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196 P. Meshram et al. / Hydrometallurgy 150 (2014) 192–208 Table 5 Lithium extraction from its minerals/clays by alkali process. Raw material % Li Lepidolite 1.4 concentrate Zinnwaldite 1.4 concentrate Zinnwaldite 2.07% (tailing sample) Li2O Zinnwaldite 0.19 concentrate Zinnwaldite 1.21 concentrate Zinnwaldite 1.29 concentrate Montmorillonite 0.3–0.6 clay–hectorite Pre-treatment Experimental conditions % Li Li2CO3 extraction purity (%) 4:1; lime: defluor. lepidolite: 1 10:1 96 99 10:1 84 – 5:1 93 – 5:1 ~90 99.5 10:1 84 – –80 99 References Yan et al. (2012c) Jandová et al. (2009) Kondás and Jandová (2006) Jandová et al. (2010) Vu et al. (2013) Lien (1985), Crocker and Lien (1987) Roasting temp. (°C), time (h) Defluorination 860, 0.5 h Gypsum roast 950,1h Gypsum roast 1050 Roasting with 975 gypsum & Ca(OH)2 Roasting with CaCO3 825, 1 h Roasting with CaCO3 825 Roasting with 750 CaCO3 900 CaCO3–CaSO4 Water leaching Time (h) 1 0.167 0.5 1 1 4 – Temp. (°C) 150 90 85 90 90–95 95 RT (L/S ratio) 98.9 99.9 is obtained. Thus most of the alkaline processes involve either the heating of lithium minerals with alkali salts or in more advanced hydro- thermal processes by decomposition in solutions containing Na2CO3, NaOH, Na2SO4 and/or other alkali salts at elevated temperature and pressure. Ion-exchange processes are applied for the processing of the leach liquors obtained from spodumene, petalite and partly from zinnwaldite. Tables 4–6 summarize recent work on lithium extraction from its minerals and clays by using different approaches. 3.1.1. Acid process Sulfation roasting of lepidolite followed by water leaching was recently reported by Yan et al. (2012a). The lithium extraction effi- ciency of 91.6% could be achieved at a mass ratio of lepidolite/Na2SO4/ K2SO4/CaO of 1:0.5:0.1:0.1 and roasting at 850 °C (Table 4). Roasting at 880 °C with a mass ratio of lepidolite/Na2SO4/CaCl2 of 1:0.5:0.3 resulted in improved recovery (~95% Li) of lithium (Yan et al., 2012b). Above 99.5% pure lithium carbonate was obtained by evaporation and precipita- tion with Na2CO3. Luong et al. (2013) examined the sulfation roasting of a Korean lepidolite ore with sodium sulfate at 1000 °C, while achieving extraction of ~ 90.4% Li. Recently, the roasting of lepidolite with iron sul- fate at 850 °C and water leaching were investigated by Luong et al. (2014). Leaching of the calcines obtained from the open and closed sys- tems yielded leach liquors containing ~7.9 g/L Li and ~8.7 g/L Li, corre- sponding to the extraction of ~85% and ~93% Li, respectively. Lithium extraction (N90%) by roasting a low grade zinnwaldite concentrate (0.96% Li) with sodium sulfate followed by water leaching, was described by Siame and Pascoe (2011). A study by Sitando and Crouse (2012) showed the extraction of 97.3% Li (~5 g/L) by roasting a Zimbabwean petalite ore concentrate (4.1% Li2O) with concentrated sulfuric acid at 300 °C followed by water leaching at 50 °C. The leach liquor was evaporated till lithium was concentrated to N11 g/L and Li2CO3 of ~99% purity was precipitated by the addition of Na2CO3 at 95–100 °C. Amer (2008) reported the extraction of 90% Li from the Egyptian montmorillonite type clay containing lithium in 90 min of reaction in sulfuric acid at 250 °C. In order to process spodumene it is desired to convert α-spodumene to β-phase by roasting at 1070–1100 °C (Chen et al., 2011b; Clarke, 2013; Tahil, 2010). Tahil (2010) reported the roasting of spodumene in a kiln at ~1100 °C. The calcine was mixed with sulfuric acid and roasted at 250 °C and then leached in water to yield a solution of lithium sulfate. Reaction of β‐spodumene with H2SO4 is shown as reaction (2) (Mcketta, 1988): Li2O⋅Al2O3⋅4SiO2ðsÞ þ H2SO4ðconcÞ→Li2SO4ðsÞ þ Al2O3⋅4SiO2ðsÞ þ H2OðgÞ: ð2Þ Lithium carbonate can be recovered by the addition of sodium carbon- ate to the solution after pH adjustment, purification and evaporation (Reaction (3)). Li2SO4ðaqÞ þ Na2CO3ðaqÞ→Li2CO3ðsÞ þ Na2SO4ðaqÞ: ð3Þ The world's first continuous plant to convert spodumene concentrate to lithium carbonate by calcination, roasting of calcine with H2SO4 and water leaching, was commissioned in 2012 by Galaxy Resources in China (Clarke, 2013). One of the drawbacks of the sulfuric acid method to treat lepidolite, petalite and zinnwaldite is the requirement of a high concentration of acid and complex purification processes, whereas spodumene needs to be converted to the more leachable β‐phase at higher temperature. Table 6 Lithium extraction from its minerals/clays by chlorination process. Raw material Lepidolite Spodumene (3.58% Li) Lepidolite concentrate (2.0% Li) Spodumene (7.2% Li2O) Lepidolite ore (3.70% Li2O) Experimental conditions Roasting temp. (°C) 935 1000 880 1100 With CaCO3 + CaCl2, 950 Time (h) Leaching L/S ratio Temp. (°C) 80 80 60 – 90 Time (h) 1 1 0.5 – 1 % Li extraction Product ~ 100 LiCl 58 LiCl 92.8 Li2CO3 100 LiCl 80.0 LiCl References Löf and Lewis (1942) Peterson and Gloss (1959) Yan et al. (2012d) Barbosa et al. (2014) Vyas et al. (1975) 13 4 0.5 2.5 5 – 10:1 2.5:1 – 10:1PDF Image | Extraction of lithium from primary and secondary sources
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