磷酸锂渣制备电池级碳酸锂工艺研究

磷酸锂渣作为低浓度含锂废液的回收产物,因杂质含量高难以直接作为锂电池的生产原料。为充分利用该类磷酸锂渣,以缓解新能源汽车产业的快速发展对锂资源的需求压力,依据锂盐与钙盐在弱酸性条件下具有较大的溶解性差异,向磷酸锂中添加一定量酸和易溶性钙盐,在酸性条件下直接实现磷酸锂渣中锂与磷的分离。实验研究了酸加入量、钙加入量、转化终点pH、转化液固比及转化时间对锂转化效率的影响,发现在酸加入量与固体原料的体积质量比为1.04 mL/g、钙加入量为磷酸锂中磷物质的量的0.9倍、回调pH终点为4.0条件下,锂的转化率可达96.8%。转化液经调节pH除杂、离子交换深度除杂,控制完成液的锂浓度、碳酸钠过滤精度、反应体系温度等,可制备出电池级碳酸锂。碳酸锂产品主成分质量分数约为99.65%,产品质量符合YS/T 582—2013《电池级碳酸锂》的要求,锂的综合回收率达到93.4%。

Study on preparation process of battery-grade lithium carbonate from slag containing lithium phosphate

The slag containing lithium phosphate as the recovery product of low concentration lithium containing waste liquid is hardly used as the production raw material of lithium battery due to its high impurity content.In order to make full use of this kind of lithium phosphate slag to alleviate the demand pressure of lithium resources for the rapid development of new energy vehicle industry,according to the large solubility difference between lithium salt and calcium salt under weak acid conditions,acid and soluble calcium salt were added to lithium phosphate to directly realize separation of lithium and phosphorus from lithium phosphate slag under acidic conditions.The effect of acid addition amount,calcium addition amount,p H of conversion end point,conversion liquid-solid ratio and conversion time on lithium conversion efficiency was studied.It was found that the conversion rate of lithium could reach 96.8% when the volume mass ratio of acid addition amount to solid raw material was 1.04 mL/g,calcium addition amount was 0.9 times of the amount of phosphorus in lithium phosphate and the pH end point was 4.0.After pH adjustment,chemical impurity removal and ion exchange depth removal of the converted liquid,battery grade lithium carbonate could be prepared by strictly controlling the lithium concentration in the purified liquid,the filtration accuracy of sodium carbonate,the temperature of the reaction system.The product contained the main component of about 99.65%,with the impurity content up to the requirements of YS/T 582—2013.The comprehensive recovery of lithium was 93.4%.