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Extraction of lithium from β-spodumene using sodium sulfate solution
Hydrometallurgy 177 (2018) 49–56
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Extraction of lithium from β-spodumene using sodium sulfate solution a,⁎
a
a
a
a
Ge Kuang , Yu Liu , Huan Li , Shengzhou Xing , Fujie Li , Hui Guo a b
T
a,b
Institute of Chemical Engineering and Technology, Fuzhou University, Fuzhou 350108, China School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
A R T I C L E I N F O
A B S T R A C T
Keywords: β-spodumene Lithium Autoclave Additive Sodium sulfate Leaching
The anticipated increase in demand for lithium salt brings a growing concern over lithium shortage and environmental problems in the industry of extracting lithium from ores. A closed-loop process for the extraction of lithium from β-spodumene (β-LiAlSi2O6) by leaching with Na2SO4, the by-product of the lithium precipitation process, was proposed. Two kinds of additives (CaO and NaOH) were employed to enhance extraction effect, respectively. The lithium extraction efficiencies were recorded to be 93.30% with CaO addition and 90.70% with NaOH addition, which have the more environmentally friendly and economically viable latent capacity in comparison to the currently industrialized sulfuric acid method. By analysis of leaching residue, the extraction mechanism was found to be high-chemoselective ion-exchange between Li+ in β-LiAlSi2O6 and Na+ in Na2SO4 solution.
1. Introduction Lithium, known as the lightest metal, has been widely used in batteries, ceramics, glass, lubricants, aluminum smelting, and polymers (Reichel et al., 2017; Swain, 2017). Particularly, the demand for lithium-ion batteries (LIBs) used in vehicles as power sources have experienced an explosive growth, with the global market share reached 39% in 2016 (Jaskula, 2017; Zou et al., 2013). The worldwide lithium consumption for LIBs in vehicles is expected to increase by 20% per year through 2020 (Jaskula, 2016b). The annual global consumption of lithium, measured in tonnes of lithium carbonate equivalent, reached 170,000 t/year in 2015 and is forecasted to increase to 280,000 t/year in 2020 (Jaskula, 2013, 2016a). Resulting from the increasing demand for lithium, the price of lithium salt has experienced considerable increase. In 2015 alone, the price of spot lithium carbonate has risen by 300% in China and 40–60% worldwide (Jaskula, 2017). Currently, 50% of the lithium produced in the world comes from lithium brines (contain 0.06–0.15% Li) (Friedman-Rudovsky, 2011; Jaskula, 2015; Jandová et al., 2010). However, the lithium brines in the world are located almost exclusively in South America (Grosjean et al., 2012), which may lead to monopolies, and a lithium shortage may emerge in a few decades (Kuang et al., 2015). The Li bearing minerals are distributed more widely in the world, which will be used more effectively. For meeting the growing demand, lithium-bearing minerals, including spodumene, lepidolite and zinnwaldite, have attracted much attention in recent years (Barbosa et al., 2015; Kuang et al., 2015; Speirs et al., 2014; Tarascon, 2010). The spodumene (LiAlSi2O6 or ⁎
Li2O·Al2O3·4SiO2) with the advantage of relatively high theoretical Li content (up to 8.03% Li2O) and comparatively lower process costs has become the preferred mineral for the extraction of lithium (Jaskula, 2016b; Qiu et al., 2016; Rosales et al., 2014). In nature, spodumene exists in the α-phase form and usually associates with quartz and feldspar (Botto, 1985). In most extraction methods, due to the α-phase is resistant to the attack of chemicals. Spodumene is first subjected to a calcination step at 1000–1100 °C for ~1 h to convert spodumene to β-phase that is much more reactive and less resistant to common chemicals (Ellestad and Leute, 1950; Meshram et al., 2014). Table 1 presents the reported methods and their experimental profiles for the extraction of lithium from β-spodumene. Currently, the industrial process for the extraction of lithium from spodumene is sulfuric acid method, which is summarized in Fig. 1 (Meshram et al., 2014; Rosales et al., 2016; Tian et al., 2011; Xiao et al., 1997). In this method, sulfuric acid is used to roast β-spodumene at a temperature around 250 °C according to Eq. (1). The roasted product is then leached with dissolve the metal sulfates. In this process a significant amount of CaCO3 is used to neutralize excess H2SO4 and adjust pH value for removing impurities. Next, Na2CO3 is introduced to the concentrated solution to precipitate Li2CO3 as represented by Eq. (2). However, the sulfuric acid process is performed in rotary kiln, which is not easy with temperature controlling and energy recovering, and additional processes with heavy investments are also required for the disposal of mother solution to recover residual lithium and unprofitable Na2SO4. The recovery efficiency of lithium from β-spodumene in this method conducted is reported to be around 90% (Zhu et al., 2008; Zhang and
Corresponding author. E-mail address: [email protected] (G. Kuang).
https://doi.org/10.1016/j.hydromet.2018.02.015 Received 3 August 2017; Received in revised form 12 February 2018; Accepted 24 February 2018 Available online 26 February 2018 0304-386X/ © 2018 Published by Elsevier B.V.
Hydrometallurgy 177 (2018) 49–56 (Meshram et al., 2014; Tian et al., 2011; Xiao et al., 1997) (Barbosa et al., 2015)
(Barbosa et al., 2013) (Rosales et al., 2014; Rosales et al., 2016)
–
90.2
– 90
Acid gas emission, high concentration reagents.
High leaching temperature, corrosion resistant equipment required.
Roasting with 93% H2SO4 (1.4 times higher than theoretical usage) at 250 °C for 30 min. Roasting with CaCl2 at ore/CaCl2 molar ratio 1:2 and 900 °C for 120 min. Roasting with pure Cl2 at 1100 °C for 150 min. Leaching with 7% HF (S/L ratio 1.82%, w/v) at 75 °C for 20 min. Autoclaving with Na2CO3 at L/S ratio 4 mL/g, Na/Li ratio 1.25 and 225 °C for 60 min.
β − Li2 O·Al2 O3 ·4SiO2 (s) + H2 SO4 (l) → H2 O·Al2 O3 ·4SiO2 (s) + Li2 SO4 (s)
Li2 SO4 (aq) + Na2CO3 (l) → Li2 CO3 (s) + Na2SO4 (aq) (Chen et al., 2011) First step: 94; second step:91
6.05
7.20
7.25 7.03
6.06
Sulfuric acid method (currently industrialized) Chlorination roasting method
Hydrofluoric acid method
Sodium carbonate method
(1) (2)
In recent years, some novel methods have been proposed as alternatives to the sulfuric acid method, which can be divided into chlorination roasting method (Barbosa et al., 2015, 2013), hydrofluoric acid method (Rosales et al., 2014, 2016) and sodium carbonate method (Chen et al., 2011). However, as shown in Table 1, there are still some drawbacks related to these methods, such as the use of high toxic reagents (Rosales et al., 2014, 2016) and high energy consumption (Barbosa et al., 2015, 2013). According to Chen et al. (2011), the process of extracting lithium from spodumene included two steps after decrepitation. In the first step, lithium was extracted as lithium carbonate in solid phase. Then, the solid phase went through the carbonation process and converted to soluble carbonate. However, this two steps leaching decreased the operability and made the leaching process become more complex. Therefore, the total Li extraction efficiency was only 88%, the recovery of Li by sodium carbonate autoclave process was just around 70% because of lithium lossing. In this study, a novel process for the extraction of lithium from βspodumene using sodium sulfate solution with addition of CaO or NaOH is proposed, which is expected to be more cost-effective, environmentally friendly and straightforward, and to be an alternative to the current industrial process.
Complex steps and high reagents cost.
Li2O % in ore
High toxic reagent, not commercialized yet.
Ref. % Li extraction Drawbacks Main reagents/process
Yan, 2015).
Methods
Table 1 Reported methods and their experimental profiles for the extraction of lithium from β-spodumene.
