(1. 中南大學(xué) 冶金與環(huán)境學(xué)院，長沙 410083；
2. 中南大學(xué) 稀有金屬冶金與材料制備湖南省重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 針對高M(jìn)g和Li質(zhì)量比鹽湖鹵水提鋰難的問題，提出利用尖晶石LiMn2O4對鹽湖鹵水進(jìn)行選擇性提鋰，并在熱力學(xué)計(jì)算的基礎(chǔ)上繪制了298.15 K時(shí)Me(Li，Na，K，Mg)-Mn-H2O體系的φ—pH圖，討論尖晶石LiMn2O4脫Li+后所形成的λ-MnO2對鹽湖中Na+、K+、Mg2+與Li+的選擇性提取問題。結(jié)果表明：當(dāng)離子濃度為1 mmol/L，體系陰極極化電位降至0.79 V(vs SHE)時(shí)，λ-MnO2中Mn4+被還原為Mn3+，同時(shí)溶液中Li+由于“記憶效應(yīng)”而嵌入λ-MnO2晶格生成LiMn2O4；而極化電位需降至0.61、0.55和0.48 V時(shí)，才分別有Mg0.5Mn2O4、KMn2O4和 NaMn2O4生成，說明所選材料對Li+的選擇性優(yōu)于對Na+、K+和Mg2+的選擇性。此外，根據(jù)西臺(tái)吉乃爾鹽湖鹵水中主要組成陽離子濃度([Li]=30 mmol/L，[Na]=5 mol/L，[K]=0.2 mol/L，[Mg]=0.5 mol/L)繪制Me(Li，Na，K，Mg)-Mn-H2O系疊加φ—pH圖。熱力學(xué)研究表明：只需在鹵水原始pH條件下將體系的陰極極化電位調(diào)至 0.70 V＜φ＜0.87 V，λ-MnO2即可實(shí)現(xiàn)對Li+與大量Na+、Mg2+、K+的有效分離；將嵌Li+后的LiMn2O4通過調(diào)節(jié)電位極化至φ＞0.87 V，可實(shí)現(xiàn)Li+的脫附和富集。
關(guān)鍵字: Me-Mn-H2O系；LiMn2O4；熱力學(xué)；鹵水提鋰
（1. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
2. Hunan Key Laboratory for Metallurgy and Material Processing of Rare Metals,
Central South University, Changsha 410083, China）
Abstract:The spinel LiMn2O4 was chosen for extracting Li+ from brine with high mass ratio of Mg and Li. The corresponding φ—pH diagrams of Me (Li, Na, K, Mg)-Mn-H2O systems at 298.15 K were plotted and analyzed according to thermodynamic calculation when the concentration of Me (Li, Na, K, Mg) was set as 1 mmol/L. The results show that when the redox potential of Li-Mn-H2O system is controlled less than 0.79 V (vs SHE), Mn4+ in λ-MnO2 crystal structure can be reduced to Mn3+, meanwhile, Li+ in solution can be inserted into λ-MnO2 crystal lattice due to memory effect to form LiMn2O4. However, the redox potential for Mg0.5Mn2O4, KMn2O4 and NaMn2O4 is 0.61, 0.55 and 0.48 V, respectively. It indicates that Li+ is prior to be inserted into λ-MnO2 from solution under the same condition compared with Na+, K+ and Mg2+. In addition, based on the main cation compositions ([Li]=30 mmo/L, [Na]=5 mol/L, [K]=0.2 mol/L, [Mg]=0.5 mol/L) in West Taijnar Salt Lake brine, the φ—pH diagrams were overlapped. The thermodynamics analysis shows that, in natural brine, it is possible that Li+ can be extracted effectively using λ-MnO2 when the potential is controlled between 0.70 V and 0.87 V. After that, the formed LiMn2O4 can release Li+ when a voltage 0.87 V is applied. By this means, Li+ in brine can be extracted and concentrated.
Key words: Me-Mn-H2O system; LiMn2O4; thermodynamics; Li extraction from brine
