IMPC 2020: XXX International Processing Congress, Cape Town, South Africa, 18-22 October 2020

Recovery of from by chlorination roasting

P.F.A. Bragaa*, S.C.A. Françaa, C.P. Pintoa, G.D. Rosalesb aCenter for Mineral Technology – CETEM, Ministry of Science, Technology, Innovation and Communication, Av. Pedro Calmon, 900, CEP 21941-908, Rio de Janeiro, RJ, . bLaboratory for Extractive Metallurgy and Materials Synthesis (MESiMat), Faculty of Exact and Natural Sciences (FCEN) UNCUYO, Padre Jorge Contreras 1300, CP 550, Mendoza, Argentina. *Corresponding author: [email protected]

ABSTRACT

The growing market demand for lithium is mainly due to its use in the manufacture of batteries for electric or hybrid vehicles and portable equipment (smartphones, tablets, power tools, notebooks, etc.). Currently there is great interest in finding new sources of lithium and technologies for its utilization. Li-S batteries have received attention due to their theoretically high specific energy density, which is 3 to 5 times greater than that of Li-ion batteries. Unlike Li-ion batteries, whose main raw materials are and , the main raw material for Li-S batteries is . The anode used in Li-S batteries is metallic lithium, produced by a molten lithium chloride electrolysis process. The extraction of lithium from such as spodumene, previously abandoned in the 1990s for being uneconomical, has become attractive due to the increase in prices as well as the need for greater lithium purity of products made from lithium bearing . The main methods used for lithium recovery from spodumene ore include the sulfuric acid process, the alkaline process (lime or limestone as raw material) and the chlorination roasting process. Thermodynamic modeling using the HSC software 5.1 was conducted to predict different reactions that could occur during chlorination roasting of the spodumene/MgCl2+CaCl2 system. Lithium extraction from the solid obtained after the chlorination roasting was also investigated. The results of thermodynamic analysis provided a better understanding of the chlorination roasting process for lithium extraction. Metallurgical tests with mass ratio of 1:6 (spodumene:chlorides) and molar ratio of

2:1 (MgCl2:CaCl2) allowed over 95% recovery of the lithium contained in the spodumene concentrate.

Keywords: Spodumene, Lithium chloride, Chlorination roasting

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

1. Introduction

Lithium, the lightest of all metals, has approximately half the density of water and high electrochemical potential. Therefore, lithium has become a strategic material for making the latest generation of rechargeable batteries (Li-ion) for use in electronic devices and portable electrical tools. In Brazil, the occurrences of lithium are mainly associated with rocks, located in the states of Minas Gerais, Ceará, Rio Grande do Norte and Paraíba. The main pegmatite minerals bearing lithium are , spodumene, and . Spodumene is an aluminosilicate mineral

(LiAlSi2O6) with Li2O content of 1 to 1.5%. In Brazil, the compounds derived from its processing are mainly used to manufacture lubricating greases. At present, the extraction of lithium from pegmatites is economically feasible due to the gradual increase in demand and prices of lithium-based compounds, mainly for use in batteries for electrical and electronic equipment (Dessemond et al., 2019). Various studies have been conducted to find more efficient ways to extract lithium from minerals so as to reduce the operating costs, since these are generally higher than the cost of producing lithium from brine (Rosales et al., 2014; Li et al., 2019; Braga et al., 2020). Li-ion batteries first appeared at the end of the 1990s to power mobile phones, notebooks and electrical tools, and since the turn of the century they have been increasingly used in electrified means of transportation, such as bicycles, motor scooters, cars, buses and trucks, as well as in energy safety systems (ESS). However, electric vehicles (EVs) still have limited autonomy (maximum of 300 km) due to the storage capacity of their Li-ion batteries. New lithium batteries, such as Li-S batteries, have attracted attention because of their high theoretical specific energy density, which is 3 to 5 times greater than that of Li-ion batteries. But obstacles still exist to attain this high energy density in practice, mainly the high internal resistance and self-discharge (Bruce et al., 2012). Nevertheless, in comparison with existing Li-ion batteries, Li- S cells are safer, and when produced in industrial scale can have lower unit cost due to the plentiful availability of sulfur in the earth’s crust (Fotouhi et al., 2017). Unlike Li-ion batteries, whose principal raw materials are lithium carbonate and lithium hydroxide, the main raw material of Li-S batteries is lithium chloride. The anode used in Li-S batteries is made of metallic lithium, produced by the molten lithium chloride electrolysis process. El-Naggar et al. (1988) showed it is possible to extract lithium from spodumene by means of its reaction with the mineral tachyhydrite (2MgCl2.CaCl2.12H2O ), to produce lithium chloride as the final product. In turn, Barbosa et al. (2014) demonstrated the extraction of lithium from β-spodumene with Cl2 gas at temperatures of 1,000 to 1,100 °C in a fixed-bed reactor. Barbosa et al. (2015) also carried out experiments involving chlorination of β-spodumene with CaCl2, finding the optimal extraction conditions to be temperature of 900 °C and 120 min of chlorination roasting.