G. Kuang et al.
2. Materials The β-spodumene used in this study was supplied by Shandong RuiFu Lithium Industry Co., Ltd., (Shandong, China) and is originally from Talison Lithium Pty Ltd. operation (Greenbushes, Australia). The conversion of α-spodumene to β-spodumene is carried out by calcining at 1100 °C for 1 h in a rotary kiln by the supplier to make it transfer to β-phase with the conversion rate of 97%. The X-ray diffraction (XRD, PANalytical-X'Pert PRO) analysis of the spodumene before and after calcination indicates that the ore was initially composed of α-spodumene (α-LiAlSi2O6) and quartz (SiO2) (Fig. 2a) and the α-spodumene was converted into β-spodumene (β-LiAlSi2O6) after calcination (Fig. 2b). The Scanning Electron Microscopy (SEM, Hitach-S4800) shows that the spodumene after calcination was fluffier and contained many smaller particles (Fig. 3). The chemical analysis of the β-spodumene used in this study is given in Table 3. The particle size distribution of the β-spodumene measured by laser diffraction particle size analyzer (Mastersizer 2000, Malvern Instruments Co., Ltd) shows that the D90 particle size (particle diameter at the 90 vol% undersize point in the distribution (Higgins et al., 2003) was 75.225 μm (Fig. 4). 3. Procedures and methods The leaching of β-spodumene was performed by placing β-spodumene/Na2SO4 mixture in a 200 mL autoclave (KCF, Beijing Century Senlong experimental apparatus Co., Ltd., Beijing, China) which is made up of #316 stainless steel. An aqueous solution of 0.15 g Na2SO4/ mL of distilled water was used in these tests. CaO or NaOH (analytical reagent) were introduced into the autoclave to enhance the leaching efficiency. The extraction efficiencies of Li with the CaO or NaOH addition in each test were compared under the same leaching conditions. The effects of different variables, including Na2SO4/ore mass ratio, additive/ore mass ratio, leaching temperature, ore particle size, leaching time and liquid to solid ratio (L/S ratio), on the extraction efficiency of lithium were investigated. In order to gain the different ore particle sizes, the ore was grinded by jet mill (MQP01, Weifang Alpa Powder Technology & Equipment Co., Ltd., Shandong, China) with the different feed rate in a few seconds. Among all the leaching 50
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Fig. 1. Flow chart of the current industrial process for the extraction of lithium from β-spodumene.
Fig. 2. XRD patterns of spodumene before (a) and after (b) calcination. Fig. 4. Particle size distribution of the β-spodumene used in this study.
experiments, the stirring speed was fixed at 300 rpm. After leaching, the autoclave was cooled to room temperature with cooling water for 30 min. The mixture was then taken out and filtrated. The lithium content in the filtrate was measured by Atomic Absorption Spectroscopy (AAS, AA-6880, Shimadzu Co., Ltd). The leaching residues obtained after filtration were dried at 120 °C for 2 h and were then weighted by analytical balance (BS 224S, Sartotius). To measure
the lithium content, the residue was completely digested with 98% sulfuric acid and 40% hydrofluoric acid (Brumbaugh and Fanus, 1954) and was then analyzed by AAS. The XRD and SEM analysis of residues were performed so as to evaluate the structure and components.
Fig. 3. SEM images of spodumene before (a) and after (b) calcination.
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Fig. 5. Effects of various variables on the extraction efficiency of Li. (a) Na2SO4/Ore mass ratio; (b) Additive/Ore mass ratio; (c) temperature; (d) time; (e) L/S ratio; (f) Particle size (D90).
4. Results and discussion 4.1. Leaching of β-spodumene
evaluated Na/Li mole ratio (2.4:1), resulting in lithium extraction efficiency of about 90%. Therefore, the optimum mass ratio of 9:20 (Na/ Li mole: 1.5:1) was chosen for the following experiments.
4.1.1. Effect of Na2SO4/ore mass ratio To study the effect of Na2SO4 addition on the Li extraction efficiency, experiments with different Na2SO4/ore mass ratio (w/w) were conducted with additive/ore mass ratio (w/w, mass ratio between the addition of CaO or NaOH and ore) of 1:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm, leaching time of 3 h and L/S ratio of 7.5 mL/g. The results (Fig. 5a) show that the Li extraction efficiency with addition of CaO was always around 12–17% higher than that with NaOH. While, with the increase of the Na2SO4/ore mass ratio, the variation range of Li efficiency with both CaO and NaOH added was always less than 5%. When the Na2SO4/ore mass ratio increased to 9:20, the Li extraction efficiency with CaO and NaOH addition rose to 90.59% and 75.48%, respectively. However, further increase of the ratio did not result in a clear change of the extraction efficiency. This result was better than (Yan et al., 2012), which considered the
4.1.2. Effect of additive/ore mass ratio To investigate the effect of additive/ore mass ratio on the Li extraction efficiency, experiments were carried out with the mass ratio ranging from 0:20 to 1:20. Other conditions were fixed as follows: Na2SO4/ore mass ratio of 9:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm, leaching time of 3 h and L/S ratio of 7.5 mL/ g. The results (Fig. 5b) show that the use of CaO and NaOH as additives had significant influence on the extraction efficiency of Li. When the additive/ore mass ratio increased from 0:20 (no CaO or NaOH added) to 0.2:20, the extraction efficiency of Li rose by about 58% for both CaO and NaOH addition. When the ratio reached 0.4:20, the Li extraction efficiency peaked at 90.67% for CaO and 87.34% for NaOH. However, with more CaO or NaOH added, there was no obvious change of Li extraction efficiency for CaO addition (stable at around 90%), while that for NaOH decreased to 75.48% at the ratio of 1:20. In order to 52
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Table 2 Results of the ore reacted with additions of CaO and NaOH at different temperature. Na2SO4/ore mass ratio = 9:20; Additive/ore mass ratio = 0.4:20; Leaching time = 3 h; Liquid-solid ratio = 7.5 mL/g and D90 particle size = 75.225 μm. Additives
Mass of ore/g
Temperature/°C
Mass of residue/ g
Residue ratea
Lithium extraction efficiency
CaO
20.0538 20.0112 20.0287 20.0667 20.0033 20.0718 20.0260 20.0473 20.0256 20.0085
150 170 190 210 230 150 170 190 210 230
20.6018 20.5837 21.9313 23.0548 22.9001 20.8640 21.4458 22.6998 22.5528 22.5919
102.73% 102.86% 109.50% 114.89% 114.48% 103.95% 107.09% 113.23% 112.62% 112.91%
21.31% 29.12% 55.33% 89.52% 90.67% 36.62% 66.98% 85.12% 84.96% 87.34%
NaOH
a
Fig. 6. XRD analysis of leaching residue at NaOH/ore mass ratio of 1:20.
Residue rate is the ratio between the weight of residue and ore mineral.
always 3–8% higher than that for NaOH. It is noticeable that the Li extraction efficiency with NaOH addition peaked at 87.34% at leaching time of 3 h followed with a decreased of around 3% until leaching time of 6 h. This result indicates that further leaching time is not favorable for lithium extraction, 3 h seems to be more suitable.
investigate the reasons for the significant reduction of Li extraction efficiency when the mass ratio of NaOH/ore was over 0.4:20, the leaching residue at the NaOH/ore mass ratio of 1:20 was tested by XRD. As can be seen from the result (Fig. 6), the residue was mainly composed of analcime (NaAlSi2O6·H2O), quartz (Si2O) and virgilite (LixAlxSi3−xO6), which means that the excess NaOH addition led to the loss of Li in residue in the form of virgilite. Thus, in the present result, the additive/ore mass ratio of 0.4:20 seems to favour the lithium extraction. To reduce the addition amount of the additives and achieve the high extraction efficiency for both CaO and NaOH, the mass ratio of 0.4:20 was chosen for the following experiments.
4.1.5. Effect of L/S ratio The effect of different L/S ratio was conducted at 230 °C for 3 h with Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20 and D90 particle size of 75.225 μm. The results are plotted in Fig. 5e. With the L/S ratio increasing from 3 to 7.5 mL/g, it is evident that the Li extraction efficiency for CaO was always 2–6% higher than that for NaOH. When the ratio reached 5 mL/g, the extraction efficiency for CaO addition increased to 89.89% and remained stable at the following ratios (only 90.67% at 7.5 mL/g). Whereas, from 5 mL/g to 7.5 mL/g, the Li extraction efficiency for NaOH addition was still increased obviously and peaked at 87.34% at 7.5 mL/g. Since higher L/S ratio means more energy consumption for concentration in the downstream recovery process, the L/S ratio of 5 mL/g for CaO addition and 7.5 mL/g for NaOH addition seem to be advisable. Nevertheless, it should be concerned that a low L/S ratio (below 5 mL/g) for CaO addition inhibits the mass transfer and leads to solid mixtures sticking on the inner surface of the reactor, making them difficulty to be washed out, because of the swelling of CaO. To facilitate the operation of experiment and make a comparison between two additives under the same conditions, L/S ratio of 7.5 mL/g was chosen for both CaO and NaOH addition.
