尖晶石锰酸锂卤水提锂热力学

来源期刊:中国有色金属学报2013年第12期

论文作者:司秀芬 张伟光 何利华 梁新星 赵中伟

文章页码:3410 - 3423

关键词:Me-Mn-H2O系;LiMn2O4;热力学;卤水提锂

Key words:Me-Mn-H2O system; LiMn2O4; thermodynamics; Li extraction from brine

摘    要:针对高Mg和Li质量比盐湖卤水提锂难的问题,提出利用尖晶石LiMn2O4对盐湖卤水进行选择性提锂,并在热力学计算的基础上绘制了298.15 K时Me(Li,Na,K,Mg)-Mn-H2O体系的φ—pH图,讨论尖晶石LiMn2O4脱Li+后所形成的λ-MnO2对盐湖中Na+、K+、Mg2+与Li+的选择性提取问题。结果表明:当离子浓度为1 mmol/L,体系阴极极化电位降至0.79 V(vs SHE)时,λ-MnO2中Mn4+被还原为Mn3+,同时溶液中Li+由于“记忆效应”而嵌入λ-MnO2晶格生成LiMn2O4;而极化电位需降至0.61、0.55和0.48 V时,才分别有Mg0.5Mn2O4、KMn2O4和 NaMn2O4生成,说明所选材料对Li+的选择性优于对Na+、K+和Mg2+的选择性。此外,根据西台吉乃尔盐湖卤水中主要组成阳离子浓度([Li]=30 mmol/L,[Na]=5 mol/L,[K]=0.2 mol/L,[Mg]=0.5 mol/L)绘制Me(Li,Na,K,Mg)-Mn-H2O系叠加φ—pH图。热力学研究表明:只需在卤水原始pH条件下将体系的阴极极化电位调至 0.70 V<φ<0.87 V,λ-MnO2即可实现对Li+与大量Na+、Mg2+、K+的有效分离;将嵌Li+后的LiMn2O4通过调节电位极化至φ>0.87 V,可实现Li+的脱附和富集。

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.

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