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desorption properties of lithium ion-sieves in aqueous solution and recovery of lithium from borogypsum
Journal of Environmental Chemical Engineering 3 (2015) 2670–2683
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Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece
Li+ adsorption/desorption properties of lithium ion-sieves in aqueous solution and recovery of lithium from borogypsum anb Ferda Özmala,* , Yunus Erdog a b
Department of Biochemistry, Dumlupınar University, Kütahya 43100, Turkey Department of Chemistry, Dumlupınar University, Kütahya 43100, Turkey
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 July 2015 Received in revised form 18 September 2015 Accepted 28 September 2015 Available online 9 October 2015
This study presents the recovery of lithium from borogypsum by lithium ion-sieves known as selective adsorbents. In the study two types of ion-sieves were used. One was l-MnO2 which was obtained by the treatment of LiMn2O4 with acid and the other was prepared via the acid treatment of LiNi0.5Mn1.5O4 which occurred by the substitution some of manganese with nickel. Besides the lithium adsorption and desorption capacities, manganese and nickel dissolution ratios from the spinel powders were also studied. Optimum adsorption and desorption conditions were determined in the LiOH and HCl solutions. XRD and SEM analyses showed that substitution of manganese with nickel and treatment of spinel powders with acid did not destroy the spinel structure and morphology. Because of the cell-contraction, nickel-substituted spinel did not show any satisfying Li+ extraction and adsorption properties. ã 2015 Elsevier Ltd. All rights reserved.
Keywords: Borogypsum Lithium Ion-sieve Adsorption Desorption yield Manganese dissolution ratio
1. Introduction In recent years lithium has a great importance because of its strategic value in different usage areas. It is mainly used for electrical vehicles, aircrafts as a light alloy when mixed with Al, rechargeable batteries for mobile devices and nuclear fusions [1–3]. According to the 6Li + n ! 3T + 4He reaction, being an alternative energy fuel of future has increased the interest on lithium. Its main reserves are spodumene, petallite, lepidolite, amblygonite minerals and brines. However, these reserves are not sufficient to overcome the demand for lithium in the near future. Seawater is considered as a vast source of lithium by many researchers and many studies have been performed although its concentration in seawater is very low (0.17 mg/L) [3–7]. In Turkey, lithium is mostly found in the clay minerals in borate deposits and in the salt lakes. Investigations have shown that both the waters of Tuzgölü Lake and the clays associated with boron minerals are the potential lithium resources inTurkey [8]. According to our previous studies, industrial boron wastes contain at least 300–600 mg/kg Li+[8,9]. In addition to these reserves, industrial boron wastes are very important potential for lithium production. Recovering lithium from a source that is classified as a waste is so economical and contributes at solving an environmental problem.
* Corresponding author: Fax: +90 2742652056. E-mail addresses: [email protected] (F. Özmal), an). [email protected] (Y. Erdog http://dx.doi.org/10.1016/j.jece.2015.09.024 2213-3437/ ã 2015 Elsevier Ltd. All rights reserved.
Borogypsum is a by-product in the production process of boric acid. According to the following reaction: 2CaO.3B2O3.5H2O + 2H2SO4 + 6H2O ! 6H3BO3 + 2CaSO4.2H2O
(1)
to produce a tonne of boric acid, 1.5 tones of colemanite is fed in to the process and 0.5 tonne of borogypsum is produced as waste. The boric acid production rate of Emet Boron Process Management of Turkey is known as 240,000 tones a year and the waste amount is about 120,000 tones. Utilizing this waste by recovering the valuable metals such as lithium may be very economical because the amount of lithium in this source is nearly 1500 times greater than the amount in seawater. To recover the lithium from borogypsum, spinel type manganese oxides were used in the study. These oxides were preferred because of their high affinity to the Li+ only, high stability, low toxicity and low cost [3,6,10]. By the treatment of LiMn2O4 with an acid solution a new structure referred as l-MnO2 can be obtained. In this new structure all the lithium at the tetrahedral sites goes out and an ion-sieve, l-MnO2, occurs. This structure can take the Li+ back from the solution among the other ions selectively [6]. There is a restriction in the usage of LiMn2O4 due to the Mn dissolution. During the Li+ extraction by acid treatment Mn3+ disproportionate to Mn2+ and Mn4+ according to the following reaction: 2Mn3+ ! Mn2+ + Mn4+
(2)
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Mn4+ remains in the structure and keeps the structure from being destroyed during the formation of l-MnO2 while the Mn2+ effects the structure negatively by dissolving [6]. As the Mn is dissolved at each usage, the spinel structure looses its property being an ion-sieve. Several methods have been considered to overcome this problem. One of them is the synthesis of the spinel structures including tetravalent manganese only. These kind of manganese oxides are known as having high lithium adsorption capacity and low manganese dissolution ratio but the process for synthesizing these materials is quite difficult [11,12]. Cation substitution is another way for solving the problem. By this method average valence of manganese increases and the spinel structure comes closer to the structures containing Mn4+ only. It is also possible to decrease the Mn dissolution ratio [13,14]. In this study LiMn2O4 and a cation substituted spinel, LiNi0.5Mn1.5O4, are studied. Their structures, stability and morphologies were investigated before and after acid treatment. Mn and Ni dissolution ratios after acid treatment, Li+ adsorption properties from LiOH solution, borogypsum solution and desorption yields were also investigated and the results of both spinels were compared to each other.
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2.3. Characterization The chemical analyses of borogypsum was performed by (Rigaku ZSX Primus) XRF and (Varian AA240FS) AAS. The crystalline phases of the powders before and after acid treatment were determined by X-ray analysis (Rigaku-miniflex) at a speed of 2 /min and 0.01 steps, by using CuKa radiation between 2 and 70 . To investigate the differences between the morphologies of the powders and the ion-sieves, a scanning electron microscope (SEM) (Zeiss Supra 50 VP) was used. 2.4. Li+ adsorption / desorption process from solution by batchwise
2. Experimental
A constant mass of l-MnO2 and the ion-sieve SN were immerged in 25 ml of LiOH solution at 22 C for 2 h. The lithium ion concentration was 200 mg/L. pH varied from 4 to 12.40 which is the original pH value of LiOH solutions at the studied concentration. The ion-sieves were separated from the solutions by filtration with membrane filters with pore size of 200 nm (Schleicher & SchuellNL 16) after attainment of the equilibrium and the equilibrium lithium concentrations in the solution were determined by ICPOES. The lithium adsorption capacities of these ion-sieves were calculated using the following equation.
2.1. Materials
Qe ¼
LiMn2O4 and LiNi0.5Mn1.5O4 spinel powders (more than 99%) were obtained from Sigma-Aldrich with pore size less than 0.5 mm. Borogypsum, the waste from Emet Boric Acid Plant, was used as a lithium source. It was obtained from the waste pool of the plant in mud form.
where Qe is the lithium adsorption capacity; C0 and Ce are the initial and equilibrium Li+ concentrations in the solution, respectively; V is the solution volume and m is the weight of the dry ion-sieves. The optimum adsorption time, temperature, initial concentration and adsorbent dosage were also studied to obtain the maximum recovery of lithium. Desorption of lithium from ion-sieves is achieved with 0.1 M HCl. Constant mass of LiMn2O4 and LiNi0.5Mn1.5O4 (by the insertion of lithium into ion-sieves, ion-sieves turn to their initial form) was immerged in HCl solution. All the other conditions in the desorption process are same as the ones in adsorption process. After the desorption process is completed lithium concentrations were determined in the acid solutions. The optimum adsorption and desorption conditions were decided with LiOH and HCl solutions, then these conditions were adapted to the experiments performed with borogypsum.
2.2. Preparation of ion-sieves and borogypsum 0.1 g of both LiMn2O4 and LiNi0.5Mn1.5O4 spinel powder were immerged in 25 ml of HCl and HNO3 solutions at different concentrations (0.1–0.5 M) at 25 C for 24 h. The lithium and manganese concentrations of both spinels and nickel concentrations for LiNi0.5Mn1.5O4 were determined in the filtrate solutions after acid treatment. Lithium, manganese and nickel concentrations were detected by an inductively coupled plasma spectrometer (ICP) (PerkinElmer, 4300 DV). These metals dissolution ratios (Rdis.) from the spinel powders were calculated using the following Eq. (3). Rdis ¼
mfiltrate mtheorical
C0 Ce m
ð4Þ
2.5. Equilibrium isotherm ð3Þ
where mfiltrate is the mass of metallic elements in the filtrate solution after acid treatment in the unit of mg/L, mtheorical is the total metal mass in the studied amount of spinel powder at constant solution volume. LiMn2O4 and LiNi0.5Mn1.5O4 spinels were turned to lithium ionsieves after acid treatment. They were designated as l-MnO2 and the ion-sieve SN, respectively. Acid treatment experiments showed that using 0.1 M HCl solution is most suitable for delithiating the spinel powders. A stock mass of ion- sieves were prepared for both spinels using 10 g of powder and 2.5 L of HCl for 24 h. Then the acid-treated materials were filtered with pore 4, washed with deionized water and dried at 100 C overnight to obtain the final ion-sieves. Borogypsum was dried at 110 C for 48 h. After that it was grinded to the pore size of 63 mm and the experiments were performed to decide the optimum dissolution conditions of borogypsum.
A constant mass (0.1 g) of l-MnO2 and ion-sieve SN were immerged in a series of LiOH solutions (25 ml) at room temperature for 20 mins. The pH of the solutions was fixed to 12.40 while the lithium concentrations were changed between 10 and 200 mg/L. The Langmuir isotherm equation was used to characterize the uptake properties of the ion-sieves. The isothermal equation is expressed as: Ce 1 1 ¼ Ce þ KLQ m Qe Qm
ð5Þ
where Ce is the equilibrium Li+ concentration of the solution, Qe is the equilibrium Li+ adsorption capacity, Qm is the theoretical maximum adsorption capacity and the KL is the Langmuir empirical constant. The values of Qm and KL can be calculated from the slope and intercept of plot of Ce/Qe vs. Ce. 2.6. Adsorption/ desorption of lithium from borogypsum 10 g of borogypsum which was calcined at 600 C for 60 min was immerged in 50 ml of 0.1 M HCl solution and refluxed for 2 h.