4.1.3. Effect of leaching temperature The effect of leaching temperature on the Li extraction efficiency was investigated in the range of 150 to 230 °C. The other conditions were as follows: Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20, D90 particle size of 75.225 μm, leaching time of 3 h, L/S ratio of 7.5 mL/g. The results were shown in Fig. 5c, which indicates the temperature had considerable influence on the Li extraction. In the experimented temperature range, the Li extraction efficiency jumped from 21.31 to 90.67% for CaO addition and from 36.62 to 87.34% for NaOH addition. There was no obvious difference between the figure for NaOH and CaO after the temperature reached 190 and 210 °C, respectively. Taking into account the energy consumption, 190 °C for NaOH addition and 210 °C for CaO addition are recommended for the leaching of β-spodumene. However, in order to make a comparison between NaOH and CaO addition under the same conditions and at a high Li extraction efficiency, 230 °C was chosen for the following experiments. In order to clearly investigate the relationship between the weight of residue and Li extraction efficiency, the detailed results of Fig. 5c are presented in Table 2. For showing the increase rate of the weight of residue in comparison to the ore materials, the term of residue rate % (the ratio between the weight of residue and ore material) was introduced in the table. As can be seen, with the leaching temperature increasing, the residue rate had a positive correlation with Li extraction efficiency. At the optimum leaching temperature of 230 °C, the residue rate was 114.48% for CaO addition and 112.91% for NaOH addition, and the Li extraction efficiency reached 90.67% and 87.34%, respectively.
4.1.6. Effect of ore particle size Some experiments with different particle sizes of the ore were conducted to investigate its effect on Li extraction efficiency at 230 °C for 3 h with Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20 and L/S ratio of 7.5 mL/g. The particle diameter at the 90 vol% undersize point in the distribution (D90) was the variable used to describe the particle size (Higgins et al., 2003). The results were plotted in Fig. 5f. When the particle size of ore materials decreased from 164.145 to 39.233 μm, the extraction efficiencies of Li experienced sharp rise. While, when the particle size continues decreasing, the Li extraction efficiency dropped slightly and the gap between the figure for CaO and NaOH narrowed. A reasonable explanation is that the decreasing particle size led to the higher surface energy of particles and hence made them easily form agglomerations (Vieceli et al., 2017; Zhang et al., 2010) that inhibited extraction reaction. Agglomeration phenomenon was extraordinarily obvious at the condition of D90 particle size 8.642 μm, as shown in Fig. 7. Since the Li extraction efficiencies for both CaO and NaOH addition peaked at 39.233 μm, further experiments were conducted using ore materials screened at this size. At this particle size, the extraction efficiencies of Li for CaO and NaOH additives were
4.1.4. Effect of leaching time The effect of leaching time was investigated in the range from 2 to 6 h under the following conditions: Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm and L/S ratio of 7.5 mL/g. The results (Fig. 5d) indicate that the leaching time (over 2 h) had relatively slight influence on the extraction efficiency of Li and the figure for CaO was 53
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Fig. 7. SEM images of leaching residue with addition of (a) NaOH and (b) CaO, D90 = 8.642 μm.
Table 3 Compositions (wt%) of the ore and leaching residues. Na2SO4/ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm. Sample
Component (wt%)
Ore Residue from CaO addition Residue from NaOH addition
Li extraction efficiency
Li2O
K2 O
CaO
SiO2
Al2O3
Na2O
MgO
Fe2O3
6.17 0.39 0.53
0.92 0.32 0.28
0.57 1.50 0.21
63.00 54.62 55.42
26.38 21.23 21.85
1.46 11.92 12.24
0.21 0.11 0.082
0.61 0.63 0.50
4.2. Analysis of leaching residue
93.30% and 90.70%, respectively, and the pressure of autoclave was recorded as 2.7 ± 0.1 MPa. Table 3 presents the chemical analysis of leaching residue obtained from the experiment with the highest extraction efficiencies, i.e. 93.30% for CaO addition and 90.70% for NaOH addition. Under the reaction conditions, the mass of leaching residue was around 23.0 g (CaO) or 22.7 g (NaOH). As can be seen from the table, the Li content in residue had decreased from the original value of 6.17% to 0.39 and 0.53% with addition of CaO and NaOH, respectively, and the Na content in residues was risen by over 10% for both additive of CaO and NaOH. According to analyzing, the decreased Li content was equal to the increased Na content in the number of mole. Besides, other components, including K2O, CaO (for NaOH addition), SiO2, Al2O3, MgO and Fe2O3 were also decreased more or less, this might be because the total weight of residue was increased overtaking the weight of ore material as indicated in Table 2.
To confirm the leaching effect with addition of CaO and NaOH, leaching residue obtained from the experiments with the highest extraction efficiencies was tested by SEM (Fig. 8). As shown in Fig. 8a, there are large amount of agglomerations of small particles wrapped around the residue, which may lead to less contact between Na2SO4 solution and ore materials resulting in low extraction efficiency. In contrast, the addition of CaO resulted in the surface of the residue particles being smooth with little agglomeration (Fig. 8b). These observations explain why Li extraction efficiency with NaOH additive was lower than that with CaO additive in some leaching experiments. To investigate the mechanism of the extraction process, the leaching residue was analyzed by XRD. The results (Fig. 9) indicate that the residues with additive of both CaO (Fig. 9a) and NaOH (Fig. 9b) were mainly composed of analcime (NaAlSi2O6·H2O), β-spodumene (βLiAlSi2O6) and quartz (SiO2). Comparing the mineral composition of the reaction materials (Fig. 2), after leaching, the β-spodumene (βLiAlSi2O6) was converted to analcime and the quartz still remained in residue. The result indicates that the extraction process was based on an ion-exchange mechanism, where Li+ in β-spodumene (β- LiAlSi2O6) was replaced by Na+ and leached into solution. The reaction can be represented as:
4.1.7. Reproducibility experiments To confirm the reliability of the leaching result, Three parallel tests were conducted under the following conditions: Na2SO4/additive (CaO or NaOH)/ore mass ratio of 9:0.4:20, leaching temperature of 230 °C, leaching time of 3 h, L/S ratio of 7.5 mL/g and D90 particle size of 39.233 μm. The results are shown in Table 4. The standard deviation with the addition of CaO (0.49%) and NaOH (0.57%) were less than 2%, which indicated that the results are reproducible under the evaluated conditions. The Li extraction efficiency of three parallel tests are not significantly different. This is favorable for further researching the optimum process in our future work.
OH−
2β − LiAlSi2 O6 (s) + Na2SO4 (s) + 2H2 O (l) ⎯⎯⎯⎯⎯→ 2NaAlSi2 O6 ·H2 O (s) + Li2 SO4 (aq)
CaO NaOH
Li extraction efficiency (%) from parallel experiments 1#
2#
3#
92.73 91.10
93.92 90.50
93.18 89.70
Average (%)
Standard deviation (%)
93.28 90.43
0.49 0.57
(3)
From Eq. (3), the weight of solid residue is predicted to be greater than the ore materials, which can account for the residue rate being over 100% and the positive correlation between Li extraction efficiency and residue rate (indicated in Table 2). The ion-exchange based mechanism is similar to that previously reported for methods using sulfuric acid (Xiao et al., 1997) and calcium chloride roasting (Barbosa et al., 2015) to extract lithium from β-spodumene, where Li+ was replaced by H+ and Ca2+, respectively. However, this extraction process was built on strong base transforming to weak base in the alkaline atmosphere. The product analcime can be applied in environmental protection, catalyst preparation and ceramic production, which has been widely researched before. Such as, modified Ni (II) loaded analcime electrode was used to catalyze the electrooxidation of methanol (Azizi et al.,
Table 4 Results of parallel experiments under the conditions of Na2SO4/additive (CaO or NaOH)/ ore mass ratio 9:0.4:20, leaching temperature 230 °C, leaching time 3 h, L/S ratio 7.5 mL/ g and D90 particle size 39.233 μm. Additives
– 93.30% 90.70%
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Fig. 8. SEM images of leaching residue with additive of (a) NaOH and (b) CaO. Na2SO4/ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/ g and D90 particle size = 39.233 μm.
Table 5 Chemical composition of the leaching solution. Na2SO4/ore mass ratio = 9:20, Additive/ ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm. The volume of liquor was 1 L, mass of ore was 40 g. Leaching solution
Solution from CaO addition Solution from NaOH addition
The concentration of components (mg/L) Li2O
Na2O
CaO
SiO2
Al2O3
K2O
MgO
Fe2O3
2293
1860
54.88
126
0.064
91.62
0.15
0.0034
2250
2359
3.28
223
0.038
124.13
0.20
0.0170
Fig. 10. Firstly, β-spodumene is leached in an autoclave with Na2SO4 and associated CaO or NaOH additive. Through filtration, Li+ will remain in solution and Na+ will report to the residue. The filter liquor and washing water were diluted with few distilled water to 1 L together. Table 5 lists the chemical composition of the leaching solution obtained from the experiment with the highest extraction efficiencies. Relatively few impurities in the leaching solution contributed to simplify the purification process, which was a comparatively mature process in the lithium industry (Vieceli et al., 2018; Sitando and Crouse, 2012; Swain, 2017). Some impurities were removed by pH control with lime in leaching liquor, whereafter, redundant Ca2+ was cleaned by adding moderate Na2CO3. After purification and concentration, Li contained in solution could be easily recovered by adding Na2CO3 to form Li2CO3 precipitate according to Eq. (2) (Meshram et al., 2014). This method for precipitating Li has been well studied and is very common in most industrial cases (Meshram et al., 2014; Swain, 2017; Wilkomirsky, 1999; Zhang et al., 1998). Finally, the mother solution mainly containing Na2SO4 obtained after precipitation of Li can be reused to commence the next cycle of autoclave leaching to achieve a closed-loop. Compared with the previously reported methods (Table 1), the suggested process is largely simplified, just involves common chemicals, and the leaching residue can be the reused resource for glass ceramic industry and environmental protection field, which make it cost-effective, eco-friendly and straightforward.
