(中南大學 冶金科學與工程學院，長沙 410083)
摘 要: 針對高Mg和Li質(zhì)量比鹽湖鹵水提鋰困難的問題，提出利用LiFePO4/FePO4材料對鹽湖鹵水進行選擇性提鋰的思路。在熱力學計算的基礎上繪制298.15 K時Me(Li, Na, K, Mg)-Fe-P-H2O體系的j—pH圖，并討論FePO4對鹽湖中Na+、K+、Mg2+與Li+的選擇性吸附問題。結(jié)果表明：當離子濃度為0.1 mol/L、體系氧化還原電位降到0.36 V(vs SCE)時，F(xiàn)ePO4中+3價的鐵即被還原為+2價，同時Li+嵌入FePO4晶格生成LiFePO4；而體系電位需降到0.132 V和0.073 V才分別生成KFePO4和NaFePO4，說明材料對Li的選擇性優(yōu)于Na和K的，而Mg0.5FePO4則在計算分析的范圍內(nèi)不能穩(wěn)定存在，說明FePO4對Mg2+無吸附性。因而，在適當?shù)碾娢环秶鷥?nèi)(本研究的計算條件下為0.173~0.33 V)即可利用磷酸鐵材料實現(xiàn)Li與Na、K、Mg等元素的選擇性提取，而吸附鋰后通過調(diào)節(jié)氧化還原電位大于約0.33 V，即可實現(xiàn)LiFePO4材料中Li的脫出。
關鍵字: Me-Fe-P-H2O系；FePO4離子篩；熱力學；提鋰；鹵水
（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