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Table 1 XRF results for the borogypsum.
Table 2 AAS results for the trace elements in borogypsum.
Components
% (W)
Detection limit
Components
mg/kg
Na2O MgO Al2O3 SiO2 P2O5 SO3 Cl F K2O CaO TiO2 MnO Fe2O3 ZnO As2O3 SrO B2O3a Ignition loss
0.0469 1.89 1.15 7.36 0.0280 37.5 0.0421 0.224 0.679 27.7 0.0789 0.0109 0.609 0.0048 0.400 1.17 2.13 19.20
0.0070 0.0074 0.0027 0.0041 0.0014 0.0060 0.0021 0.0718 0.0013 0.0042 0.0069 0.0029 0.0023 0.0012 0.0013 0.0009 – –
Li Rb Cs Cr Co Cu Y Cd Ba La Ce Pb Ni Th
295 5 90 2 116 3 3.0 0.6 <0.27 <0.13 1.0 0.5 <0.05 90 9 1.5 0.7 6.0 1.1 8.0 1.9 <0.30 <2.4
a
B2O3 analysis was performed at Emet boric acid plant by volumetric method.
The solution was filtered and Li, Mn and Ca analyses were performed in the filtrate solution. Then Na2CO3 was added to the solution and CaCO3 was filtered and removed from the solution while the lithium and manganese concentrations did not change. After that the solution was diluted at the 1/2 ratio. By this way, it became possible to study at the concentration at which the adsorption and desorption yields are very high (20 ppm). The solution pH was adjusted to 12.40 and as increasing the pH, there became an intensive precipitation in the solution. After the last filtration process, the solution was ready to use in the adsorption experiments. Before the solution was added on the ion-sieves lithium, manganese and nickel concentrations in the solution was detected again and it was seen that all the manganese in the
solution was precipitated while the lithium concentration was still constant. Because of the negative effect of the magnesium on the lithium adsorption from the solutions, the magnesium amount in the solution was also controlled and it was found that there was no magnesium in the solution. Then, 0.1 g ion-sieve was immerged in 25 ml of the prepared solution. It was mixed at 500 rev/min for 20 min at room temperature and filtred by membrane filters. The ion sieves which adsorbed lithium in their structure were dried on filters overnight and delithiated with 0.1 M HCl. 3. Results and discussion 3.1. Chemical analyses of borogypsum Table 1 shows XRF analysis of major elements in borogypsum and Table 2 shows the trace elements concentrations in the sample by AAS.
Fig. 1. XRD patterns of LiMn2O4 and LiNi0.5Mn1.5O4.
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Fig. 2. XRD patterns of LiMn2O4 before and after acid treatment.
3.2. Stability of LiMn2O4 and LiNi0.5Mn1.5O4 3.2.1. Structural analyses of LiMn2O4 and LiNi0.5Mn1.5O4 Fig. 1 shows the XRD patterns of LiMn2O4 and LiNi0.5Mn1.5O4. Ni in the spinel structure does not destroy the structure of the powder. XRD diffraction peaks of LiNi0.5Mn1.5O4 move to the higher angle direction according to the peaks of LiMn2O4. This result is attributed to cell contraction. Replacement of Mn3+ by Ni2+ creates a shrinkage at the lattice. By the substitution of Mn3+ with
Ni2+, some Mn3+ are oxidized to Mn4+ to keep the charge balance as Ni2+ has the lower valance than Mn3+. Ionic radius of Mn4+ is 0054 nm while the Mn3+ has an ionic radius of 0,0645 nm [15]. 3.2.2. Structure and morphology of LiMn2O4 and LiNi0.5Mn1.5O4 before and after acid treatment Fig. 2 shows the XRD patterns of LiMn2O4 before and after the acid treatment. By the acid treatment of LiMn2O4, Li+ extracts from
Fig. 3. XRD patterns of LiNi0.5Mn1.5O4 before and after acid treatment.
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Fig. 4. SEM images of LiMn2O4 (a) before and (b) after the acid treatment.
the structure and a spinel-type manganese oxide defined as l-MnO2 is prepared [16]. After the acid treatment, there is no change at the XRD patterns only the difference can be released as the shifting to the higher angle direction. This means that during the acid treatment, LiMn2O4 maintains its main structure but there becomes a cell contraction due to the Li+ extraction by the redox reaction [16]. Diffraction peaks of LiNi0.5Mn1.5O4 also indicate shifting to higher angle direction after acid treatment (Fig. 3). By substituting some of the manganese with Ni, the structure increases its Mn4+ content in order to keep its average valence as a result of which this spinel shows ion-exchange properties in Li+ extraction and insertion [17]. The differences between the ionic radii of Li+ (78 pm) and H+ (1,2 pm) are the reason of cell contraction. Figures 4 and 5 show the morphologies of LiMn2O4 and LiNi0.5Mn1.5O4 before and after the acid treatment, respectively. Both of the spinels, LiMn2O4 and LiNi0.5Mn1.5O4, have even and fine particles before acid treatment but it is possible to say that the particles of LiNi0.5Mn1.5O4 are thinner than the particles of LiMn2O4. The particle size of both of the spinels are less than 200 nm. After the acid treatment, we can say that the morphologies of the spinels are still the same as the ones before the acid treatment. The acid treatment has a little effect on increasing grain size and agglomeration [7]. Agglomeration is more
effective at the spinel with nickel because its particle size is less than the other. It is possible to say there is no change in the morphologies of the spinels by the acid treatment. 3.2.3. Mn dissolution of LiMn2O4 and LiNi0.5Mn1.5O4 2 Mn3+ ! Mn2+ + Mn4+ according to the disproportion reaction Mn4+ remains in the structure to form l-MnO2 and the Mn2+ is the manganese that is responsible from the dissolution in the acid solutions. When Mn3+ substitutes with nickel, the amount of Mn3+ that turns to Mn2+ reduces. That is the reason why LiNi0.5Mn1.5O4 is more stable in acid solutions than LiMn2O4. Figs. 6 and 7 show the metallic dissolution ratios (Mn, Ni) of spinel powders with different acid solutions. For both of the powders studying with 0.1 M HCl is more suitable. At this concentration the ion-sieves show the lowest dissolution ratios. 3.3. Li+ adsorption of LiMn2O4 and LiNi0.5Mn1.5O4 from synthetic solution and desorption process 3.3.1. Effect of pH Lithium adsorption capacities of ion-sieves by batch tests from LiOH solution at different pH values were studied. The pH values of solution was changed from 4 to 12.40 which is the original pH value
Fig. 5. SEM images of LiNi0.5Mn1.5O4 (a) before and (b) after the acid treatment.
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Fig. 6. Mn dissolution ratios from LiMn2O4 with different acids and concentration.
of the solution at the studied concentration. The results are shown in Fig. 8. There is a gentle increase of adsorption capacity (q) between the pH 4–10 while the increase after pH 10 is quite rapid. The adsorption capacity reaches the maximum of 34.70 and 8.93 mg/g for l-MnO2 and ion-sieve SN, respectively. Desorption yield of the lithium from the l-MnO2 that is adsorbed at the higher pH values is also higher than the yield adsorbed at lower pH values. However, for the ion-sieve SN, there is a decrease after pH 10 (Fig. 9). Mn dissolution that occurs during the desorption of Li which is adsorbed on l-MnO2 at pH 12.40 is 10.42%. This value decreases with the decreasing pH (Table 3). At the lower pH values, the lithium adsorption capacity is also very small. (&) [MnIV2]O4 + n LiOH ! (Lin&1n) [Mn(III)nMn(IV)2-n] O4 + (n/2) H2O + (n/4) O2 (6)
In the reaction (6) the symbols (), [], & are 8a tetrahedralsites, 16 d octahedral sites and vacant sites, respectively [16]. According to the reaction, as the amount of lithium that is adsorbed on the l-MnO2 decreases, the amount of the Mn(III) in the LiMn2O4 also decreases. It is known that Mn dissolution from LiMn2O4 (LiMn3 + Mn4+O4) in acid solution proceeds as a disproportion: 2Mn3+ ! Mn2+ + Mn4+. The Mn4+ remains in the spinel skeleton to form l-MnO2 and Mn2+ dissolves in acid solution [6]. Due to the Ni2+ substituting of Mn3+, Mn4+ content of the spinel structure (LiNi0.5Mn1.5O4) becomes higher. So, lithium extraction process of the spinel can be attributed to Li+ H+ ion – exchange reaction substantially. By this way, the amount of Mn2+ which occurs by the disproportion reaction of Mn3+ is quite less. As the pH increases, the amount of Mn and Ni that extracted from the structure decrease (Table 3). The low lithium adsorption capacity
Fig. 7. Mn and Ni dissolution ratios from LiNi0.5Mn1.5O4 with different acids and concentrations.
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Fig. 8. Lithium adsorption capacities of ion-sieves from the solutions at different pH values (T = 22 C, ion-sieve mass = 0.1 g, CLi+ = 200 mg/L, V = 25 ml, t = 2 h).
of ion-sieve SN at low pH values can be explained by destroying of structure partly by dissolving of Mn and Ni from the sieve too much at low pH values. 3.3.2. Time dependence of the study Effect of time at the Li+ adsorption and desorption of ion-sieves at pH 12.40 and changing at the dissolution ratios of metallic elements from the ion-sieves by time were investigated. Fig. 10 illustrates the evolution at the uptake data of Li+ as function of time for both l-MnO2 and ion-sieve SN. It appears from Fig. 10 that experiment curves show a rapid initial rise of adsorption capacities (q). The maximum amount of uptake (91%) is achieved within 20 mins for l-MnO2 which is faster than Li+ uptake by other
ion-sieves from different Li+ solutions and seawater [3,4]. The reason could be ascribed to the higher Li+ concentration (200 mg/L) and being no cations for competition in the media. Also the purity of spinel powders are more than 99% and they are nano-sized powders and for LiMn2O4, the maximum desorption yield (90.36%) is also achieved within 20 mins (Fig. 11). This result is quite important when the cycle rate of a process is considered. Mn dissolution rate of LiMn2O4 increases with the time and reaches to value of 10.92% after 120 mins. To reach the maximum Li+ uptake in 20 mins is also very important for the manganese dissolution rate being less at this time period. Alltheexperimentsperformedfor l-MnO2 werereapeatedforionsieve SN. The results are closed with the results of l-MnO2.