Fig. 9. XRD analysis of leaching residue with additive of (a) NaOH and (b) CaO. Na2SO4/ ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm.
2014), modified zincon loaded analcime to sorb preconcentration of palladium (Taher et al., 2007), the contained F−, NH4+ and Cd2+ in the waste water were separated by synthesis analcime as absorbent or ion-exchange material (Chen, 2015; Yuan et al., 2016; Gu et al., 2008; Wang et al., 2003), and the analcime-bearing ore was as a raw for ceramic industry (Shushkov et al., 2011). So the leaching residue could be recycled for another stage not to be abandoned, under these potential applications the process may be an optionally environment friendly course for extracting Li from β-spodumene. 4.3. A suggested closed-loop process for the extraction and recovery of Li from β-spodumene Based on the preceding results, a closed-loop process for extracting and recovering Li from β-spodumene can be proposed as outlined in
Fig. 10. Flow chart of the suggested closed-loop process for the extraction and recovery of Li from spodumene.
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5. Conclusions
Accessed date: 5 July 2017. Jaskula, B.W., 2015. Lithium, Minerals Yearbook-2015, USGS. Available at. http:// minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2015-lithi.pdf, Accessed date: 10 November 2017. Jaskula, B.W., 2016a. Lithium, Mineral Commodity Summaries, USGS. Available at. https://minerals.usgs.gov/minerals/pubs/commodity/lithium/mcs-2016-lithi.pdf, Accessed date: 5 July 2017. Jaskula, B.W., 2016b. Lithium, Minerals Yearbook - 2014, USGS. Available at. https:// minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2014-lithi.pdf, Accessed date: 5 July 2017. Jaskula, B.W., 2017. Lithium, Mineral Commodity Summaries USGS. Available at. https://minerals.usgs.gov/minerals/pubs/commodity/lithium/mcs-2017-lithi.pdf, Accessed date: 5 July 2017. Kuang, G., Li, H., Hu, S., Jin, R., Liu, S., Guo, H., 2015. Recovery of aluminium and lithium from gypsum residue obtained in the process of lithium extraction from lepidolite. Hydrometallurgy 157, 214–218. Meshram, P., Pandey, B.D., Mankhand, T.R., 2014. Extraction of lithium from primary and secondary sources by pre-treatment, leaching and separation: a comprehensive review. Hydrometallurgy 150, 192–208. Qiu, Y., Wu, D., Yan, L., Zhou, Y., 2016. Recycling of spodumene slag: preparation of green polymer composites. RSC Adv. 6 (43), 36942–36953. Reichel, S., Aubel, T., Patzig, A., Janneck, E., Martin, M., 2017. Lithium recovery from lithium-containing micas using sulfur oxidizing microorganisms. Miner. Eng. 106, 18–21. Rosales, G.D., Ruiz, d.C., Rodriguez, M.H., 2014. Novel process for the extraction of lithium from β-spodumene by leaching with HF. Hydrometallurgy 147, 1–6. Rosales, G.D., Ruiz, M.C., Rodriguez, M.H., 2016. Study of the extraction kinetics of lithium by leaching β-spodumene with hydrofluoric acid. Fortschr. Mineral. 6 (4), 98. Shushkov, D.A., Kotova, O.B., Goldin, B.A., 2011. Geomaterials on the basis of analcimebearing rocks. Geomaterials 1 (2), 33–38. Sitando, O., Crouse, P.L., 2012. Processing of a Zimbabwean petalite to obtain lithium carbonate. Int. J. Miner. Process. 102-103, 45–50. Speirs, J., Contestabile, M., Houari, Y., Gross, R., 2014. The future of lithium availability for electric vehicle batteries. Renew. Sust. Energ. Rev. 35 (0), 183–193. Swain, B., 2017. Recovery and recycling of lithium: a review. Sep. Purif. Technol. 172, 388–403. Taher, M.A., Mostafavi, A., Mobarakeh, S.Z., 2007. Modified analcime loaded with zincon as a useful material for the separation and preconcentration of trace palladium and its determination by third-derivative spectrophotometry. J. Anal. Chem. 62 (11), 1022–1027. Tarascon, J.-M., 2010. Is lithium the new gold? Nat. Chem. 2 (6), 510. Tian, Q., Chen, B., Chen, Y., Ma, L., Shi, X., 2011. Roasting and leaching behavior of spodumene in sulphuric acid process. Chin. J. Rare Metals 1, 025 (In Chinese). Vieceli, N., et al., 2017. Effects of mechanical activation on lithium extraction from a lepidolite ore concentrate. Miner. Eng. 102, 1–14. Vieceli, N., Nogueira, C., Pereira, M., Durão, F., Guimarães, C., Margarido, F., 2018. Recovery of lithium carbonate by acid digestion and hydrometallurgical processing from mechanically activated lepidolite. Hydrometallurgy 175, 1–10. Wang, Y., Guo, Y., Yang, Z., Cai, H., Xavier, Q., 2003. Synthesis of zeolites using fly ash and their application in removing heavy metals from waters. Sci. China Ser. D 46 (9), 967–976. Wilkomirsky, I., 1999. Production of lithium carbonate from brines, US Patent 5993759. Xiao, M., Wang, S., Zhang, Q., Zhang, J., 1997. Leaching mechanism of the spodumene sulphuric acid process. Rare Metals 16 (01), 37–45. Yan, Q., Li, X., Wang, Z., Wu, X., Wang, J., Guo, H., Hu, Q., Peng, W., 2012. Extraction of lithium from lepidolite by sulfation roasting and water leaching. Int. J. Miner. Process. 110-111, 1–5. Yuan, J., Yang, J., Ma, H., Liu, C., 2016. Crystal structural transformation and kinetics of NH4+/Na+ ion-exchange in analcime. Microporous Mesoporous Mater. 222, 202–208. Zhang, M., Yan, Y., 2015. Lithium and Lithium Alloy. Science Press, Beijing (In Chinese). Zhang, P., Yokoyama, T., Itabashi, O., Suzuki, T.M., Inoue, K., 1998. Hydrometallurgical process for recovery of metal values from spent lithium-ion secondary batteries. Hydrometallurgy 47 (2), 259–271. Zhang, Y., Zheng, S., Du, H., Xu, H., Zhang, Y., 2010. Effect of mechanical activation on alkali leaching of chromite ore. Trans. Nonferrous Met. Soc. 20 (5), 888–891. Zhu, Z., Zhu, C., Weng, X., Zhu, G., Ling, B., 2008. Progress in production process of lithium carbonate. J. Salt Lake Res. 4, 64–72 (In Chinese). Zou, H., Gratz, E., Apelian, D., Wang, Y., 2013. A novel method to recycle mixed cathode materials for lithium ion batteries. Green Chem. 15 (5), 1183–1191.