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

The objective of this study was to develop a preliminary processing route for direct production of lithium chloride from spodumene through reaction with calcium chloride and/or magnesium chloride.

2. Experimental

2.1. Raw material and reagents

The spodumene concentrate employed was supplied by Companhia Brasileira de Lítio and contained 4.5% Li2O and P80=74 µm. Spodumene naturally exists in the α form and can be transformed into its β form, which is more reactive, by heating to 1,150 °C.

The reagents used were anhydrous magnesium chloride (MgCl2), produced by Sigma-Aldrich, and calcium chloride dihydrate (CaCl2.2H2O), produced by Vetec.

2.2. Materials and process control

The tests for production of lithium chloride were conducted on bench scale and included the processes of ore beneficiation (milling and classification) and pyro and hydrometallurgy (roasting, aqueous leaching). The main devices used were a ball mill, Tyler series sieves, muffle furnace, hydraulic press and alumina and porcelain crucibles. The control of the experiment, through chemical analysis of the lithium, was performed by flame emission spectroscopy (FES), atomic absorption spectrometry (AAS), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD). The concentration of lithium in the solid samples was measured after solubilization of the samples with HF, H2SO4 and HCl. After the lithium extraction tests, the liquor products and residues were analyzed to evaluate the extraction according to Equation (1).

퐥퐢퐭퐡퐢퐮퐦 퐢퐧 퐩퐫퐞퐠퐧퐚퐧퐭 퐥퐢퐪퐮퐨퐫 (퐠) 퐋퐢 퐞퐱퐭퐫퐚퐜퐭퐢퐨퐧 (%) = ퟏퟎퟎ. (1) 퐥퐢퐭퐡퐢퐮퐦 퐢퐧 퐩퐫퐞퐠퐧퐚퐧퐭 퐥퐢퐪퐮퐨퐫(퐠) + 퐥퐢퐭퐡퐢퐮퐦 퐢퐧 퐫퐞퐬퐢퐝퐮퐞 (퐠) All chlorination roasting tests were performed in triplicate, and when the result had deviation greater than 5%, the test was repeated.

2.3. Thermodynamic study (HSC Chemistry 5.11)

The thermodynamic behavior of the α-spodumene/CaCl2 and MgCl2 systems was analyzed using the HSC Chemistry 5.11 software. This step is very important because it permits determining the viability of the reaction by the proposed system.

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

2.4. Experimental conditions and procedures

The tests were based on the descriptions of Medina and El-Naggar (1984) and El-Naggar et al. (1988), but instead of mineral tachyhydrite, we used a mixture of magnesium chloride and calcium chloride salts, which is more reactive than the mineral itself. The mixture of spodumene + chlorides, in predetermined proportions, was pressed in a hydraulic press to increase the contact between the solid phases, and then reacted in an alumina crucible at 1,150 °C in a muffle furnace. The clinker produced was then leached with water at 95 °C to extract the soluble lithium chloride. The chemical reactions applicable to this work are presented in equations (2), (3) and (4).

푀푔퐶푙2 + 퐻2푂 → 푀푔푂 + 퐻퐶푙 (2) ~1,050− 1,150 °퐶 훼 퐿푖 푂. 퐴푙 푂 . 4푆푖푂 훽 − 퐿푖 푂. 퐴푙 푂 . 4푆푖푂 (3) 2 2 3 2 ⍙ 2 2 3 2 1,150 °퐶 훽 퐿푖 푂. 퐴푙 푂 . 4푆푖푂 + 퐶푎퐶푙 + 4푀푔푂 2퐿푖퐶푙 + 퐶푎푂. 푀푔푂. 푆푖푂 + 3푆푖푂 . 2푀푔푂 + 퐴푙 푂 . 푀푔푂 (4) 2 2 3 2 2 ⍙ 2 2 2 3

Equation (2) describes the decomposition reaction of MgCl2 into MgO; equation (3) indicates the transformation of α-spodumene into β-spodumene (more reactive and friable); and equation (4) denotes the reaction between β-spodumene and CaCl2 and/or MgO for the formation of LiCl, silicates and aluminates. The reactions of equations (3) and (4) happen almost simultaneously.