Fig. 9. Desorption yield of the lithium that is adsorbed at different pH values by lithium ion-sieves. (CH+ = 0.1 mol/L)
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Table 3 Mn and Ni dissolution ratios of ion-sieves during the desorption process at pH study. pH
4 6 8 10 12.40
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
1.94 2.37 2.57 2.58 10.42
1.62 1.59 1.54 1.48 1.40
3.16 3.07 2.92 2.91 2.67
Adsorption reaches the equilibrium within the 20 mins. Also it is possible to reach the maximum desorption yield (67.76%) at the same period(Fig.11).Asthecontacttime of theacidincreases,the MnandNi dissolutionratiosoftheion-sivesalsoincrease(Table4).Theion-sieve having the maximum Li+ adsorption capacity at the time at which the metallic element dissolution rate is fewer is a great advantage for the ion-sieveinordertoincreasethelifetimeofthesieve.Itisknownthatas the metallic elements dissolve from the structure, the spinel powders lose their property of being an ion-sieve. 3.3.3. Effect of temperature Experiments were performed at different temperatures; 22, 30, 40, 50, 60 C. From the slopes in Fig. 12, we can see the increase at the Li+ adsorption capacity with the increasing of temperature. The results show the endothermic nature of the sorption. These spinel manganese oxide ion-sieves have plenty of pores and cavities; especially the cavities in tetrahedral 8a sites only permit the small ions to pass in and out, e.g., Li+ and H+[1]. Li+ sorption or insertion activity requires a diffusion process, which is an endothermic process. Increasing of the temperature supports the adsorbate transport within the pores of the adsorbent. On the other hand, for the exchange of Li+ and H+, firstly extraction of proton from the structure must be occurred. This is possible with the breaking of the bond between OH. The bond breaking is also an endothermic process [1]. Ion-exchange reaction can be written as (where S represents the main body of the sieve) RSOH+ Li+ $ RSOLi+ H+
(7)
Desorption yield increases with the increasing temperature for both of the ion-sieves (Fig. 13). Also, from the Table 5 it can be
clearly seen that at the desorption process at constant experimental period as the temperature increases Mn and Ni dissolution ratios of the sieves increase, correspondingly. Especially dissolution of manganese from l-MnO2 changes substantially from 7.30 to 11.44 while the increase at the ion-sieve SN is so smooth, 1.32– 1.70. The reason of manganese dissolution rate of ion-sieve SN being less than the l-MnO2 is due to the nickel creating cell contraction at the structure. But the dissolution of nickel with the increasing temperature from this sieve cannot be ignored. Its nickel dissolution ratios changes from 1.82 to 4.91%. As the temperature increases, the amount of lithium that is adsorbed and desorbed also increases. But this increase is not very significant as the values are close to each other. When the negative effect of temperature increase on the manganese and nickel dissolution is considered, studying at the room temperature is preferred. 3.3.4. Effect of initial concentration A rising trend of adsorption capacity can be seen with the increasing initial Li+ concentration in Fig. 14. For l-MnO2, this increase is quite significant while the increase for ion-sieve SN is changing slightly. For both of the ion-sieves, the sorption process is governed by two steps which are boundary layer diffusion and intraparticle diffusion. By increasing the initial concentration of lithium, the surface of the ion-sieve is contacted with more lithium, which resulted by the diffusion of the Li+ at a larger amount through the boundary layer in unit time. The boundary layer diffusion is more important in Li+ uptake by l-MnO2 as the intraparticle diffusion has the greatest effect in the ion-sieve SN [1,18].
Fig. 10. Lithium adsorption capacities of ion-sieves at different contact times (T = 22 C; ion-sieve mass = 0.1 g; pH 12.40; CLi+ = 200 mg/L; V = 25 ml).
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Fig. 11. Desorption yield of the lithium at different contact times by lithium ion-sieves.
Table 4 Mn and Ni dissolution ratios of ion-sieves during the desorption process at time dependency study. Time (min)
5 10 15 20 30 40 60 80 100 120
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
6.27 6.25 8.02 8.10 8.47 9.21 9.95 9.76 10.99 10.92
1.27 1.42 1.49 1.44 1.59 1.61 1.59 1.62 1.67 1.61
1.44 2.04 2.19 2.35 2.78 3.24 3.00 3.14 3.11 3.23
Fig. 12. Lithium adsorption capacities of ion-sieves at different temperatures (ion-sieve mass = 0.1 g; pH 12.40; t = 20 min., CLi+ = 200 mg/L; V = 25 ml).
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Fig. 13. Desorption yield of the lithium at different temperatures by lithium ion-sieves.
Table 5 Mn and Ni dissolution ratios of ion-sieves during the desorption process at temperature study. Temperature ( C)
22 30 40 50 60
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
7.30 8.92 11.10 11.40 11.44
1.32 1.40 1.50 1.59 1.70
1.82 2.09 3.02 3.33 4.91
Fig. 14. Lithium adsorption capacities of ion-sieves at different initial concentrations (ion-sieve mass = 0.1 g; pH 12.40; t = 20 min., T = 22 C; V = 25 ml).
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Fig. 15. Desorption yield of lithium at different initial concentrations by lithium ion-sieves.
Table 6 Mn and Ni dissolution ratios of ion-sieves during the desorption process at different initial concentrations. Initial concentration (mg/L)
10 20 40 100 150 200
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%
Ni dissolution ratio (%)
5.97 6.12 6.54 7.89 8.02 8.15
0.72 0.80 0.89 1.19 1.27 1.36
2.51 2.52 2.50 2.48 2.52 2.49
Fig. 16. Lithium adsorption capacities of ion-sieves at different adsorbent dosages (pH 12.40; t = 20 min., T = 22 C; C0 = 1000 mg/L; V = 25 ml).
an / Journal of Environmental Chemical Engineering 3 (2015) 2670–2683 F. Özmal, Y. Erdog Table 7 Langmuir isotherm model parameters for the adsorption of Li+ onto ion-sieves. Ion-sieve
qmax (mg g1)
r2
KL (L mg1)
l-MnO2
35.71 10.87
0.998 0.973
0.144 0.016
Ion-sieve S–N
Desorption yield of Li+ that is adsorbed by l-MnO2 decreased by increasing initial concentration. The reason can be ascribed to the studied constant concentration and volume of the acid used for desorption as the amount of lithium that is adsorbed by l-MnO2 changed by different initial concentrations. As shown in Fig. 15 desorption yield of the ion-sieve with nickel did not show a significant change by the initial concentration. Dissolution rate of manganese for both of the ion-sieves has increased with the increasing initial concentration. Reaction (6) describes the reason of rising. As the amount of Li+ that is adsorbed increases, the amount of Mn(III) also increases. After that, Mn(III) disproportionates to Mn4+ and Mn2+. Mn2+ is the form of manganese which is responsible from the manganese dissolution. The increase of the dissolution rate of manganese is lesser for the ion-sieve SN due to Li+ insertion and extraction reactions from the structure is considered to be the ion-exchange mostly. The dissolution rate of nickel is said to be nearly constant for this ionsieve (Table 6). The Li+ adsorption data of the ion-sieves as a function of equilibrium concentrations at 22 C were fitted to the Langmuir isotherm equation for both of the sieves (Table 7). The correlation coefficients (R2) of l-MnO2 and ion-sieve SN were calculated as 0.998 and 0.973, respectively. The isotherm coefficients Qm and KL can be obtained from the slope and the intercept of the linear plots. For l-MnO2, these values are 35.71 mg/g and 0.144 L/mg; for the ion-sieve SN the values are 10.87 mg/g ve 0.016 L/mg, respectively. The obtained values for l-MnO2 is greater than the values for ion-sieve with nickel. The reason is attributed to the l-MnO2’s higher performance at Li+ adsorption from the solution. 3.3.5. The effect of ion-sieve dose on recovery of lithium It is known that the adsorbent dose has a great influence in adsorption process because the number of binding sites in this
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process was indicated by the dose of the adsorbent added into the solution. At the same time, it also indicates the number of Li+ insertion sites [19,20]. The results are shown at Fig. 16. As the dose of adsorbent increases from 0.1 to 0.5 g, the amount of adsorbed Li+ decreases. The reason can be attributed to the unsaturation of adsorption sites and particle interaction. As seen clearly from Fig. 17 desorption yield increases by the increasing adsorbent dosage because absorbent surface area of the adsorbent increases with increasing dosage. For both ion-sieves, increasing the dose after 0.4 g does not create a significant change at the amount of the Li+ adsorbed. This means that the equilibrium is established between the adsorbent and Li+ at this dosage. At l-MnO2 by the increasing dose the amount of Mn3+ and Mn2+ decreases because the amount of lithium that is adsorbed also decreases. At the ion-sieve SN, ion-exchange reaction is most effective than redox reaction so as the amount of lithium that is adsorbed decreases by the increasing dose, the amount of Li+ that exchanges with the H+ decreases, too. This is the reason for the slight decrease of Mn2+ and Ni+ dissolution with increasing adsorbent dosage (Table 8). 3.4. Li+ adsorption of LiMn2O4 and LiNi0.5Mn1.5O4 from borogypsum solution and desorption process To determine the maximum lithium adsorption capacity and desorption yield of ion-sieves, optimum conditions at the adsorption and desorption process are settled by studying LiOH and HCl solutions. For both of the ion-sieves, the obtained results are found to be similar. The optimum conditions are get by studying at room temperature in 20 mins at pH = 12.40 with the initial concentration of 20 mg/L. The optimum adsorbent dosage was chosen as 0.1 g. The studied conditions for the desorption of Li+ are the same as with the adsorption process. Although the desorption yield was increased by increasing temperature, the extraction experiments of lithium from the sieves were performed at room temperature to avoid too much dissolution of Mn and Ni from the sieves. The defined conditions were applied to borogypsum solution and all Li+ in the solution was tried to uptake by these sieves. The results are given in Table 9.
Fig. 17. Desorption yield of the lithium with the different adsorbent dosages by lithium ion-sieves.