A closed-loop process of extracting and recovery Li from β-spodumene by leaching with Na2SO4 in pressure leaching was proposed. The effects of two kinds of additive (CaO and NaOH) on the extraction efficiency of Li were investigated and compared. Over 90% Li was attained with this process. The highest Li extraction efficiencies, i.e. 93.30% for CaO addition and 90.70% for NaOH, were observed under the following conditions: Na2SO4/additive (CaO or NaOH)/ore mass ratio of 9:0.4:20, leaching temperature of 230 °C, leaching time of 3 h, L/S ratio of 7.5 mL/g and particle size (D90) of 39.233 μm. It was found that significant amount of agglomerations were generated around ore particles when adding NaOH, which may account for its lower extraction efficiency in comparison to adding CaO. By analysis of leaching residue, the extraction reaction was found to be based on ion-exchange between Li+ and Na+, with β-spodumene (β-LiAlSi2O6) converted into analcime (NaAlSi2O6·H2O). Finally, a closed-loop process based on the results of this study for the extraction of Li from β-spodumene was proposed. This work provided an environmentally friendly, possibly cost-effective and comparatively straightforward way to extract lithium from β-spodumene, which has the potential to be industrially developed. Acknowledgements The authors thank the financial support from the National Key Technology R&D Program of China during the 12th Five-year Plan Period (Grant No.2012BAB10B02). References Azizi, S.N., Ghasemi, S., Gilani, N.S., 2014. An electrode with Ni(II) loaded analcime zeolite catalyst for the electrooxidation of methanol. Chin. J. Catal. 35 (3), 383–390. Barbosa, L.I., Valente, N.G., Gonzalez, J.A., 2013. Kinetic study on the chlorination of βspodumene for lithium extraction with Cl2 gas. Thermochim. Acta 557, 61–67. Barbosa, L.I., González, J.A., Ruiz, M.d.C., 2015. Extraction of lithium from β-spodumene using chlorination roasting with calcium chloride. Thermochim. Acta 605, 63–67. Botto, I.L., 1985. Structural and spectroscopic properties of leached spodumene in the acid roast processing. Mater. Chem. Phys. 13 (5), 423–436. Brumbaugh, R.J., Fanus, W.E., 1954. Determination of lithium in spodumene by flame photometry. Anal. Chem. 26 (3), 463–465. Chen, F., 2015. Treatment of fluorine water by porous analcite balls. Conserv. Util. Miner. Resour. 2, 45–49 (In Chinese). Chen, Y., Tian, Q., Chen, B., Shi, X., Liao, T., 2011. Preparation of lithium carbonate from spodumene by a sodium carbonate autoclave process. Hydrometallurgy 109 (1–2), 43–46. Ellestad, R.B. and Leute, K.M., 1950. Method of extracting lithium values from spodumene ores, US Patent 2516109. Friedman-Rudovsky, J., 2011. Dreams of a lithium empire. Science 334 (6058), 896–897. Grosjean, C., Miranda, P.H., Perrin, M., Poggi, P., 2012. Assessment of world lithium resources and consequences of their geographic distribution on the expected development of the electric vehicle industry. Renew. Sust. Energ. Rev. 16 (3), 1735–1744. Gu, B., Shang, Y., Wu, J., Meng, C., 2008. Ion exchange of Cd2+ synthesized analcime. Ion Exchange Adsorpt. 2, 154–162 (In Chinese). Higgins, J.P., et al., 2003. Spectroscopic approach for on-line monitoring of particle size during the processing of pharmaceutical nanoparticles. Anal. Chem. 75 (8), 1777–1785. Jandová, J., Dvořák, P., Vu, H.N., 2010. Processing of zinnwaldite waste to obtain Li2CO3. Hydrometallurgy 103 (1–4), 12–18. Jaskula, B.W., 2013. Lithium, Minerals Yearbook-2012, USGS. Available at. http:// minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2012-lithi.pdf,
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Extraction of lithium from β-spodumene using sodium sulfate solution a,⁎
a
a
a
a
Ge Kuang , Yu Liu , Huan Li , Shengzhou Xing , Fujie Li , Hui Guo a b
T
a,b
Institute of Chemical Engineering and Technology, Fuzhou University, Fuzhou 350108, China School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
A R T I C L E I N F O
A B S T R A C T
Keywords: β-spodumene Lithium Autoclave Additive Sodium sulfate Leaching
The anticipated increase in demand for lithium salt brings a growing concern over lithium shortage and environmental problems in the industry of extracting lithium from ores. A closed-loop process for the extraction of lithium from β-spodumene (β-LiAlSi2O6) by leaching with Na2SO4, the by-product of the lithium precipitation process, was proposed. Two kinds of additives (CaO and NaOH) were employed to enhance extraction effect, respectively. The lithium extraction efficiencies were recorded to be 93.30% with CaO addition and 90.70% with NaOH addition, which have the more environmentally friendly and economically viable latent capacity in comparison to the currently industrialized sulfuric acid method. By analysis of leaching residue, the extraction mechanism was found to be high-chemoselective ion-exchange between Li+ in β-LiAlSi2O6 and Na+ in Na2SO4 solution.
1. Introduction Lithium, known as the lightest metal, has been widely used in batteries, ceramics, glass, lubricants, aluminum smelting, and polymers (Reichel et al., 2017; Swain, 2017). Particularly, the demand for lithium-ion batteries (LIBs) used in vehicles as power sources have experienced an explosive growth, with the global market share reached 39% in 2016 (Jaskula, 2017; Zou et al., 2013). The worldwide lithium consumption for LIBs in vehicles is expected to increase by 20% per year through 2020 (Jaskula, 2016b). The annual global consumption of lithium, measured in tonnes of lithium carbonate equivalent, reached 170,000 t/year in 2015 and is forecasted to increase to 280,000 t/year in 2020 (Jaskula, 2013, 2016a). Resulting from the increasing demand for lithium, the price of lithium salt has experienced considerable increase. In 2015 alone, the price of spot lithium carbonate has risen by 300% in China and 40–60% worldwide (Jaskula, 2017). Currently, 50% of the lithium produced in the world comes from lithium brines (contain 0.06–0.15% Li) (Friedman-Rudovsky, 2011; Jaskula, 2015; Jandová et al., 2010). However, the lithium brines in the world are located almost exclusively in South America (Grosjean et al., 2012), which may lead to monopolies, and a lithium shortage may emerge in a few decades (Kuang et al., 2015). The Li bearing minerals are distributed more widely in the world, which will be used more effectively. For meeting the growing demand, lithium-bearing minerals, including spodumene, lepidolite and zinnwaldite, have attracted much attention in recent years (Barbosa et al., 2015; Kuang et al., 2015; Speirs et al., 2014; Tarascon, 2010). The spodumene (LiAlSi2O6 or ⁎
Li2O·Al2O3·4SiO2) with the advantage of relatively high theoretical Li content (up to 8.03% Li2O) and comparatively lower process costs has become the preferred mineral for the extraction of lithium (Jaskula, 2016b; Qiu et al., 2016; Rosales et al., 2014). In nature, spodumene exists in the α-phase form and usually associates with quartz and feldspar (Botto, 1985). In most extraction methods, due to the α-phase is resistant to the attack of chemicals. Spodumene is first subjected to a calcination step at 1000–1100 °C for ~1 h to convert spodumene to β-phase that is much more reactive and less resistant to common chemicals (Ellestad and Leute, 1950; Meshram et al., 2014). Table 1 presents the reported methods and their experimental profiles for the extraction of lithium from β-spodumene. Currently, the industrial process for the extraction of lithium from spodumene is sulfuric acid method, which is summarized in Fig. 1 (Meshram et al., 2014; Rosales et al., 2016; Tian et al., 2011; Xiao et al., 1997). In this method, sulfuric acid is used to roast β-spodumene at a temperature around 250 °C according to Eq. (1). The roasted product is then leached with dissolve the metal sulfates. In this process a significant amount of CaCO3 is used to neutralize excess H2SO4 and adjust pH value for removing impurities. Next, Na2CO3 is introduced to the concentrated solution to precipitate Li2CO3 as represented by Eq. (2). However, the sulfuric acid process is performed in rotary kiln, which is not easy with temperature controlling and energy recovering, and additional processes with heavy investments are also required for the disposal of mother solution to recover residual lithium and unprofitable Na2SO4. The recovery efficiency of lithium from β-spodumene in this method conducted is reported to be around 90% (Zhu et al., 2008; Zhang and
Corresponding author. E-mail address: [email protected] (G. Kuang).
https://doi.org/10.1016/j.hydromet.2018.02.015 Received 3 August 2017; Received in revised form 12 February 2018; Accepted 24 February 2018 Available online 26 February 2018 0304-386X/ © 2018 Published by Elsevier B.V.
Hydrometallurgy 177 (2018) 49–56 (Meshram et al., 2014; Tian et al., 2011; Xiao et al., 1997) (Barbosa et al., 2015)
(Barbosa et al., 2013) (Rosales et al., 2014; Rosales et al., 2016)
–
90.2
– 90
Acid gas emission, high concentration reagents.
High leaching temperature, corrosion resistant equipment required.
Roasting with 93% H2SO4 (1.4 times higher than theoretical usage) at 250 °C for 30 min. Roasting with CaCl2 at ore/CaCl2 molar ratio 1:2 and 900 °C for 120 min. Roasting with pure Cl2 at 1100 °C for 150 min. Leaching with 7% HF (S/L ratio 1.82%, w/v) at 75 °C for 20 min. Autoclaving with Na2CO3 at L/S ratio 4 mL/g, Na/Li ratio 1.25 and 225 °C for 60 min.