2.3.1. Preliminary studies of chlorination and extraction of lithium We performed lithium extraction tests with 1 g of spodumene and 8 g of the mixture of chlorides (MgCl2 and CaCl2) with different molar ratios between magnesium chloride and calcium chloride (2:1, 1:1, 1:2, 1:0, 0:1). The mixtures, after homogenization, were placed in a porcelain crucible and submitted to heat treatment for 120 minutes at temperature of 1,150 °C. The resulting clinker was crushed with an agate mortar and pestle and leached in water for 240 minutes at 95 °C. We used a solid-liquid ratio of 10% (w/w) in the aqueous leaching. At the end of the leaching, the liquor and residue were separated by filtration and analyzed. All the assays were carried out in triplicate. The block diagram of Figure 1 shows the operational procedure (Braga et al., 2019).

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

Fig.1. Block diagram of the preliminary tests

Table 1 reports the operating conditions of the preliminary lithium extraction tests.

Table 1. Operating conditions of the preliminary lithium extraction tests Test Mass ratio Molar ratio Chlorination roasting Aqueous leaching (spodumene:chlorides) MgCl :CaCl T (°C) t (min) T (°C) t (min) 2 2 1 1:8 2:1 1,150 120 95 240 2 1:8 1:1 1,150 120 95 240 3 1:8 1:2 1,150 120 95 240 4 1:8 1:0 1,150 120 95 240 5 1:8 0:1 1,150 120 95 240

2.3.2. Complementary lithium extraction tests We performed complementary tests (Table 2) with the aim of optimizing the extraction by reducing the consumption of reagents. Calcination/extraction assays were carried out with mass ratios of 1:6 and 1:4, for molar ratios of 2:1 and 1:1 (MgCl2:CaCl2). Because the best lithium extraction was achieved with mass ratio of 1:6 (spodumene:chlorides) and molar ratio of 1:1 (MgCl2:CaCl2), we then performed tests for different roasting times (30, 60 and 90 min), to determine the optimal duration.

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

Table 2. Operating conditions of the complementary lithium extraction tests. Test Mass ratio Molar ratio Chlorination roasting Aqueous leaching (spodumene:chlorides) MgCl :CaCl T (°C) t (min) T (°C) t (min) 2 2 6 1:6 2:1 1,150 120 95 240 7 1:4 2:1 1,150 120 95 240 8 1:6 1:1 1150 120 95 240 9 1:4 1:1 1,150 120 95 240 10 1:6 2:1 1,150 30 95 240 11 1:6 2:1 1,150 60 95 240 12 1:6 2:1 1,150 90 25 240

3. Results and discussion

3.1. Thermodynamic studies

The effects of temperature on the reaction for extraction of lithium from the mineral α- spodumene using CaCl2 and MgCl2 are presented in Figure 6.

Fig.6. HSC model for the mixture β-spodumene/CaCl2+MgCl2.

Figure 6 indicates that the chlorination reaction with MgCl2+CaCl2 was thermodynamically favored in the entire temperature range proposed (25-1,200 °C), for a molar ratio of 1:1 (α-spodumene:

CaCl2 + 4MgO). According to the model of the HSC software, the reaction products were lithium chloride (LiCl), calcium and magnesium silicate (CaO.MgO.SiO2), magnesium aluminate

(MgO.Al2O3) and dioxide (SiO2). Based on these results, we propose that the reaction that occurs during calcination is:

훽 − 퐿푖2푂. 퐴푙2푂3. 4푆푖푂2 + 퐶푎퐶푙2 + 4푀푔푂 → 2퐿푖퐶푙 + 퐶푎푂. 푀푔푂. 푆푖푂2 + 3푆푖푂2. 2푀푔푂 + 퐴푙2푂3. 푀푔푂 (4)

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

These results corroborate those of the study of chlorination of spodumene with tachyhydrite carried out by El-Naggar et al. (1988), as well as the findings of Barbosa et al. (2015), involving chlorination of β-spodumene with CaCl2.

3.2. Preliminary tests

Figure 2 depicts the lithium extraction results of the preliminary tests, to ascertain the influence of the MgCl2:CaCl2 molar ratio on the recovery of lithium contained in the spodumene. We found that the presence of magnesium in a molar quantity greater than or equal to that of calcium (ratios of 2:1 or 1:1) afforded high recovery rates (>96%) of the lithium present in the mineral. This result is in accordance with the reaction of equation (4), proposed by El-Naggar et al. (1988), in which 4 moles of

MgO to 1 mol of CaCl2 is necessary. In the assays conducted with a single chloride species, i.e.,

MgCl2 or CaCl2, the lithium extraction values were low.

Fig.2. Extraction of lithium with different MgCl2:CaCl2 molar ratios and 1:8 spodumene:chlorides ratio.