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Table 8 Mn and Ni dissolution ratios of ion-sieves during the desorption process at adsorbent dosage study. Adsorbent Dosage (g) 0.1 0.2 0.3 0.4 0.5
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
8.65 8.78 8.45 8.17 7.80
1.35 1.27 1.25 1.19 1.16
1.06 1.19 1.15 1.12 1.11
Table 9 Li+ adsorption yield of ion-sieves from borogypsum, desorption yield and Mn, Ni dissolution ratios. Ion-sieve
The amount of Li+ in borogypsum solutionsa (mg/L)
The amount of Li+ adsorbeda (mg/L)
Adsorption yield (%)
Desorption yield (%)
Mn dissolution ratio (%)a
Ni dissolution ratio (%)a
l-MnO2
21.17 0.06 20.48 0.06
20.86 0.05 6.55 0.04
98.54 31.98
97.75 65.95
6.19 0.01 0.85 0.01
– 2.15 0.03
Ion-sieve S– N a
The results are the average of the 3 repetitions.
Li+ was adsorbed from the borogypsum solution by l-MnO2 with 98.54% of adsorption yield and the study was succeeded in giving up the 97.75% of the adsorbed amount. The obtained results are in the same order with the results obtained from the synthetic solution. After lithium in borogypsum was taken into solution, Ca was removed as CaCO3 by adding Na2CO3 into the solution and the other cations were precipitated as their hydroxides during the pH optimization. The solution was so rich by Na+ and SO42 ions. As the sieves known as a selective ion-sieves for lithium, adsorption process was not affected by the occurrence of these ions. The influence of ionic strength on the adsorption of lithium by the ionsieves was investigated by the Wang et al. [1]. They have changed the concentration of Na+ from 1000 to 50,000 ppm to see the effect of this ion on the lithium adsorption and it was found that the ion sieves showed high selectivity to lithium among the large amounts of Na+. By the ion-sieve SN 31.98% of the lithium in the solution was adsorbed and 65.95% of the adsorbed amount of lithium was given up. The Li+ adsorption / extraction properties of this ion-sieve is quite low due to the cell-contraction and as a result it is also possible to see the lower manganese dissolution. With this ion sieve this ratio is 0.85 %. The Ni dissolution ratio is also at the same level with the dissolution ratios when studied with the LiOH solution. 4. Conclusions
l-MnO2 and ion-sieve SN were prepared as a selective adsorbent for Li+ uptake. Their structures, stabilities and Li+ adsorption properties from the LiOH solution and borogypsum solution and desorption conditions were studied. The results are summarized as follows: a XRD and SEM analyses show that substituting some of the manganese with nickel in order to reduce the manganese dissolution from the sieve does not destroy the spinel structure or effect the morphology. b LiMn2O4 and LiNi0.5Mn1.5O4 maintain their structure and morphology after acid treatment. The incorporation of Ni into the structure decreases Mn dissolution from the spinel, at the
same time it decreases Li+ extraction and adsorption substantially. c l-MnO2 has a higher adsorption capacity than the ion-sieve SN. The Li+ adsorption data of both ion sieves as a function of equilibrium concentrations at room temperature were fitted to the Langmuir isotherm equation but the l-MnO2 shows the highest correlation. d With both ion-sieves, equilibrium was reached within 20 mins. This result is quite short when compared to the literature. This can attributed to the ion-sieves being nanosized and the studied concentrations were being higher than the solutions studied in literature. The solution was also not complex by other ions. e Both of the ion-sieves have advantages and disadvantages. l-MnO2 has a higher adsorption capacity and Mn dissolution ratio. At each use, the dissolution of Mn continues, and as a result the ion-sieve loses its ability to adsorb Li+. Ion-sieve SN maintains its structure for a longer time but its Li+ adsorption capacity is significantly less when compared with l-MnO2.
References [1] L. Wang, C.-G. Meng, M. Han, W. Ma, Lithium uptake in-fixed pH solution by ion sieves, J. Colloid Interface Sci. 325 (1) (2008) 31–40, doi:http://dx.doi.org/ 10.1016/j.jcis.2008.05.005. [2] K. Yoshizuka, Benchmark evaluation of selective recovery of lithium from seawater, Separation & recovery of metals and biomolecules Hacettepe University Workshop Programme, September, Ankara, 2008. [3] L. Wang, C.G. Meng, W. Ma, Study on Li+ uptake by lithium ion—sieve via the pH technique, Colloids Surf. A Physicochem. Eng. Aspects 334 (1–3) (2009) 34–39, doi:http://dx.doi.org/10.1016/j.colsurfa.2008.09.050. [4] R. Chitrakar, H. Kanoh, Y. Miyai, K. Ooi, Recovery of lithium from seawater using manganese oxide adsorbent (H1.6Mn1.6O4) derived from Li1.6Mn1.6O4, Ind. Eng. Chem. Res. 40 (9) (2001) 2054–2058, doi:http://dx.doi.org/10.1021/ie000911h. [5] A. Umeno, Y. Miyai, N. Takagi, R. Chitrakar, K. Sakane, K. Ooi, Preparation and adsorptive properties of membrane-type adsorbents for lithium recovery from seawater, Ind. Eng. Chem. Res. 41 (17) (2002) 4281–4287, doi:http://dx.doi. org/10.1021/ie010847j. [6] L.-W. Ma, B.-Z. Chen, X.-C. Shi, W. Zhang, K. Zhang, Stability and Li+ extraction/ adsorption properties of LiMxMn2xO4 (M = Ni, Al, Ti; 0 x 1) in aqueous solution, Colloids Surf. A Physicochem. Eng. Aspects 369 (1–3) (2010) 88–94. [7] L. Tian, W. Ma, M. Han, Adsorption behavior of Li+ onto nano-lithium ion sieve from hybrid magnesium/lithium manganese oxide, Chem. Eng. J. 156 (1) (2010) 134–140, doi:http://dx.doi.org/10.1016/j.cej.2009.10.008. an, M. Çolak, I. Gündog an, Presence and distribution of [8] C. Helvacı, H. Mordog lithium in borate deposits and some recent lake waters of west-central Turkey, Int. Geol. Rev. 46 (2) (2004) 177–190, doi:http://dx.doi.org/10.2747/00206814.46.2.177.
an / Journal of Environmental Chemical Engineering 3 (2015) 2670–2683 F. Özmal, Y. Erdog an, M. Aksu, A. Demirbaş, Y. Abalı, Analyses of boronic ores and sludges [9] Y. Erdog and solubilities of boron minerals in CO2-saturated water, Res. Conserv. Recycling 24 (3–4) (1998) 275–283, doi:http://dx.doi.org/10.1016/S0921-3449 (98)00045-7. [10] L. Wang, W. Ma, R. Liu, H.Y. Li, C.G. Meng, Correlation between Li+ adsorption capacity and the preparation conditions of spinel lithium manganese precursor, Solid State Ionics 177 (17–18) (2006) 1421–1428, doi:http://dx.doi.org/ 10.1016/j.ssi.2006.07.019. [11] R. Chitrakar, H. Kanoh, Y. Miyai, K. Ooi, A new type of manganese oxide (MnO2.0.5H2O) derived from Li1.6Mn1.6O4 and its lithium ion-sieve properties, Chem. Mater. 12 (10) (2000) 3151–3157, doi:http://dx.doi.org/10.1021/ cm0000191. [12] X.J. Yang, H. Kanoh, W.P. Tang, K. Ooi, Synthesis of Li1,33Mn1,67O4 spinels with different morphologies and their ion adsorptivities after delihiation, J. Mater. Chem. 10 (8) (2000) 1903–1909, doi:http://dx.doi.org/10.1039/b000219o. [13] H.J. Choi, K.M. Lee, J.G. Lee, LiMn1.95M0.05O4 (M: Al, Co, Fe, Ni, Y) cathode materials prepared by combustion synthesis, J. Power Sources 103 (1) (2001) 154–159, doi:http://dx.doi.org/10.1016/S0378-7753(01)00835-7. [14] G. Fey, Preparation and electrochemical properties of high-voltage cathode materials, LiMyNi0.5yMn1.5O4 (M = Fe, Cu, Al, Mg; y = 0.0–0.4), J. Power Sources 115 (2) (2003) 332–345, doi:http://dx.doi.org/10.1016/S0378-7753(03)000107.
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[15] Y. Shao-Horn, Redox reactions of cobalt, aliminum and titanium substituted lithium manganese spinel compounds in lithium cells, Solid State Ionics 139 (1–2) (2001) 13–25, doi:http://dx.doi.org/10.1016/S0167-2738(00)00817-1. [16] Q. Feng, Y. Miyai, H. Kanoh, K. Ooi, Li+ extraction/insertion with spinel-type lithium manganese oxides. Characterization of redox-type and ion-exchangetype sites, Langmuir 8 (7) (1992) 1861–1867, doi:http://dx.doi.org/10.1021/ la00043a029. [17] Q. Feng, H. Kanoh, Y. Miyai, K. Ooi, Li+ Extraction/Insertion Reactions with LiZn0.5Mn1.5O4 Spinel in the Aqueous Phase, Chem. Mater. 7 (2) (1995) 379– 384, doi:http://dx.doi.org/10.1021/cm00050a023. [18] K.K. Singh, R. Rastogi, S.H. Hasan, Removal of Cr(VI)from wastewater using rice bran, J. Colloid Interface Sci. 290 (1) (2005) 61–68, doi:http://dx.doi.org/ 10.1016/j.jcis.2005.04.011. [19] Z. Chen, W. Ma, M. Han, Biosorption of nickel and copper onto treated alga (Undaria pinnatifida): application of isoterm and kinetic models, J. Hazard. Mater. 155 (1–2) (2008) 327–333, doi:http://dx.doi.org/10.1016/j.jhazmat.2007.11.064. [20] A. Ahmad, M. Rafatullah, O. Sulaiman, M.H. Ibrahim, Y.Y. Chii, B.M. Siddique, Removal of Cu(II) and Pb(II) ions from aqueous solution by adsorption on sawdust of meranti wood, Desalination 247 (1–3) (2009) 636–646, doi:http:// dx.doi.org/10.1016/j.desal.2009.01.007.
