ca/F: 2:1 0.30 1000 950 900 850 800
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0.13 0.10
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0.13 0.10 1.0
1.5
2.0
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3.5
SO4/Li molar ratio (b)
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Fig. 3. Three-dimensional models showing the relationship of temperature, SO4/Li molar ratio and recoverable mass of two major Li species (Li2SO4 and LiKSO4) at different Ca/F
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molar ratios. Conditions as in Fig. 2.
Li mass (g)
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Li mass (g)
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ACCEPTED MANUSCRIPT 100
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Recoverable Li (%)
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LiKSO4
Li2SO4
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Total Li
Total pressure (bar)
Fig. 4. Effect of total pressure on lithium recoverability based on HSC prediction. Simulation
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using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC.
100
(b)
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(e)
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Extraction (%)
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Exp_iron sulphate_850C_1.5h Exp_iron sulphate_850C_0.5h Exp_sodium sulphate_1000C
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HSC_iron sulphate_850C HSC_sodium sulphate_1000C
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SO4/Li molar ratio
Fig. 5. Effect of SO4/Li molar ratio on Li extraction. (a) and (b) this study - calcines from roasts using Ca/F molar ratio of 1:1 at 850 oC in open and closed system, respectively; (c) this study – HSC prediction at 850 oC and 1 bar pressure; (d) and (e) - real results and HSC prediction for sodium sulphate roasting from Luong et al. (2013) at 1000 oC and 1 bar pressure.
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Fig. 6. Effect of roasting time on Li extraction. Calcines from roasts at 850 oC using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively. Leaching at room temperature for 1 h
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Fig. 7. Effect of roasting temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1 in open system, respectively. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
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1.5
2.0
0
2.5
NU
0.0
Ca/F molar ratio
MA
Fig. 8. Effect of Ca/F molar ratio on Li extraction and F liberation during roasting. Calcines from roasts using SO4/Li molar ratio of 3:1 at 850 oC for 0.5 h in open system and leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
D
800 800 30000
600 600 20000 20000
TE
800
CaSiO KLi2CaSiO Al1.128 3 3Si3.868O11FH CaSO CaSO 4 4
a)
CaFCaF 2 2 Li2SO Li24SO4
10000
CE P
Counts Counts
800 400 400 600 0 0 10
AC
600 200 200 400 0 0
10
Hematite Fe2Fe O32O3 Hematite Maghemite γ - Fe O32O3 Maghemite γ - 2Fe
30
50
b)
400
Hematite Fe2O3 Fe2O3 Maghemite γ - Fe2O3 γ-Fe2O3
Rb 2Rb SO24SO4 CaSiO3 Hematite Fe2O3 CaSO4 Maghemite γ - Fe2O3 70 CaF 90 2 CaSiO3 Calcine Li 2SO4 CaSO4 Rb 2SO4 CaF2 Li2SO4 Rb 2SO4
200 c)
30
50
70
90 Residue
200
0
10
30
50
70
90
0
10 1 10
30 3 30
50 5 2-Theta 2-Theta
70 7
9 90
Fig. 9. XRD patterns of (a) lepidolite concentrate, (b) calcine and (c) residue from roast of 10
30
50
70
90
lepidolite, FeSO4.7H2O and CaO for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, 2-Theta respectively at 850 oC in open system. Leaching at room temperature for 1 h using water/calcine mass ratio of 1:1.
10
80
8 6
T
60 Extraction
IP
Concentration
40
20 0 0
2
4
6
4
SC R
Extraction (%)
100
Concentration (g/L)
ACCEPTED MANUSCRIPT
8
2 0
10
NU
Water/calcine mass ratio
Fig. 10. Effect of water/calcine mass ratio on Li extraction and concentration. Calcines from
MA
roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching at room temperature for 1 h.
TE
D
100
60
AC
CE P
Extraction (%)
80
40
20
0 0
20
40
60
80
100
Temperature (oC)
Fig. 11. Effect of leaching temperature on Li extraction. Calcines from roasts for 0.5 h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system. Leaching for 1 h using water/calcine mass ratio of 10:1.
10
80
8 6
T
60
Concentration (g/L)
100
IP
Extraction
40
4
Concentration
20 0 0
10
20
30
SC R
Extraction (%)
ACCEPTED MANUSCRIPT
40
50
2 0
60
NU
Time (min)
Fig. 12. Effect of leaching time on Li extraction and concentration. Calcine from roast for 0.5
MA
h using SO4/Li and Ca/F molar ratios of 3:1 and 1:1, respectively at 850 oC in open system.
AC
CE P
TE
D
Leaching at room temperature using water/calcine mass ratio of 1:1.