(中南大學(xué) 冶金科學(xué)與工程學(xué)院，長(zhǎng)沙 410083)
摘 要: 針對(duì)高M(jìn)g和Li質(zhì)量比鹽湖鹵水提鋰?yán)щy的問(wèn)題，提出利用LiFePO4/FePO4材料對(duì)鹽湖鹵水進(jìn)行選擇性提鋰的思路。在熱力學(xué)計(jì)算的基礎(chǔ)上繪制298.15 K時(shí)Me(Li, Na, K, Mg)-Fe-P-H2O體系的j—pH圖，并討論FePO4對(duì)鹽湖中Na+、K+、Mg2+與Li+的選擇性吸附問(wèn)題。結(jié)果表明：當(dāng)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(shí)，F(xiàn)ePO4中+3價(jià)的鐵即被還原為+2價(jià)，同時(shí)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(shuō)明材料對(duì)Li的選擇性優(yōu)于Na和K的，而Mg0.5FePO4則在計(jì)算分析的范圍內(nèi)不能穩(wěn)定存在，說(shuō)明FePO4對(duì)Mg2+無(wú)吸附性。因而，在適當(dāng)?shù)碾娢环秶鷥?nèi)(本研究的計(jì)算條件下為0.173~0.33 V)即可利用磷酸鐵材料實(shí)現(xiàn)Li與Na、K、Mg等元素的選擇性提取，而吸附鋰后通過(guò)調(diào)節(jié)氧化還原電位大于約0.33 V，即可實(shí)現(xiàn)LiFePO4材料中Li的脫出。
關(guān)鍵字: Me-Fe-P-H2O系；FePO4離子篩；熱力學(xué)；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