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Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece
Li+ adsorption/desorption properties of lithium ion-sieves in aqueous solution and recovery of lithium from borogypsum anb Ferda Özmala,* , Yunus Erdog a b
Department of Biochemistry, Dumlupınar University, Kütahya 43100, Turkey Department of Chemistry, Dumlupınar University, Kütahya 43100, Turkey
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 July 2015 Received in revised form 18 September 2015 Accepted 28 September 2015 Available online 9 October 2015
This study presents the recovery of lithium from borogypsum by lithium ion-sieves known as selective adsorbents. In the study two types of ion-sieves were used. One was l-MnO2 which was obtained by the treatment of LiMn2O4 with acid and the other was prepared via the acid treatment of LiNi0.5Mn1.5O4 which occurred by the substitution some of manganese with nickel. Besides the lithium adsorption and desorption capacities, manganese and nickel dissolution ratios from the spinel powders were also studied. Optimum adsorption and desorption conditions were determined in the LiOH and HCl solutions. XRD and SEM analyses showed that substitution of manganese with nickel and treatment of spinel powders with acid did not destroy the spinel structure and morphology. Because of the cell-contraction, nickel-substituted spinel did not show any satisfying Li+ extraction and adsorption properties. ã 2015 Elsevier Ltd. All rights reserved.
Keywords: Borogypsum Lithium Ion-sieve Adsorption Desorption yield Manganese dissolution ratio
1. Introduction In recent years lithium has a great importance because of its strategic value in different usage areas. It is mainly used for electrical vehicles, aircrafts as a light alloy when mixed with Al, rechargeable batteries for mobile devices and nuclear fusions [1–3]. According to the 6Li + n ! 3T + 4He reaction, being an alternative energy fuel of future has increased the interest on lithium. Its main reserves are spodumene, petallite, lepidolite, amblygonite minerals and brines. However, these reserves are not sufficient to overcome the demand for lithium in the near future. Seawater is considered as a vast source of lithium by many researchers and many studies have been performed although its concentration in seawater is very low (0.17 mg/L) [3–7]. In Turkey, lithium is mostly found in the clay minerals in borate deposits and in the salt lakes. Investigations have shown that both the waters of Tuzgölü Lake and the clays associated with boron minerals are the potential lithium resources inTurkey [8]. According to our previous studies, industrial boron wastes contain at least 300–600 mg/kg Li+[8,9]. In addition to these reserves, industrial boron wastes are very important potential for lithium production. Recovering lithium from a source that is classified as a waste is so economical and contributes at solving an environmental problem.
* Corresponding author: Fax: +90 2742652056. E-mail addresses: [email protected] (F. Özmal), an). [email protected] (Y. Erdog http://dx.doi.org/10.1016/j.jece.2015.09.024 2213-3437/ ã 2015 Elsevier Ltd. All rights reserved.
Borogypsum is a by-product in the production process of boric acid. According to the following reaction: 2CaO.3B2O3.5H2O + 2H2SO4 + 6H2O ! 6H3BO3 + 2CaSO4.2H2O
(1)
to produce a tonne of boric acid, 1.5 tones of colemanite is fed in to the process and 0.5 tonne of borogypsum is produced as waste. The boric acid production rate of Emet Boron Process Management of Turkey is known as 240,000 tones a year and the waste amount is about 120,000 tones. Utilizing this waste by recovering the valuable metals such as lithium may be very economical because the amount of lithium in this source is nearly 1500 times greater than the amount in seawater. To recover the lithium from borogypsum, spinel type manganese oxides were used in the study. These oxides were preferred because of their high affinity to the Li+ only, high stability, low toxicity and low cost [3,6,10]. By the treatment of LiMn2O4 with an acid solution a new structure referred as l-MnO2 can be obtained. In this new structure all the lithium at the tetrahedral sites goes out and an ion-sieve, l-MnO2, occurs. This structure can take the Li+ back from the solution among the other ions selectively [6]. There is a restriction in the usage of LiMn2O4 due to the Mn dissolution. During the Li+ extraction by acid treatment Mn3+ disproportionate to Mn2+ and Mn4+ according to the following reaction: 2Mn3+ ! Mn2+ + Mn4+
(2)
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Mn4+ remains in the structure and keeps the structure from being destroyed during the formation of l-MnO2 while the Mn2+ effects the structure negatively by dissolving [6]. As the Mn is dissolved at each usage, the spinel structure looses its property being an ion-sieve. Several methods have been considered to overcome this problem. One of them is the synthesis of the spinel structures including tetravalent manganese only. These kind of manganese oxides are known as having high lithium adsorption capacity and low manganese dissolution ratio but the process for synthesizing these materials is quite difficult [11,12]. Cation substitution is another way for solving the problem. By this method average valence of manganese increases and the spinel structure comes closer to the structures containing Mn4+ only. It is also possible to decrease the Mn dissolution ratio [13,14]. In this study LiMn2O4 and a cation substituted spinel, LiNi0.5Mn1.5O4, are studied. Their structures, stability and morphologies were investigated before and after acid treatment. Mn and Ni dissolution ratios after acid treatment, Li+ adsorption properties from LiOH solution, borogypsum solution and desorption yields were also investigated and the results of both spinels were compared to each other.
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2.3. Characterization The chemical analyses of borogypsum was performed by (Rigaku ZSX Primus) XRF and (Varian AA240FS) AAS. The crystalline phases of the powders before and after acid treatment were determined by X-ray analysis (Rigaku-miniflex) at a speed of 2 /min and 0.01 steps, by using CuKa radiation between 2 and 70 . To investigate the differences between the morphologies of the powders and the ion-sieves, a scanning electron microscope (SEM) (Zeiss Supra 50 VP) was used. 2.4. Li+ adsorption / desorption process from solution by batchwise
2. Experimental
A constant mass of l-MnO2 and the ion-sieve SN were immerged in 25 ml of LiOH solution at 22 C for 2 h. The lithium ion concentration was 200 mg/L. pH varied from 4 to 12.40 which is the original pH value of LiOH solutions at the studied concentration. The ion-sieves were separated from the solutions by filtration with membrane filters with pore size of 200 nm (Schleicher & SchuellNL 16) after attainment of the equilibrium and the equilibrium lithium concentrations in the solution were determined by ICPOES. The lithium adsorption capacities of these ion-sieves were calculated using the following equation.
2.1. Materials
Qe ¼
LiMn2O4 and LiNi0.5Mn1.5O4 spinel powders (more than 99%) were obtained from Sigma-Aldrich with pore size less than 0.5 mm. Borogypsum, the waste from Emet Boric Acid Plant, was used as a lithium source. It was obtained from the waste pool of the plant in mud form.
where Qe is the lithium adsorption capacity; C0 and Ce are the initial and equilibrium Li+ concentrations in the solution, respectively; V is the solution volume and m is the weight of the dry ion-sieves. The optimum adsorption time, temperature, initial concentration and adsorbent dosage were also studied to obtain the maximum recovery of lithium. Desorption of lithium from ion-sieves is achieved with 0.1 M HCl. Constant mass of LiMn2O4 and LiNi0.5Mn1.5O4 (by the insertion of lithium into ion-sieves, ion-sieves turn to their initial form) was immerged in HCl solution. All the other conditions in the desorption process are same as the ones in adsorption process. After the desorption process is completed lithium concentrations were determined in the acid solutions. The optimum adsorption and desorption conditions were decided with LiOH and HCl solutions, then these conditions were adapted to the experiments performed with borogypsum.
2.2. Preparation of ion-sieves and borogypsum 0.1 g of both LiMn2O4 and LiNi0.5Mn1.5O4 spinel powder were immerged in 25 ml of HCl and HNO3 solutions at different concentrations (0.1–0.5 M) at 25 C for 24 h. The lithium and manganese concentrations of both spinels and nickel concentrations for LiNi0.5Mn1.5O4 were determined in the filtrate solutions after acid treatment. Lithium, manganese and nickel concentrations were detected by an inductively coupled plasma spectrometer (ICP) (PerkinElmer, 4300 DV). These metals dissolution ratios (Rdis.) from the spinel powders were calculated using the following Eq. (3). Rdis ¼
mfiltrate mtheorical
C0 Ce m
ð4Þ
2.5. Equilibrium isotherm ð3Þ
where mfiltrate is the mass of metallic elements in the filtrate solution after acid treatment in the unit of mg/L, mtheorical is the total metal mass in the studied amount of spinel powder at constant solution volume. LiMn2O4 and LiNi0.5Mn1.5O4 spinels were turned to lithium ionsieves after acid treatment. They were designated as l-MnO2 and the ion-sieve SN, respectively. Acid treatment experiments showed that using 0.1 M HCl solution is most suitable for delithiating the spinel powders. A stock mass of ion- sieves were prepared for both spinels using 10 g of powder and 2.5 L of HCl for 24 h. Then the acid-treated materials were filtered with pore 4, washed with deionized water and dried at 100 C overnight to obtain the final ion-sieves. Borogypsum was dried at 110 C for 48 h. After that it was grinded to the pore size of 63 mm and the experiments were performed to decide the optimum dissolution conditions of borogypsum.
A constant mass (0.1 g) of l-MnO2 and ion-sieve SN were immerged in a series of LiOH solutions (25 ml) at room temperature for 20 mins. The pH of the solutions was fixed to 12.40 while the lithium concentrations were changed between 10 and 200 mg/L. The Langmuir isotherm equation was used to characterize the uptake properties of the ion-sieves. The isothermal equation is expressed as: Ce 1 1 ¼ Ce þ KLQ m Qe Qm
ð5Þ
where Ce is the equilibrium Li+ concentration of the solution, Qe is the equilibrium Li+ adsorption capacity, Qm is the theoretical maximum adsorption capacity and the KL is the Langmuir empirical constant. The values of Qm and KL can be calculated from the slope and intercept of plot of Ce/Qe vs. Ce. 2.6. Adsorption/ desorption of lithium from borogypsum 10 g of borogypsum which was calcined at 600 C for 60 min was immerged in 50 ml of 0.1 M HCl solution and refluxed for 2 h.
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Table 1 XRF results for the borogypsum.
Table 2 AAS results for the trace elements in borogypsum.