The clinker produced in the test with mass ratio of 1:8 and molar ratio of 2:1 (MgCl2:CaCl2) was analyzed by X-ray diffraction (XRD). The resulting diffractogram in Figure 3 shows the presence of the minerals forsterite (F), spinel (S), cordierite (C), tachyhydrite (T) and sinjarite (J) in the leaching residue. No β-spodumene was observed, indicating its transformation into other species. LiCl has an amorphous form, so it is not detected by XRD.

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

Fig.3. X-ray diffraction patterns of the chlorination roasted sample

For the lithium extraction with mass ratio of 1:8 and molar ratio of 2:1 (MgCl2:CaCl2), the X- ray diffractogram in Figure 4 shows the presence of periclase minerals (P), forsterite (F), spinel (S), cordierite (C), brucite (B) and calcium aluminum oxide chloride (O). No peaks can be identified referring to the mineral species tachyhydrite and sinjarite, which are water-soluble minerals that probably were leached out.

Fig.4. X-ray diffraction patterns for the leaching residue

3.3. Complementary tests

The complementary tests had the objective of determining the influence of the mass ratio (spodumene:chlorides) on the recovery of lithium. Figure 4 shows it was possible to maintain high lithium extraction (97.46%) with mass ratio of 1:6 (spodumene:chlorides) and molar ratio of 2:1

(MgCl2:CaCl2). For the test with mass ratio of 1:4 (spodumene:chlorides) and molar ratio of 2:1

(MgCl2:CaCl2), there was a significant reduction of the lithium extraction (34.72%), probably due to the lower quantity of calcium chloride available for the reaction, even with the presence of magnesium. In this case, there was insufficient chloride for the reaction to form lithium chloride (LiCl), according to the stoichiometry presented in equation (4).

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

Fig.4. Extraction of lithium with different spodumene:chlorides mass ratios for each molar ratio.

Figure 5 shows the results of the roasting tests (1,150°C) with different heating times. For 30 minutes, the lithium extraction was 96.89%, similar to the levels after 60 and 90 minutes. These assays were carried out with mass ratio of 1:6 (spodumene:chlorides) and molar ratio of 2:1 (MgCl2:CaCl2).

Fig.5. Lithium extraction (%) in function of chlorination roasting time.

4. Conclusions

According to the model of the HSC software, the reaction products were lithium chloride

(LiCl), calcium and magnesium silicate (CaO.MgO.SiO2), magnesium aluminate (MgO.Al2O3) and silicon dioxide (SiO2). In XRD pattern of chlorination roasting product (clinker), α or β-spodumene were not observed, demonstrating its transformation into other species. LiCl has an amorphous form and is therefore not detected by XRD. LiCl was detected by AAS in the aqueous leach liquor. Based on the preliminary tests, the lithium extraction rates were greater than 96% with a mixture of chlorides, provided that magnesium was present in a molar ratio greater than or equal to that of calcium, i.e., for molar ratios of 2:1 or 1:1 (MgCl2:CaCl2).

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IMPC 2020: XXX International Mineral Processing Congress, Cape Town, South Africa, 18-22 October 2020

The complementary tests showed it was possible to optimize the process by using a mass ratio of 1:6 (spodumene:chlorides) and molar ratio of 2:1 (MgCl2:CaCl2) during 30 minutes at roasting temperature of 1,150 °C, obtaining lithium extraction higher than 95%.

Acknowledgements

The authors would like to thank the geologist Dr. Reiner Neumann for his collaboration in the X-ray diffraction (XRD) studies. The authors also thank Cia Brasileira de Lítio for supplying the spodumene concentrate.

References

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Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Tarascon, J.M., 2012. Li–O2 and Li–S batteries with high energy storage. Nature Materials, 11, 19–29. Dessemond, C.; Lajoie-Leroux, F.; Soucy, G.; Laroreche, N.; Magnan, J.F., 2019. Spodumene: The Lithium Market, Resources and Processes. Minerals. 9(6), 334. El-Naggar, M.M.A.A.; Medina, L.F.; Espídola, A., 1988. The reaction between spodumene and tachyhydrite. Metallurgical Transactions B, 19B, 663-668. Li, H.; Eksteen, J.; Kuang, G., 2019. Recovery of lithium from mineral resources: State-of-the- art and perspectives – A review. Hydrometallurgy, v. 189, 105129. Medina, L.F.; El-Naggar, M. M. A. A., 1984. An alternative method for the recovery of lithium from spodumene. Metallurgical Transactions B, 15B (4), 725-726. Rosales, G.D.; Ruiz, M.D.C.; Rodriguez, M.H., 2014. Novel process for the extraction of lithium from -spodumene by leaching with HF. Hydrometallurgy. 147–148, 1–6. Fotouhi, A.; Auger, D. J., O’Neil, L. Cleaver, T.; Walus, S., 2017. Lithium-Sulfur Battery Technology Readiness and Applications—A Review. Energies. 10 (12), 1937.

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