摘要
从LiFePO_(4)(简称LFP)废粉中回收有价元素已成为当下重要的研究方向之一。在此过程中,高效回收该废粉中的有价元素面临一个关键挑战,即如何在含铁、铝、磷的酸性溶液中深度去除Al^(3+),以便于后续制备电池级磷酸铁。本研究参考LFP废粉硫酸全浸液的成分,配置了Na_(2)SO_(4)-Li_(2)SO_(4)-Al_(2)(SO_(4))_(3)溶液,并利用冰晶石沉淀法脱除Al^(3+)。在对冰晶石沉淀除铝条件进行优化的基础上,深入阐明了多种类型冰晶石(如Na_(1.5)Li_(1.5)AlF_(6),Na_(2)LiAlF_(6)和Na_(3)AlF_(6))的形成规律,尤其明确了溶液初始Na/Li摩尔比和初始Al^(3+)浓度对冰晶石形成的影响机制,进而确定了各类冰晶石纯相的生成条件,为冰晶石沉淀法除铝提供了理论依据。将该方法应用于LFP废粉酸浸液中的Al^(3+)深度脱除研究,结果表明,冰晶石沉淀除铝的最佳条件为:F/Al摩尔比为6.6、初始pH值为2.5、反应温度为50℃、反应时间为2 h。在上述条件下,当初始Na/Li摩尔比为1.50或2.00时,沉铝产物为Na_(1.5)Li_(1.5)AlF_(6)冰晶石;当Na/Li摩尔比为3.00时,则形成Na_(3)AlF_(6)冰晶石。同时发现溶液中铁和磷的存在会抑制Na_(2)LiAlF_(6)的生成。利用冰晶石沉淀法,Al^(3+)质量浓度可从0.50 g/L降至20 mg/L以下,并能在低锂损的同时生成Na_(3)AlF_(6)冰晶石。本研究为LFP废粉湿法回收过程中Al^(3+)的低锂损深度选择性脱除提供了有效方法。
The recovery of valuable elements from spent LiFePO_(4)(LFP)black powder has become a significant research focus.A key challenge in the high-value recovery of this spent powder is the deep removal of aluminum(Al^(3+))from acidic solutions containing iron(Fe),aluminum(Al),and phosphorus(P)to produce battery-grade iron phosphate materials.In this study,the chemical composition of acidic leachates from sulfuric acid leaching of spent LFP powder was used as a reference,and Na_(2)SO_(4)-Li_(2)SO_(4)-Al_(2)(SO_(4))_(3) solutions were designed to optimize Al^(3+)removal via cryolite precipitation.Based on the optimization of the cryolite precipitation process for aluminum removal,the formation rules of various types of cryolite,including Na_(1.5)Li_(1.5)AlF_(6),Na_(2)LiAlF_(6),and Na_(3)AlF_(6),were clarified,with a particular focus on how the initial Na/Li molar ratio and Al^(3+)concentration in the solution affected the formation of cryolites.The conditions for generating pure phases of each cryolite were established,which provided practical guidance for Al^(3+)removal through cryolite precipitation.This method was applied to the deep removal of Al^(3+)from acidic leachates following the leaching of spent LFP powder.It was found that the optimal conditions for cryolite precipitation to remove aluminum were a F/Al molar ratio of 6.6,an initial pH of 2.5,a reaction temperature of 50℃,and a reaction time of 2 h.Under these conditions,when the initial Na/Li molar ratio was set at 1.50 or 2.00,the precipitated Al-bearing solid was Na_(1.5)Li_(1.5)AlF_(6) cryolite,while at a ratio of 3.00,Na_(3)AlF_(6) formed.The presence of iron and phosphorus in the solution hindered the formation of Na_(2)LiAlF_(6).Using cryolite precipitation,the concentration of Al^(3+)could be reduced from 0.50 g/L to less than 20 mg/L,with minimal lithium loss by forming Na_(3)AlF_(6).This research offers a viable solution for deep Al^(3+)removal from acidic leachates,ensuring minimal lithium loss during the hydrometallurgical recycling of spent LFP powder.
作者
罗枫
张盈
郑诗礼
张洋
王晓健
乔珊
Feng LUO;Ying ZHANG;Shili ZHENG;Yang ZHANG;Xiaojian WANG;Shan QIAO(Key Laboratory of Green Process and Engineering,National Engineering Research Center of Green Recycling for Strategic Metal Resources,Institute of Process Engineering,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《过程工程学报》
北大核心
2025年第11期1183-1194,共12页
The Chinese Journal of Process Engineering
基金
中国科学院战略性先导科技专项(编号:XDA0430105)。
关键词
磷酸铁锂废粉
冰晶石合成
冰晶石法除铝
废粉酸性浸出液
lithium iron phosphate waste powder
synthesis of cryolite
cryolite method for aluminum removal
acid leachate of waste powder