Components
% (W)
Detection limit
Components
mg/kg
Na2O MgO Al2O3 SiO2 P2O5 SO3 Cl F K2O CaO TiO2 MnO Fe2O3 ZnO As2O3 SrO B2O3a Ignition loss
0.0469 1.89 1.15 7.36 0.0280 37.5 0.0421 0.224 0.679 27.7 0.0789 0.0109 0.609 0.0048 0.400 1.17 2.13 19.20
0.0070 0.0074 0.0027 0.0041 0.0014 0.0060 0.0021 0.0718 0.0013 0.0042 0.0069 0.0029 0.0023 0.0012 0.0013 0.0009 – –
Li Rb Cs Cr Co Cu Y Cd Ba La Ce Pb Ni Th
295 5 90 2 116 3 3.0 0.6 <0.27 <0.13 1.0 0.5 <0.05 90 9 1.5 0.7 6.0 1.1 8.0 1.9 <0.30 <2.4
a
B2O3 analysis was performed at Emet boric acid plant by volumetric method.
The solution was filtered and Li, Mn and Ca analyses were performed in the filtrate solution. Then Na2CO3 was added to the solution and CaCO3 was filtered and removed from the solution while the lithium and manganese concentrations did not change. After that the solution was diluted at the 1/2 ratio. By this way, it became possible to study at the concentration at which the adsorption and desorption yields are very high (20 ppm). The solution pH was adjusted to 12.40 and as increasing the pH, there became an intensive precipitation in the solution. After the last filtration process, the solution was ready to use in the adsorption experiments. Before the solution was added on the ion-sieves lithium, manganese and nickel concentrations in the solution was detected again and it was seen that all the manganese in the
solution was precipitated while the lithium concentration was still constant. Because of the negative effect of the magnesium on the lithium adsorption from the solutions, the magnesium amount in the solution was also controlled and it was found that there was no magnesium in the solution. Then, 0.1 g ion-sieve was immerged in 25 ml of the prepared solution. It was mixed at 500 rev/min for 20 min at room temperature and filtred by membrane filters. The ion sieves which adsorbed lithium in their structure were dried on filters overnight and delithiated with 0.1 M HCl. 3. Results and discussion 3.1. Chemical analyses of borogypsum Table 1 shows XRF analysis of major elements in borogypsum and Table 2 shows the trace elements concentrations in the sample by AAS.
Fig. 1. XRD patterns of LiMn2O4 and LiNi0.5Mn1.5O4.
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Fig. 2. XRD patterns of LiMn2O4 before and after acid treatment.
3.2. Stability of LiMn2O4 and LiNi0.5Mn1.5O4 3.2.1. Structural analyses of LiMn2O4 and LiNi0.5Mn1.5O4 Fig. 1 shows the XRD patterns of LiMn2O4 and LiNi0.5Mn1.5O4. Ni in the spinel structure does not destroy the structure of the powder. XRD diffraction peaks of LiNi0.5Mn1.5O4 move to the higher angle direction according to the peaks of LiMn2O4. This result is attributed to cell contraction. Replacement of Mn3+ by Ni2+ creates a shrinkage at the lattice. By the substitution of Mn3+ with
Ni2+, some Mn3+ are oxidized to Mn4+ to keep the charge balance as Ni2+ has the lower valance than Mn3+. Ionic radius of Mn4+ is 0054 nm while the Mn3+ has an ionic radius of 0,0645 nm [15]. 3.2.2. Structure and morphology of LiMn2O4 and LiNi0.5Mn1.5O4 before and after acid treatment Fig. 2 shows the XRD patterns of LiMn2O4 before and after the acid treatment. By the acid treatment of LiMn2O4, Li+ extracts from
Fig. 3. XRD patterns of LiNi0.5Mn1.5O4 before and after acid treatment.
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Fig. 4. SEM images of LiMn2O4 (a) before and (b) after the acid treatment.
the structure and a spinel-type manganese oxide defined as l-MnO2 is prepared [16]. After the acid treatment, there is no change at the XRD patterns only the difference can be released as the shifting to the higher angle direction. This means that during the acid treatment, LiMn2O4 maintains its main structure but there becomes a cell contraction due to the Li+ extraction by the redox reaction [16]. Diffraction peaks of LiNi0.5Mn1.5O4 also indicate shifting to higher angle direction after acid treatment (Fig. 3). By substituting some of the manganese with Ni, the structure increases its Mn4+ content in order to keep its average valence as a result of which this spinel shows ion-exchange properties in Li+ extraction and insertion [17]. The differences between the ionic radii of Li+ (78 pm) and H+ (1,2 pm) are the reason of cell contraction. Figures 4 and 5 show the morphologies of LiMn2O4 and LiNi0.5Mn1.5O4 before and after the acid treatment, respectively. Both of the spinels, LiMn2O4 and LiNi0.5Mn1.5O4, have even and fine particles before acid treatment but it is possible to say that the particles of LiNi0.5Mn1.5O4 are thinner than the particles of LiMn2O4. The particle size of both of the spinels are less than 200 nm. After the acid treatment, we can say that the morphologies of the spinels are still the same as the ones before the acid treatment. The acid treatment has a little effect on increasing grain size and agglomeration [7]. Agglomeration is more
effective at the spinel with nickel because its particle size is less than the other. It is possible to say there is no change in the morphologies of the spinels by the acid treatment. 3.2.3. Mn dissolution of LiMn2O4 and LiNi0.5Mn1.5O4 2 Mn3+ ! Mn2+ + Mn4+ according to the disproportion reaction Mn4+ remains in the structure to form l-MnO2 and the Mn2+ is the manganese that is responsible from the dissolution in the acid solutions. When Mn3+ substitutes with nickel, the amount of Mn3+ that turns to Mn2+ reduces. That is the reason why LiNi0.5Mn1.5O4 is more stable in acid solutions than LiMn2O4. Figs. 6 and 7 show the metallic dissolution ratios (Mn, Ni) of spinel powders with different acid solutions. For both of the powders studying with 0.1 M HCl is more suitable. At this concentration the ion-sieves show the lowest dissolution ratios. 3.3. Li+ adsorption of LiMn2O4 and LiNi0.5Mn1.5O4 from synthetic solution and desorption process 3.3.1. Effect of pH Lithium adsorption capacities of ion-sieves by batch tests from LiOH solution at different pH values were studied. The pH values of solution was changed from 4 to 12.40 which is the original pH value
Fig. 5. SEM images of LiNi0.5Mn1.5O4 (a) before and (b) after the acid treatment.
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Fig. 6. Mn dissolution ratios from LiMn2O4 with different acids and concentration.
of the solution at the studied concentration. The results are shown in Fig. 8. There is a gentle increase of adsorption capacity (q) between the pH 4–10 while the increase after pH 10 is quite rapid. The adsorption capacity reaches the maximum of 34.70 and 8.93 mg/g for l-MnO2 and ion-sieve SN, respectively. Desorption yield of the lithium from the l-MnO2 that is adsorbed at the higher pH values is also higher than the yield adsorbed at lower pH values. However, for the ion-sieve SN, there is a decrease after pH 10 (Fig. 9). Mn dissolution that occurs during the desorption of Li which is adsorbed on l-MnO2 at pH 12.40 is 10.42%. This value decreases with the decreasing pH (Table 3). At the lower pH values, the lithium adsorption capacity is also very small. (&) [MnIV2]O4 + n LiOH ! (Lin&1n) [Mn(III)nMn(IV)2-n] O4 + (n/2) H2O + (n/4) O2 (6)
In the reaction (6) the symbols (), [], & are 8a tetrahedralsites, 16 d octahedral sites and vacant sites, respectively [16]. According to the reaction, as the amount of lithium that is adsorbed on the l-MnO2 decreases, the amount of the Mn(III) in the LiMn2O4 also decreases. It is known that Mn dissolution from LiMn2O4 (LiMn3 + Mn4+O4) in acid solution proceeds as a disproportion: 2Mn3+ ! Mn2+ + Mn4+. The Mn4+ remains in the spinel skeleton to form l-MnO2 and Mn2+ dissolves in acid solution [6]. Due to the Ni2+ substituting of Mn3+, Mn4+ content of the spinel structure (LiNi0.5Mn1.5O4) becomes higher. So, lithium extraction process of the spinel can be attributed to Li+ H+ ion – exchange reaction substantially. By this way, the amount of Mn2+ which occurs by the disproportion reaction of Mn3+ is quite less. As the pH increases, the amount of Mn and Ni that extracted from the structure decrease (Table 3). The low lithium adsorption capacity
Fig. 7. Mn and Ni dissolution ratios from LiNi0.5Mn1.5O4 with different acids and concentrations.
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Fig. 8. Lithium adsorption capacities of ion-sieves from the solutions at different pH values (T = 22 C, ion-sieve mass = 0.1 g, CLi+ = 200 mg/L, V = 25 ml, t = 2 h).
of ion-sieve SN at low pH values can be explained by destroying of structure partly by dissolving of Mn and Ni from the sieve too much at low pH values. 3.3.2. Time dependence of the study Effect of time at the Li+ adsorption and desorption of ion-sieves at pH 12.40 and changing at the dissolution ratios of metallic elements from the ion-sieves by time were investigated. Fig. 10 illustrates the evolution at the uptake data of Li+ as function of time for both l-MnO2 and ion-sieve SN. It appears from Fig. 10 that experiment curves show a rapid initial rise of adsorption capacities (q). The maximum amount of uptake (91%) is achieved within 20 mins for l-MnO2 which is faster than Li+ uptake by other
ion-sieves from different Li+ solutions and seawater [3,4]. The reason could be ascribed to the higher Li+ concentration (200 mg/L) and being no cations for competition in the media. Also the purity of spinel powders are more than 99% and they are nano-sized powders and for LiMn2O4, the maximum desorption yield (90.36%) is also achieved within 20 mins (Fig. 11). This result is quite important when the cycle rate of a process is considered. Mn dissolution rate of LiMn2O4 increases with the time and reaches to value of 10.92% after 120 mins. To reach the maximum Li+ uptake in 20 mins is also very important for the manganese dissolution rate being less at this time period. Alltheexperimentsperformedfor l-MnO2 werereapeatedforionsieve SN. The results are closed with the results of l-MnO2.
