磷酸铁离子筛卤水提锂热力学分析
来源期刊：中国有色金属学报2013年第2期
论文作者：赵中伟 梁新星 刘旭恒 何利华 陈星宇 司秀芬 陈爱良
文章页码：559 - 568
关键词：Me-Fe-P-H2O系；FePO4离子筛；热力学；提锂；卤水
Key words：Me-Fe-P-H2O system; FePO4 ion-sieve; thermodynamics; Li extraction; brine
摘 要：针对高Mg和Li质量比盐湖卤水提锂困难的问题，提出利用LiFePO4/FePO4材料对盐湖卤水进行选择性提锂的思路。在热力学计算的基础上绘制298.15 K时Me(Li, Na, K, Mg)-Fe-P-H2O体系的j—pH图，并讨论FePO4对盐湖中Na+、K+、Mg2+与Li+的选择性吸附问题。结果表明：当离子浓度为0.1 mol/L、体系氧化还原电位降到0.36 V(vs SCE)时，FePO4中+3价的铁即被还原为+2价，同时Li+嵌入FePO4晶格生成LiFePO4；而体系电位需降到0.132 V和0.073 V才分别生成KFePO4和NaFePO4，说明材料对Li的选择性优于Na和K的，而Mg0.5FePO4则在计算分析的范围内不能稳定存在，说明FePO4对Mg2+无吸附性。因而，在适当的电位范围内(本研究的计算条件下为0.173~0.33 V)即可利用磷酸铁材料实现Li与Na、K、Mg等元素的选择性提取，而吸附锂后通过调节氧化还原电位大于约0.33 V，即可实现LiFePO4材料中Li的脱出。
Abstract: LiFePO4/FePO4 material was chosen as ion-sieve for selectively extracting Li from high Mg/Li mass ratio brine. Thermodynamic analysis was conducted about selectivity of adsorption of Na+, K+, Mg2+ and Li+ by FePO4 ion-sieve. The corresponding j-pH diagrams of Me (Li, Na, K, Mg)-Fe-P-H2O system at 298.15K were plotted and analyzed. The results show that, under the condition of ion concentration 0.1 mol/L, the redox potential of Me (Li, Na, K, Mg)-Fe-P-H2O system is controlled not higher than 0.36V (vs SCE), Fe3+ in FePO4 is reduced to Fe2+, and, Li+ is inserted into FePO4 crystal lattice to form LiFePO4 synchronously. KFePO4 and NaFePO4 will not be obtained until the potential of the system is reduced to 0.132 V and 0.073 V, respectively. Li+ is absorbed preferentially compared with Na+ and K+ by FePO4 ion-sieve. Mg0.5FePO4 can’t exist steadily in the studied range, which means that Mg2+ can’t be absorbed by the material. Therefore, the FePO4 ion-sieve can be used to selectively extract Li+ when the redox potential being set within 0.173~0.33 V. After extraction, Li can be de-intercalated from LiFePO4 by setting the potential of system above 0.33 V.
赵中伟，梁新星，刘旭恒，何利华，陈星宇，司秀芬，陈爱良
(中南大学 冶金科学与工程学院，长沙 410083)
摘 要：针对高Mg和Li质量比盐湖卤水提锂困难的问题，提出利用LiFePO4/FePO4材料对盐湖卤水进行选择性提锂的思路。在热力学计算的基础上绘制298.15 K时Me(Li, Na, K, Mg)-Fe-P-H2O体系的j—pH图，并讨论FePO4对盐湖中Na+、K+、Mg2+与Li+的选择性吸附问题。结果表明：当离子浓度为0.1 mol/L、体系氧化还原电位降到0.36 V(vs SCE)时，FePO4中+3价的铁即被还原为+2价，同时Li+嵌入FePO4晶格生成LiFePO4；而体系电位需降到0.132 V和0.073 V才分别生成KFePO4和NaFePO4，说明材料对Li的选择性优于Na和K的，而Mg0.5FePO4则在计算分析的范围内不能稳定存在，说明FePO4对Mg2+无吸附性。因而，在适当的电位范围内(本研究的计算条件下为0.173~0.33 V)即可利用磷酸铁材料实现Li与Na、K、Mg等元素的选择性提取，而吸附锂后通过调节氧化还原电位大于约0.33 V，即可实现LiFePO4材料中Li的脱出。
关键词：Me-Fe-P-H2O系；FePO4离子筛；热力学；提锂；卤水
ZHAO Zhong-wei, LIANG Xin-xing, LIU Xu-heng, HE Li-hua, CHEN Xing-yu, SI Xiu-fen, CHEN Ai-liang
(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)
Abstract:LiFePO4/FePO4 material was chosen as ion-sieve for selectively extracting Li from high Mg/Li mass ratio brine. Thermodynamic analysis was conducted about selectivity of adsorption of Na+, K+, Mg2+ and Li+ by FePO4 ion-sieve. The corresponding j-pH diagrams of Me (Li, Na, K, Mg)-Fe-P-H2O system at 298.15K were plotted and analyzed. The results show that, under the condition of ion concentration 0.1 mol/L, the redox potential of Me (Li, Na, K, Mg)-Fe-P-H2O system is controlled not higher than 0.36V (vs SCE), Fe3+ in FePO4 is reduced to Fe2+, and, Li+ is inserted into FePO4 crystal lattice to form LiFePO4 synchronously. KFePO4 and NaFePO4 will not be obtained until the potential of the system is reduced to 0.132 V and 0.073 V, respectively. Li+ is absorbed preferentially compared with Na+ and K+ by FePO4 ion-sieve. Mg0.5FePO4 can’t exist steadily in the studied range, which means that Mg2+ can’t be absorbed by the material. Therefore, the FePO4 ion-sieve can be used to selectively extract Li+ when the redox potential being set within 0.173~0.33 V. After extraction, Li can be de-intercalated from LiFePO4 by setting the potential of system above 0.33 V.
Key words:Me-Fe-P-H2O system; FePO4 ion-sieve; thermodynamics; Li extraction; brine