β − Li2 O·Al2 O3 ·4SiO2 (s) + H2 SO4 (l) → H2 O·Al2 O3 ·4SiO2 (s) + Li2 SO4 (s)
Li2 SO4 (aq) + Na2CO3 (l) → Li2 CO3 (s) + Na2SO4 (aq) (Chen et al., 2011) First step: 94; second step:91
6.05
7.20
7.25 7.03
6.06
Sulfuric acid method (currently industrialized) Chlorination roasting method
Hydrofluoric acid method
Sodium carbonate method
(1) (2)
In recent years, some novel methods have been proposed as alternatives to the sulfuric acid method, which can be divided into chlorination roasting method (Barbosa et al., 2015, 2013), hydrofluoric acid method (Rosales et al., 2014, 2016) and sodium carbonate method (Chen et al., 2011). However, as shown in Table 1, there are still some drawbacks related to these methods, such as the use of high toxic reagents (Rosales et al., 2014, 2016) and high energy consumption (Barbosa et al., 2015, 2013). According to Chen et al. (2011), the process of extracting lithium from spodumene included two steps after decrepitation. In the first step, lithium was extracted as lithium carbonate in solid phase. Then, the solid phase went through the carbonation process and converted to soluble carbonate. However, this two steps leaching decreased the operability and made the leaching process become more complex. Therefore, the total Li extraction efficiency was only 88%, the recovery of Li by sodium carbonate autoclave process was just around 70% because of lithium lossing. In this study, a novel process for the extraction of lithium from βspodumene using sodium sulfate solution with addition of CaO or NaOH is proposed, which is expected to be more cost-effective, environmentally friendly and straightforward, and to be an alternative to the current industrial process.
Complex steps and high reagents cost.
Li2O % in ore
High toxic reagent, not commercialized yet.
Ref. % Li extraction Drawbacks Main reagents/process
Yan, 2015).
Methods
Table 1 Reported methods and their experimental profiles for the extraction of lithium from β-spodumene.
G. Kuang et al.
2. Materials The β-spodumene used in this study was supplied by Shandong RuiFu Lithium Industry Co., Ltd., (Shandong, China) and is originally from Talison Lithium Pty Ltd. operation (Greenbushes, Australia). The conversion of α-spodumene to β-spodumene is carried out by calcining at 1100 °C for 1 h in a rotary kiln by the supplier to make it transfer to β-phase with the conversion rate of 97%. The X-ray diffraction (XRD, PANalytical-X'Pert PRO) analysis of the spodumene before and after calcination indicates that the ore was initially composed of α-spodumene (α-LiAlSi2O6) and quartz (SiO2) (Fig. 2a) and the α-spodumene was converted into β-spodumene (β-LiAlSi2O6) after calcination (Fig. 2b). The Scanning Electron Microscopy (SEM, Hitach-S4800) shows that the spodumene after calcination was fluffier and contained many smaller particles (Fig. 3). The chemical analysis of the β-spodumene used in this study is given in Table 3. The particle size distribution of the β-spodumene measured by laser diffraction particle size analyzer (Mastersizer 2000, Malvern Instruments Co., Ltd) shows that the D90 particle size (particle diameter at the 90 vol% undersize point in the distribution (Higgins et al., 2003) was 75.225 μm (Fig. 4). 3. Procedures and methods The leaching of β-spodumene was performed by placing β-spodumene/Na2SO4 mixture in a 200 mL autoclave (KCF, Beijing Century Senlong experimental apparatus Co., Ltd., Beijing, China) which is made up of #316 stainless steel. An aqueous solution of 0.15 g Na2SO4/ mL of distilled water was used in these tests. CaO or NaOH (analytical reagent) were introduced into the autoclave to enhance the leaching efficiency. The extraction efficiencies of Li with the CaO or NaOH addition in each test were compared under the same leaching conditions. The effects of different variables, including Na2SO4/ore mass ratio, additive/ore mass ratio, leaching temperature, ore particle size, leaching time and liquid to solid ratio (L/S ratio), on the extraction efficiency of lithium were investigated. In order to gain the different ore particle sizes, the ore was grinded by jet mill (MQP01, Weifang Alpa Powder Technology & Equipment Co., Ltd., Shandong, China) with the different feed rate in a few seconds. Among all the leaching 50
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Fig. 1. Flow chart of the current industrial process for the extraction of lithium from β-spodumene.
Fig. 2. XRD patterns of spodumene before (a) and after (b) calcination. Fig. 4. Particle size distribution of the β-spodumene used in this study.
experiments, the stirring speed was fixed at 300 rpm. After leaching, the autoclave was cooled to room temperature with cooling water for 30 min. The mixture was then taken out and filtrated. The lithium content in the filtrate was measured by Atomic Absorption Spectroscopy (AAS, AA-6880, Shimadzu Co., Ltd). The leaching residues obtained after filtration were dried at 120 °C for 2 h and were then weighted by analytical balance (BS 224S, Sartotius). To measure
the lithium content, the residue was completely digested with 98% sulfuric acid and 40% hydrofluoric acid (Brumbaugh and Fanus, 1954) and was then analyzed by AAS. The XRD and SEM analysis of residues were performed so as to evaluate the structure and components.
Fig. 3. SEM images of spodumene before (a) and after (b) calcination.
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Fig. 5. Effects of various variables on the extraction efficiency of Li. (a) Na2SO4/Ore mass ratio; (b) Additive/Ore mass ratio; (c) temperature; (d) time; (e) L/S ratio; (f) Particle size (D90).
4. Results and discussion 4.1. Leaching of β-spodumene
evaluated Na/Li mole ratio (2.4:1), resulting in lithium extraction efficiency of about 90%. Therefore, the optimum mass ratio of 9:20 (Na/ Li mole: 1.5:1) was chosen for the following experiments.
4.1.1. Effect of Na2SO4/ore mass ratio To study the effect of Na2SO4 addition on the Li extraction efficiency, experiments with different Na2SO4/ore mass ratio (w/w) were conducted with additive/ore mass ratio (w/w, mass ratio between the addition of CaO or NaOH and ore) of 1:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm, leaching time of 3 h and L/S ratio of 7.5 mL/g. The results (Fig. 5a) show that the Li extraction efficiency with addition of CaO was always around 12–17% higher than that with NaOH. While, with the increase of the Na2SO4/ore mass ratio, the variation range of Li efficiency with both CaO and NaOH added was always less than 5%. When the Na2SO4/ore mass ratio increased to 9:20, the Li extraction efficiency with CaO and NaOH addition rose to 90.59% and 75.48%, respectively. However, further increase of the ratio did not result in a clear change of the extraction efficiency. This result was better than (Yan et al., 2012), which considered the
4.1.2. Effect of additive/ore mass ratio To investigate the effect of additive/ore mass ratio on the Li extraction efficiency, experiments were carried out with the mass ratio ranging from 0:20 to 1:20. Other conditions were fixed as follows: Na2SO4/ore mass ratio of 9:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm, leaching time of 3 h and L/S ratio of 7.5 mL/ g. The results (Fig. 5b) show that the use of CaO and NaOH as additives had significant influence on the extraction efficiency of Li. When the additive/ore mass ratio increased from 0:20 (no CaO or NaOH added) to 0.2:20, the extraction efficiency of Li rose by about 58% for both CaO and NaOH addition. When the ratio reached 0.4:20, the Li extraction efficiency peaked at 90.67% for CaO and 87.34% for NaOH. However, with more CaO or NaOH added, there was no obvious change of Li extraction efficiency for CaO addition (stable at around 90%), while that for NaOH decreased to 75.48% at the ratio of 1:20. In order to 52
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Table 2 Results of the ore reacted with additions of CaO and NaOH at different temperature. Na2SO4/ore mass ratio = 9:20; Additive/ore mass ratio = 0.4:20; Leaching time = 3 h; Liquid-solid ratio = 7.5 mL/g and D90 particle size = 75.225 μm. Additives
Mass of ore/g
Temperature/°C
Mass of residue/ g
Residue ratea
Lithium extraction efficiency
CaO
20.0538 20.0112 20.0287 20.0667 20.0033 20.0718 20.0260 20.0473 20.0256 20.0085
150 170 190 210 230 150 170 190 210 230
20.6018 20.5837 21.9313 23.0548 22.9001 20.8640 21.4458 22.6998 22.5528 22.5919
102.73% 102.86% 109.50% 114.89% 114.48% 103.95% 107.09% 113.23% 112.62% 112.91%
21.31% 29.12% 55.33% 89.52% 90.67% 36.62% 66.98% 85.12% 84.96% 87.34%
NaOH
a
Fig. 6. XRD analysis of leaching residue at NaOH/ore mass ratio of 1:20.