Fig. 9. Desorption yield of the lithium that is adsorbed at different pH values by lithium ion-sieves. (CH+ = 0.1 mol/L)
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Table 3 Mn and Ni dissolution ratios of ion-sieves during the desorption process at pH study. pH
4 6 8 10 12.40
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
1.94 2.37 2.57 2.58 10.42
1.62 1.59 1.54 1.48 1.40
3.16 3.07 2.92 2.91 2.67
Adsorption reaches the equilibrium within the 20 mins. Also it is possible to reach the maximum desorption yield (67.76%) at the same period(Fig.11).Asthecontacttime of theacidincreases,the MnandNi dissolutionratiosoftheion-sivesalsoincrease(Table4).Theion-sieve having the maximum Li+ adsorption capacity at the time at which the metallic element dissolution rate is fewer is a great advantage for the ion-sieveinordertoincreasethelifetimeofthesieve.Itisknownthatas the metallic elements dissolve from the structure, the spinel powders lose their property of being an ion-sieve. 3.3.3. Effect of temperature Experiments were performed at different temperatures; 22, 30, 40, 50, 60 C. From the slopes in Fig. 12, we can see the increase at the Li+ adsorption capacity with the increasing of temperature. The results show the endothermic nature of the sorption. These spinel manganese oxide ion-sieves have plenty of pores and cavities; especially the cavities in tetrahedral 8a sites only permit the small ions to pass in and out, e.g., Li+ and H+[1]. Li+ sorption or insertion activity requires a diffusion process, which is an endothermic process. Increasing of the temperature supports the adsorbate transport within the pores of the adsorbent. On the other hand, for the exchange of Li+ and H+, firstly extraction of proton from the structure must be occurred. This is possible with the breaking of the bond between OH. The bond breaking is also an endothermic process [1]. Ion-exchange reaction can be written as (where S represents the main body of the sieve) RSOH+ Li+ $ RSOLi+ H+
(7)
Desorption yield increases with the increasing temperature for both of the ion-sieves (Fig. 13). Also, from the Table 5 it can be
clearly seen that at the desorption process at constant experimental period as the temperature increases Mn and Ni dissolution ratios of the sieves increase, correspondingly. Especially dissolution of manganese from l-MnO2 changes substantially from 7.30 to 11.44 while the increase at the ion-sieve SN is so smooth, 1.32– 1.70. The reason of manganese dissolution rate of ion-sieve SN being less than the l-MnO2 is due to the nickel creating cell contraction at the structure. But the dissolution of nickel with the increasing temperature from this sieve cannot be ignored. Its nickel dissolution ratios changes from 1.82 to 4.91%. As the temperature increases, the amount of lithium that is adsorbed and desorbed also increases. But this increase is not very significant as the values are close to each other. When the negative effect of temperature increase on the manganese and nickel dissolution is considered, studying at the room temperature is preferred. 3.3.4. Effect of initial concentration A rising trend of adsorption capacity can be seen with the increasing initial Li+ concentration in Fig. 14. For l-MnO2, this increase is quite significant while the increase for ion-sieve SN is changing slightly. For both of the ion-sieves, the sorption process is governed by two steps which are boundary layer diffusion and intraparticle diffusion. By increasing the initial concentration of lithium, the surface of the ion-sieve is contacted with more lithium, which resulted by the diffusion of the Li+ at a larger amount through the boundary layer in unit time. The boundary layer diffusion is more important in Li+ uptake by l-MnO2 as the intraparticle diffusion has the greatest effect in the ion-sieve SN [1,18].
Fig. 10. Lithium adsorption capacities of ion-sieves at different contact times (T = 22 C; ion-sieve mass = 0.1 g; pH 12.40; CLi+ = 200 mg/L; V = 25 ml).
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Fig. 11. Desorption yield of the lithium at different contact times by lithium ion-sieves.
Table 4 Mn and Ni dissolution ratios of ion-sieves during the desorption process at time dependency study. Time (min)
5 10 15 20 30 40 60 80 100 120
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
6.27 6.25 8.02 8.10 8.47 9.21 9.95 9.76 10.99 10.92
1.27 1.42 1.49 1.44 1.59 1.61 1.59 1.62 1.67 1.61
1.44 2.04 2.19 2.35 2.78 3.24 3.00 3.14 3.11 3.23
Fig. 12. Lithium adsorption capacities of ion-sieves at different temperatures (ion-sieve mass = 0.1 g; pH 12.40; t = 20 min., CLi+ = 200 mg/L; V = 25 ml).
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Fig. 13. Desorption yield of the lithium at different temperatures by lithium ion-sieves.
Table 5 Mn and Ni dissolution ratios of ion-sieves during the desorption process at temperature study. Temperature ( C)
22 30 40 50 60
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
7.30 8.92 11.10 11.40 11.44
1.32 1.40 1.50 1.59 1.70
1.82 2.09 3.02 3.33 4.91
Fig. 14. Lithium adsorption capacities of ion-sieves at different initial concentrations (ion-sieve mass = 0.1 g; pH 12.40; t = 20 min., T = 22 C; V = 25 ml).
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Fig. 15. Desorption yield of lithium at different initial concentrations by lithium ion-sieves.
Table 6 Mn and Ni dissolution ratios of ion-sieves during the desorption process at different initial concentrations. Initial concentration (mg/L)
10 20 40 100 150 200
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%
Ni dissolution ratio (%)
5.97 6.12 6.54 7.89 8.02 8.15
0.72 0.80 0.89 1.19 1.27 1.36
2.51 2.52 2.50 2.48 2.52 2.49
Fig. 16. Lithium adsorption capacities of ion-sieves at different adsorbent dosages (pH 12.40; t = 20 min., T = 22 C; C0 = 1000 mg/L; V = 25 ml).
an / Journal of Environmental Chemical Engineering 3 (2015) 2670–2683 F. Özmal, Y. Erdog Table 7 Langmuir isotherm model parameters for the adsorption of Li+ onto ion-sieves. Ion-sieve
qmax (mg g1)
r2
KL (L mg1)
l-MnO2
35.71 10.87
0.998 0.973
0.144 0.016
Ion-sieve S–N
Desorption yield of Li+ that is adsorbed by l-MnO2 decreased by increasing initial concentration. The reason can be ascribed to the studied constant concentration and volume of the acid used for desorption as the amount of lithium that is adsorbed by l-MnO2 changed by different initial concentrations. As shown in Fig. 15 desorption yield of the ion-sieve with nickel did not show a significant change by the initial concentration. Dissolution rate of manganese for both of the ion-sieves has increased with the increasing initial concentration. Reaction (6) describes the reason of rising. As the amount of Li+ that is adsorbed increases, the amount of Mn(III) also increases. After that, Mn(III) disproportionates to Mn4+ and Mn2+. Mn2+ is the form of manganese which is responsible from the manganese dissolution. The increase of the dissolution rate of manganese is lesser for the ion-sieve SN due to Li+ insertion and extraction reactions from the structure is considered to be the ion-exchange mostly. The dissolution rate of nickel is said to be nearly constant for this ionsieve (Table 6). The Li+ adsorption data of the ion-sieves as a function of equilibrium concentrations at 22 C were fitted to the Langmuir isotherm equation for both of the sieves (Table 7). The correlation coefficients (R2) of l-MnO2 and ion-sieve SN were calculated as 0.998 and 0.973, respectively. The isotherm coefficients Qm and KL can be obtained from the slope and the intercept of the linear plots. For l-MnO2, these values are 35.71 mg/g and 0.144 L/mg; for the ion-sieve SN the values are 10.87 mg/g ve 0.016 L/mg, respectively. The obtained values for l-MnO2 is greater than the values for ion-sieve with nickel. The reason is attributed to the l-MnO2’s higher performance at Li+ adsorption from the solution. 3.3.5. The effect of ion-sieve dose on recovery of lithium It is known that the adsorbent dose has a great influence in adsorption process because the number of binding sites in this
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process was indicated by the dose of the adsorbent added into the solution. At the same time, it also indicates the number of Li+ insertion sites [19,20]. The results are shown at Fig. 16. As the dose of adsorbent increases from 0.1 to 0.5 g, the amount of adsorbed Li+ decreases. The reason can be attributed to the unsaturation of adsorption sites and particle interaction. As seen clearly from Fig. 17 desorption yield increases by the increasing adsorbent dosage because absorbent surface area of the adsorbent increases with increasing dosage. For both ion-sieves, increasing the dose after 0.4 g does not create a significant change at the amount of the Li+ adsorbed. This means that the equilibrium is established between the adsorbent and Li+ at this dosage. At l-MnO2 by the increasing dose the amount of Mn3+ and Mn2+ decreases because the amount of lithium that is adsorbed also decreases. At the ion-sieve SN, ion-exchange reaction is most effective than redox reaction so as the amount of lithium that is adsorbed decreases by the increasing dose, the amount of Li+ that exchanges with the H+ decreases, too. This is the reason for the slight decrease of Mn2+ and Ni+ dissolution with increasing adsorbent dosage (Table 8). 3.4. Li+ adsorption of LiMn2O4 and LiNi0.5Mn1.5O4 from borogypsum solution and desorption process To determine the maximum lithium adsorption capacity and desorption yield of ion-sieves, optimum conditions at the adsorption and desorption process are settled by studying LiOH and HCl solutions. For both of the ion-sieves, the obtained results are found to be similar. The optimum conditions are get by studying at room temperature in 20 mins at pH = 12.40 with the initial concentration of 20 mg/L. The optimum adsorbent dosage was chosen as 0.1 g. The studied conditions for the desorption of Li+ are the same as with the adsorption process. Although the desorption yield was increased by increasing temperature, the extraction experiments of lithium from the sieves were performed at room temperature to avoid too much dissolution of Mn and Ni from the sieves. The defined conditions were applied to borogypsum solution and all Li+ in the solution was tried to uptake by these sieves. The results are given in Table 9.
Fig. 17. Desorption yield of the lithium with the different adsorbent dosages by lithium ion-sieves.
