以废旧锂离子电池为原料制备棒状草酸钴粉末

Preparation of rod-like cobalt oxalate powder from spent lithium-ion batteries

研究从废旧锂离子电池中回收钴并制备棒状草酸钴粉末的工艺。研究结果表明：该工艺采用H2SO4＋Na2S2O3为浸出剂对正极材料浸出,在最优条件即液固比为10：1,H2SO4浓度为2.0 mol/L,Na2S2O3浓度为0.15 mol/L,温度为85℃,浸出时间为120 min时,钴的浸出率达96.5%。浸出液中加入碳酸氢铵调节pH至5.0以除出浸出液中的铝和铜,不经过滤操作直接使用次氯酸钠氧化沉淀铁和锰离子,过滤后滤液中仅含铁0.006 g/L,锰0.004 g/L,而钴的损失率仅为1.2%。滤液使用P507萃取分离钴和镍、锂,在相比为1.5：1.0,平衡pH为4.5,P507的体积分数为25%的条件下,经二级逆流萃取后钴的萃取率为99.4%。使用180 g/L的硫酸为反萃剂,相比为4~5时,钴的回收率达99.9%。反萃液使用草酸铵沉钴,沉钴的最优条件为50℃,终点pH为1.5,C2O42与Co2＋摩尔比n（C2O42）：n（Co2＋）=1.15：1。经SEM分析,沉淀而得的钴产品为形貌良好的棒状草酸钴。整个流程方法简便,废旧锂离子电池中钴回收率达到95%,草酸钴中钴含量达31.1%,符合工业要求。

A process for the recovery of cobalt and preparation of rod-like cobalt oxalate from the cathode active materials of the lithium-ion secondary batteries was presented. The results show that leaching efficiency of 96.5% of Co can be achieved under optimum conditions of liquid/solid ratio 10：1, 2 mol/L H2SO4, 0.15 mol/L Na2S203, with leaching time 120 min at 85 ℃. The removal of A13＋ and Cu2＋ from the leach liquor can be achieved by adding ammonium bicarbonate and adjusting the pH to 5.0, and the oxidative precipitation of Fe2＋ and Mn2＋ was carried out by adding sodium hypochlorite. In this process, the loss of cobalt is not beyond 2% （mass fraction）. In subsequent solvent extraction study, 99.4% of the cobalt is recovered with a two-stage counter-current extraction using 25% saponified P507 as an extractant at an O/A ratio of 1.5 and at equilibrium pH 4.5, the stripping rate of cobalt is 99.9% at O/A ratio of 4-5 with 180 g/L sulfuric acid solution. Finally, cobalt was chemically deposited as oxalate from the strip liquor. Experimental results show that the optimum cobalt oxalate precipitation conditions are temperation 50 ℃, terminal pH 1.5, n（C2On2-）：n（Co2＋）=1.15：1. Overall, this hydrometallurgical process is simple, 96.5% cobalt can be recovered from the spent lithium-ion batteries, and 31.1% （mass fraction） of cobalt is pound in cobalt oxalate.