Residue rate is the ratio between the weight of residue and ore mineral.
always 3–8% higher than that for NaOH. It is noticeable that the Li extraction efficiency with NaOH addition peaked at 87.34% at leaching time of 3 h followed with a decreased of around 3% until leaching time of 6 h. This result indicates that further leaching time is not favorable for lithium extraction, 3 h seems to be more suitable.
investigate the reasons for the significant reduction of Li extraction efficiency when the mass ratio of NaOH/ore was over 0.4:20, the leaching residue at the NaOH/ore mass ratio of 1:20 was tested by XRD. As can be seen from the result (Fig. 6), the residue was mainly composed of analcime (NaAlSi2O6·H2O), quartz (Si2O) and virgilite (LixAlxSi3−xO6), which means that the excess NaOH addition led to the loss of Li in residue in the form of virgilite. Thus, in the present result, the additive/ore mass ratio of 0.4:20 seems to favour the lithium extraction. To reduce the addition amount of the additives and achieve the high extraction efficiency for both CaO and NaOH, the mass ratio of 0.4:20 was chosen for the following experiments.
4.1.5. Effect of L/S ratio The effect of different L/S ratio was conducted at 230 °C for 3 h with Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20 and D90 particle size of 75.225 μm. The results are plotted in Fig. 5e. With the L/S ratio increasing from 3 to 7.5 mL/g, it is evident that the Li extraction efficiency for CaO was always 2–6% higher than that for NaOH. When the ratio reached 5 mL/g, the extraction efficiency for CaO addition increased to 89.89% and remained stable at the following ratios (only 90.67% at 7.5 mL/g). Whereas, from 5 mL/g to 7.5 mL/g, the Li extraction efficiency for NaOH addition was still increased obviously and peaked at 87.34% at 7.5 mL/g. Since higher L/S ratio means more energy consumption for concentration in the downstream recovery process, the L/S ratio of 5 mL/g for CaO addition and 7.5 mL/g for NaOH addition seem to be advisable. Nevertheless, it should be concerned that a low L/S ratio (below 5 mL/g) for CaO addition inhibits the mass transfer and leads to solid mixtures sticking on the inner surface of the reactor, making them difficulty to be washed out, because of the swelling of CaO. To facilitate the operation of experiment and make a comparison between two additives under the same conditions, L/S ratio of 7.5 mL/g was chosen for both CaO and NaOH addition.
4.1.3. Effect of leaching temperature The effect of leaching temperature on the Li extraction efficiency was investigated in the range of 150 to 230 °C. The other conditions were as follows: Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20, D90 particle size of 75.225 μm, leaching time of 3 h, L/S ratio of 7.5 mL/g. The results were shown in Fig. 5c, which indicates the temperature had considerable influence on the Li extraction. In the experimented temperature range, the Li extraction efficiency jumped from 21.31 to 90.67% for CaO addition and from 36.62 to 87.34% for NaOH addition. There was no obvious difference between the figure for NaOH and CaO after the temperature reached 190 and 210 °C, respectively. Taking into account the energy consumption, 190 °C for NaOH addition and 210 °C for CaO addition are recommended for the leaching of β-spodumene. However, in order to make a comparison between NaOH and CaO addition under the same conditions and at a high Li extraction efficiency, 230 °C was chosen for the following experiments. In order to clearly investigate the relationship between the weight of residue and Li extraction efficiency, the detailed results of Fig. 5c are presented in Table 2. For showing the increase rate of the weight of residue in comparison to the ore materials, the term of residue rate % (the ratio between the weight of residue and ore material) was introduced in the table. As can be seen, with the leaching temperature increasing, the residue rate had a positive correlation with Li extraction efficiency. At the optimum leaching temperature of 230 °C, the residue rate was 114.48% for CaO addition and 112.91% for NaOH addition, and the Li extraction efficiency reached 90.67% and 87.34%, respectively.
4.1.6. Effect of ore particle size Some experiments with different particle sizes of the ore were conducted to investigate its effect on Li extraction efficiency at 230 °C for 3 h with Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20 and L/S ratio of 7.5 mL/g. The particle diameter at the 90 vol% undersize point in the distribution (D90) was the variable used to describe the particle size (Higgins et al., 2003). The results were plotted in Fig. 5f. When the particle size of ore materials decreased from 164.145 to 39.233 μm, the extraction efficiencies of Li experienced sharp rise. While, when the particle size continues decreasing, the Li extraction efficiency dropped slightly and the gap between the figure for CaO and NaOH narrowed. A reasonable explanation is that the decreasing particle size led to the higher surface energy of particles and hence made them easily form agglomerations (Vieceli et al., 2017; Zhang et al., 2010) that inhibited extraction reaction. Agglomeration phenomenon was extraordinarily obvious at the condition of D90 particle size 8.642 μm, as shown in Fig. 7. Since the Li extraction efficiencies for both CaO and NaOH addition peaked at 39.233 μm, further experiments were conducted using ore materials screened at this size. At this particle size, the extraction efficiencies of Li for CaO and NaOH additives were
4.1.4. Effect of leaching time The effect of leaching time was investigated in the range from 2 to 6 h under the following conditions: Na2SO4/ore mass ratio of 9:20, additive/ore mass ratio of 0.4:20, leaching temperature of 230 °C, D90 particle size of 75.225 μm and L/S ratio of 7.5 mL/g. The results (Fig. 5d) indicate that the leaching time (over 2 h) had relatively slight influence on the extraction efficiency of Li and the figure for CaO was 53
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Fig. 7. SEM images of leaching residue with addition of (a) NaOH and (b) CaO, D90 = 8.642 μm.
Table 3 Compositions (wt%) of the ore and leaching residues. Na2SO4/ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm. Sample
Component (wt%)
Ore Residue from CaO addition Residue from NaOH addition
Li extraction efficiency
Li2O
K2 O
CaO
SiO2
Al2O3
Na2O
MgO
Fe2O3
6.17 0.39 0.53
0.92 0.32 0.28
0.57 1.50 0.21
63.00 54.62 55.42
26.38 21.23 21.85
1.46 11.92 12.24
0.21 0.11 0.082
0.61 0.63 0.50
4.2. Analysis of leaching residue
93.30% and 90.70%, respectively, and the pressure of autoclave was recorded as 2.7 ± 0.1 MPa. Table 3 presents the chemical analysis of leaching residue obtained from the experiment with the highest extraction efficiencies, i.e. 93.30% for CaO addition and 90.70% for NaOH addition. Under the reaction conditions, the mass of leaching residue was around 23.0 g (CaO) or 22.7 g (NaOH). As can be seen from the table, the Li content in residue had decreased from the original value of 6.17% to 0.39 and 0.53% with addition of CaO and NaOH, respectively, and the Na content in residues was risen by over 10% for both additive of CaO and NaOH. According to analyzing, the decreased Li content was equal to the increased Na content in the number of mole. Besides, other components, including K2O, CaO (for NaOH addition), SiO2, Al2O3, MgO and Fe2O3 were also decreased more or less, this might be because the total weight of residue was increased overtaking the weight of ore material as indicated in Table 2.
To confirm the leaching effect with addition of CaO and NaOH, leaching residue obtained from the experiments with the highest extraction efficiencies was tested by SEM (Fig. 8). As shown in Fig. 8a, there are large amount of agglomerations of small particles wrapped around the residue, which may lead to less contact between Na2SO4 solution and ore materials resulting in low extraction efficiency. In contrast, the addition of CaO resulted in the surface of the residue particles being smooth with little agglomeration (Fig. 8b). These observations explain why Li extraction efficiency with NaOH additive was lower than that with CaO additive in some leaching experiments. To investigate the mechanism of the extraction process, the leaching residue was analyzed by XRD. The results (Fig. 9) indicate that the residues with additive of both CaO (Fig. 9a) and NaOH (Fig. 9b) were mainly composed of analcime (NaAlSi2O6·H2O), β-spodumene (βLiAlSi2O6) and quartz (SiO2). Comparing the mineral composition of the reaction materials (Fig. 2), after leaching, the β-spodumene (βLiAlSi2O6) was converted to analcime and the quartz still remained in residue. The result indicates that the extraction process was based on an ion-exchange mechanism, where Li+ in β-spodumene (β- LiAlSi2O6) was replaced by Na+ and leached into solution. The reaction can be represented as:
4.1.7. Reproducibility experiments To confirm the reliability of the leaching result, Three parallel tests were conducted under the following conditions: Na2SO4/additive (CaO or NaOH)/ore mass ratio of 9:0.4:20, leaching temperature of 230 °C, leaching time of 3 h, L/S ratio of 7.5 mL/g and D90 particle size of 39.233 μm. The results are shown in Table 4. The standard deviation with the addition of CaO (0.49%) and NaOH (0.57%) were less than 2%, which indicated that the results are reproducible under the evaluated conditions. The Li extraction efficiency of three parallel tests are not significantly different. This is favorable for further researching the optimum process in our future work.