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Table 8 Mn and Ni dissolution ratios of ion-sieves during the desorption process at adsorbent dosage study. Adsorbent Dosage (g) 0.1 0.2 0.3 0.4 0.5
LiMn2O4
LiNi0.5Mn1.5O4
Mn dissolution ratio (%)
Mn dissolution ratio (%)
Ni dissolution ratio (%)
8.65 8.78 8.45 8.17 7.80
1.35 1.27 1.25 1.19 1.16
1.06 1.19 1.15 1.12 1.11
Table 9 Li+ adsorption yield of ion-sieves from borogypsum, desorption yield and Mn, Ni dissolution ratios. Ion-sieve
The amount of Li+ in borogypsum solutionsa (mg/L)
The amount of Li+ adsorbeda (mg/L)
Adsorption yield (%)
Desorption yield (%)
Mn dissolution ratio (%)a
Ni dissolution ratio (%)a
l-MnO2
21.17 0.06 20.48 0.06
20.86 0.05 6.55 0.04
98.54 31.98
97.75 65.95
6.19 0.01 0.85 0.01
– 2.15 0.03
Ion-sieve S– N a
The results are the average of the 3 repetitions.
Li+ was adsorbed from the borogypsum solution by l-MnO2 with 98.54% of adsorption yield and the study was succeeded in giving up the 97.75% of the adsorbed amount. The obtained results are in the same order with the results obtained from the synthetic solution. After lithium in borogypsum was taken into solution, Ca was removed as CaCO3 by adding Na2CO3 into the solution and the other cations were precipitated as their hydroxides during the pH optimization. The solution was so rich by Na+ and SO42 ions. As the sieves known as a selective ion-sieves for lithium, adsorption process was not affected by the occurrence of these ions. The influence of ionic strength on the adsorption of lithium by the ionsieves was investigated by the Wang et al. [1]. They have changed the concentration of Na+ from 1000 to 50,000 ppm to see the effect of this ion on the lithium adsorption and it was found that the ion sieves showed high selectivity to lithium among the large amounts of Na+. By the ion-sieve SN 31.98% of the lithium in the solution was adsorbed and 65.95% of the adsorbed amount of lithium was given up. The Li+ adsorption / extraction properties of this ion-sieve is quite low due to the cell-contraction and as a result it is also possible to see the lower manganese dissolution. With this ion sieve this ratio is 0.85 %. The Ni dissolution ratio is also at the same level with the dissolution ratios when studied with the LiOH solution. 4. Conclusions
l-MnO2 and ion-sieve SN were prepared as a selective adsorbent for Li+ uptake. Their structures, stabilities and Li+ adsorption properties from the LiOH solution and borogypsum solution and desorption conditions were studied. The results are summarized as follows: a XRD and SEM analyses show that substituting some of the manganese with nickel in order to reduce the manganese dissolution from the sieve does not destroy the spinel structure or effect the morphology. b LiMn2O4 and LiNi0.5Mn1.5O4 maintain their structure and morphology after acid treatment. The incorporation of Ni into the structure decreases Mn dissolution from the spinel, at the
same time it decreases Li+ extraction and adsorption substantially. c l-MnO2 has a higher adsorption capacity than the ion-sieve SN. The Li+ adsorption data of both ion sieves as a function of equilibrium concentrations at room temperature were fitted to the Langmuir isotherm equation but the l-MnO2 shows the highest correlation. d With both ion-sieves, equilibrium was reached within 20 mins. This result is quite short when compared to the literature. This can attributed to the ion-sieves being nanosized and the studied concentrations were being higher than the solutions studied in literature. The solution was also not complex by other ions. e Both of the ion-sieves have advantages and disadvantages. l-MnO2 has a higher adsorption capacity and Mn dissolution ratio. At each use, the dissolution of Mn continues, and as a result the ion-sieve loses its ability to adsorb Li+. Ion-sieve SN maintains its structure for a longer time but its Li+ adsorption capacity is significantly less when compared with l-MnO2.
References [1] L. Wang, C.-G. Meng, M. Han, W. Ma, Lithium uptake in-fixed pH solution by ion sieves, J. Colloid Interface Sci. 325 (1) (2008) 31–40, doi:http://dx.doi.org/ 10.1016/j.jcis.2008.05.005. [2] K. Yoshizuka, Benchmark evaluation of selective recovery of lithium from seawater, Separation & recovery of metals and biomolecules Hacettepe University Workshop Programme, September, Ankara, 2008. [3] L. Wang, C.G. Meng, W. Ma, Study on Li+ uptake by lithium ion—sieve via the pH technique, Colloids Surf. A Physicochem. Eng. Aspects 334 (1–3) (2009) 34–39, doi:http://dx.doi.org/10.1016/j.colsurfa.2008.09.050. [4] R. Chitrakar, H. Kanoh, Y. Miyai, K. Ooi, Recovery of lithium from seawater using manganese oxide adsorbent (H1.6Mn1.6O4) derived from Li1.6Mn1.6O4, Ind. Eng. Chem. Res. 40 (9) (2001) 2054–2058, doi:http://dx.doi.org/10.1021/ie000911h. [5] A. Umeno, Y. Miyai, N. Takagi, R. Chitrakar, K. Sakane, K. Ooi, Preparation and adsorptive properties of membrane-type adsorbents for lithium recovery from seawater, Ind. Eng. Chem. Res. 41 (17) (2002) 4281–4287, doi:http://dx.doi. org/10.1021/ie010847j. [6] L.-W. Ma, B.-Z. Chen, X.-C. Shi, W. Zhang, K. Zhang, Stability and Li+ extraction/ adsorption properties of LiMxMn2xO4 (M = Ni, Al, Ti; 0 x 1) in aqueous solution, Colloids Surf. A Physicochem. Eng. Aspects 369 (1–3) (2010) 88–94. [7] L. Tian, W. Ma, M. Han, Adsorption behavior of Li+ onto nano-lithium ion sieve from hybrid magnesium/lithium manganese oxide, Chem. Eng. J. 156 (1) (2010) 134–140, doi:http://dx.doi.org/10.1016/j.cej.2009.10.008. an, M. Çolak, I. Gündog an, Presence and distribution of [8] C. Helvacı, H. Mordog lithium in borate deposits and some recent lake waters of west-central Turkey, Int. Geol. Rev. 46 (2) (2004) 177–190, doi:http://dx.doi.org/10.2747/00206814.46.2.177.
an / Journal of Environmental Chemical Engineering 3 (2015) 2670–2683 F. Özmal, Y. Erdog an, M. Aksu, A. Demirbaş, Y. Abalı, Analyses of boronic ores and sludges [9] Y. Erdog and solubilities of boron minerals in CO2-saturated water, Res. Conserv. Recycling 24 (3–4) (1998) 275–283, doi:http://dx.doi.org/10.1016/S0921-3449 (98)00045-7. [10] L. Wang, W. Ma, R. Liu, H.Y. Li, C.G. Meng, Correlation between Li+ adsorption capacity and the preparation conditions of spinel lithium manganese precursor, Solid State Ionics 177 (17–18) (2006) 1421–1428, doi:http://dx.doi.org/ 10.1016/j.ssi.2006.07.019. [11] R. Chitrakar, H. Kanoh, Y. Miyai, K. Ooi, A new type of manganese oxide (MnO2.0.5H2O) derived from Li1.6Mn1.6O4 and its lithium ion-sieve properties, Chem. Mater. 12 (10) (2000) 3151–3157, doi:http://dx.doi.org/10.1021/ cm0000191. [12] X.J. Yang, H. Kanoh, W.P. Tang, K. Ooi, Synthesis of Li1,33Mn1,67O4 spinels with different morphologies and their ion adsorptivities after delihiation, J. Mater. Chem. 10 (8) (2000) 1903–1909, doi:http://dx.doi.org/10.1039/b000219o. [13] H.J. Choi, K.M. Lee, J.G. Lee, LiMn1.95M0.05O4 (M: Al, Co, Fe, Ni, Y) cathode materials prepared by combustion synthesis, J. Power Sources 103 (1) (2001) 154–159, doi:http://dx.doi.org/10.1016/S0378-7753(01)00835-7. [14] G. Fey, Preparation and electrochemical properties of high-voltage cathode materials, LiMyNi0.5yMn1.5O4 (M = Fe, Cu, Al, Mg; y = 0.0–0.4), J. Power Sources 115 (2) (2003) 332–345, doi:http://dx.doi.org/10.1016/S0378-7753(03)000107.
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[15] Y. Shao-Horn, Redox reactions of cobalt, aliminum and titanium substituted lithium manganese spinel compounds in lithium cells, Solid State Ionics 139 (1–2) (2001) 13–25, doi:http://dx.doi.org/10.1016/S0167-2738(00)00817-1. [16] Q. Feng, Y. Miyai, H. Kanoh, K. Ooi, Li+ extraction/insertion with spinel-type lithium manganese oxides. Characterization of redox-type and ion-exchangetype sites, Langmuir 8 (7) (1992) 1861–1867, doi:http://dx.doi.org/10.1021/ la00043a029. [17] Q. Feng, H. Kanoh, Y. Miyai, K. Ooi, Li+ Extraction/Insertion Reactions with LiZn0.5Mn1.5O4 Spinel in the Aqueous Phase, Chem. Mater. 7 (2) (1995) 379– 384, doi:http://dx.doi.org/10.1021/cm00050a023. [18] K.K. Singh, R. Rastogi, S.H. Hasan, Removal of Cr(VI)from wastewater using rice bran, J. Colloid Interface Sci. 290 (1) (2005) 61–68, doi:http://dx.doi.org/ 10.1016/j.jcis.2005.04.011. [19] Z. Chen, W. Ma, M. Han, Biosorption of nickel and copper onto treated alga (Undaria pinnatifida): application of isoterm and kinetic models, J. Hazard. Mater. 155 (1–2) (2008) 327–333, doi:http://dx.doi.org/10.1016/j.jhazmat.2007.11.064. [20] A. Ahmad, M. Rafatullah, O. Sulaiman, M.H. Ibrahim, Y.Y. Chii, B.M. Siddique, Removal of Cu(II) and Pb(II) ions from aqueous solution by adsorption on sawdust of meranti wood, Desalination 247 (1–3) (2009) 636–646, doi:http:// dx.doi.org/10.1016/j.desal.2009.01.007.