OH−
2β − LiAlSi2 O6 (s) + Na2SO4 (s) + 2H2 O (l) ⎯⎯⎯⎯⎯→ 2NaAlSi2 O6 ·H2 O (s) + Li2 SO4 (aq)
CaO NaOH
Li extraction efficiency (%) from parallel experiments 1#
2#
3#
92.73 91.10
93.92 90.50
93.18 89.70
Average (%)
Standard deviation (%)
93.28 90.43
0.49 0.57
(3)
From Eq. (3), the weight of solid residue is predicted to be greater than the ore materials, which can account for the residue rate being over 100% and the positive correlation between Li extraction efficiency and residue rate (indicated in Table 2). The ion-exchange based mechanism is similar to that previously reported for methods using sulfuric acid (Xiao et al., 1997) and calcium chloride roasting (Barbosa et al., 2015) to extract lithium from β-spodumene, where Li+ was replaced by H+ and Ca2+, respectively. However, this extraction process was built on strong base transforming to weak base in the alkaline atmosphere. The product analcime can be applied in environmental protection, catalyst preparation and ceramic production, which has been widely researched before. Such as, modified Ni (II) loaded analcime electrode was used to catalyze the electrooxidation of methanol (Azizi et al.,
Table 4 Results of parallel experiments under the conditions of Na2SO4/additive (CaO or NaOH)/ ore mass ratio 9:0.4:20, leaching temperature 230 °C, leaching time 3 h, L/S ratio 7.5 mL/ g and D90 particle size 39.233 μm. Additives
– 93.30% 90.70%
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Fig. 8. SEM images of leaching residue with additive of (a) NaOH and (b) CaO. Na2SO4/ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/ g and D90 particle size = 39.233 μm.
Table 5 Chemical composition of the leaching solution. Na2SO4/ore mass ratio = 9:20, Additive/ ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm. The volume of liquor was 1 L, mass of ore was 40 g. Leaching solution
Solution from CaO addition Solution from NaOH addition
The concentration of components (mg/L) Li2O
Na2O
CaO
SiO2
Al2O3
K2O
MgO
Fe2O3
2293
1860
54.88
126
0.064
91.62
0.15
0.0034
2250
2359
3.28
223
0.038
124.13
0.20
0.0170
Fig. 10. Firstly, β-spodumene is leached in an autoclave with Na2SO4 and associated CaO or NaOH additive. Through filtration, Li+ will remain in solution and Na+ will report to the residue. The filter liquor and washing water were diluted with few distilled water to 1 L together. Table 5 lists the chemical composition of the leaching solution obtained from the experiment with the highest extraction efficiencies. Relatively few impurities in the leaching solution contributed to simplify the purification process, which was a comparatively mature process in the lithium industry (Vieceli et al., 2018; Sitando and Crouse, 2012; Swain, 2017). Some impurities were removed by pH control with lime in leaching liquor, whereafter, redundant Ca2+ was cleaned by adding moderate Na2CO3. After purification and concentration, Li contained in solution could be easily recovered by adding Na2CO3 to form Li2CO3 precipitate according to Eq. (2) (Meshram et al., 2014). This method for precipitating Li has been well studied and is very common in most industrial cases (Meshram et al., 2014; Swain, 2017; Wilkomirsky, 1999; Zhang et al., 1998). Finally, the mother solution mainly containing Na2SO4 obtained after precipitation of Li can be reused to commence the next cycle of autoclave leaching to achieve a closed-loop. Compared with the previously reported methods (Table 1), the suggested process is largely simplified, just involves common chemicals, and the leaching residue can be the reused resource for glass ceramic industry and environmental protection field, which make it cost-effective, eco-friendly and straightforward.
Fig. 9. XRD analysis of leaching residue with additive of (a) NaOH and (b) CaO. Na2SO4/ ore mass ratio = 9:20, Additive/ore mass ratio = 0.4:20, T = 230 °C, t = 3 h, L/S ratio = 7.5 mL/g and D90 particle size = 39.233 μm.
2014), modified zincon loaded analcime to sorb preconcentration of palladium (Taher et al., 2007), the contained F−, NH4+ and Cd2+ in the waste water were separated by synthesis analcime as absorbent or ion-exchange material (Chen, 2015; Yuan et al., 2016; Gu et al., 2008; Wang et al., 2003), and the analcime-bearing ore was as a raw for ceramic industry (Shushkov et al., 2011). So the leaching residue could be recycled for another stage not to be abandoned, under these potential applications the process may be an optionally environment friendly course for extracting Li from β-spodumene. 4.3. A suggested closed-loop process for the extraction and recovery of Li from β-spodumene Based on the preceding results, a closed-loop process for extracting and recovering Li from β-spodumene can be proposed as outlined in
Fig. 10. Flow chart of the suggested closed-loop process for the extraction and recovery of Li from spodumene.
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5. Conclusions
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A closed-loop process of extracting and recovery Li from β-spodumene by leaching with Na2SO4 in pressure leaching was proposed. The effects of two kinds of additive (CaO and NaOH) on the extraction efficiency of Li were investigated and compared. Over 90% Li was attained with this process. The highest Li extraction efficiencies, i.e. 93.30% for CaO addition and 90.70% for NaOH, were observed under the following conditions: Na2SO4/additive (CaO or NaOH)/ore mass ratio of 9:0.4:20, leaching temperature of 230 °C, leaching time of 3 h, L/S ratio of 7.5 mL/g and particle size (D90) of 39.233 μm. It was found that significant amount of agglomerations were generated around ore particles when adding NaOH, which may account for its lower extraction efficiency in comparison to adding CaO. By analysis of leaching residue, the extraction reaction was found to be based on ion-exchange between Li+ and Na+, with β-spodumene (β-LiAlSi2O6) converted into analcime (NaAlSi2O6·H2O). Finally, a closed-loop process based on the results of this study for the extraction of Li from β-spodumene was proposed. This work provided an environmentally friendly, possibly cost-effective and comparatively straightforward way to extract lithium from β-spodumene, which has the potential to be industrially developed. Acknowledgements The authors thank the financial support from the National Key Technology R&D Program of China during the 12th Five-year Plan Period (Grant No.2012BAB10B02). References Azizi, S.N., Ghasemi, S., Gilani, N.S., 2014. An electrode with Ni(II) loaded analcime zeolite catalyst for the electrooxidation of methanol. Chin. J. Catal. 35 (3), 383–390. Barbosa, L.I., Valente, N.G., Gonzalez, J.A., 2013. Kinetic study on the chlorination of βspodumene for lithium extraction with Cl2 gas. Thermochim. Acta 557, 61–67. Barbosa, L.I., González, J.A., Ruiz, M.d.C., 2015. Extraction of lithium from β-spodumene using chlorination roasting with calcium chloride. Thermochim. Acta 605, 63–67. Botto, I.L., 1985. Structural and spectroscopic properties of leached spodumene in the acid roast processing. Mater. Chem. Phys. 13 (5), 423–436. Brumbaugh, R.J., Fanus, W.E., 1954. Determination of lithium in spodumene by flame photometry. Anal. Chem. 26 (3), 463–465. Chen, F., 2015. Treatment of fluorine water by porous analcite balls. Conserv. Util. Miner. Resour. 2, 45–49 (In Chinese). Chen, Y., Tian, Q., Chen, B., Shi, X., Liao, T., 2011. Preparation of lithium carbonate from spodumene by a sodium carbonate autoclave process. Hydrometallurgy 109 (1–2), 43–46. Ellestad, R.B. and Leute, K.M., 1950. Method of extracting lithium values from spodumene ores, US Patent 2516109. Friedman-Rudovsky, J., 2011. Dreams of a lithium empire. Science 334 (6058), 896–897. Grosjean, C., Miranda, P.H., Perrin, M., Poggi, P., 2012. Assessment of world lithium resources and consequences of their geographic distribution on the expected development of the electric vehicle industry. Renew. Sust. Energ. Rev. 16 (3), 1735–1744. Gu, B., Shang, Y., Wu, J., Meng, C., 2008. Ion exchange of Cd2+ synthesized analcime. Ion Exchange Adsorpt. 2, 154–162 (In Chinese). Higgins, J.P., et al., 2003. Spectroscopic approach for on-line monitoring of particle size during the processing of pharmaceutical nanoparticles. Anal. Chem. 75 (8), 1777–1785. Jandová, J., Dvořák, P., Vu, H.N., 2010. Processing of zinnwaldite waste to obtain Li2CO3. Hydrometallurgy 103 (1–4), 12–18. Jaskula, B.W., 2013. Lithium, Minerals Yearbook-2012, USGS. Available at. http:// minerals.usgs.gov/minerals/pubs/commodity/lithium/myb1-2012-lithi.pdf,
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