盐析-冷冻芒硝法处理废旧锂电池电解液废水的研究

Study on theTreatment of Waste Lithium Battery Electrolyte Wastewater by Salting-out-frozen Mirabilite Method

采用Na_(2)SO_(4)盐析法来分离并回收废水中碳酸酯类的电解液溶剂,降低废水COD。再通过冷冻芒硝法回收硫酸钠盐,同时实现处理废水的循环回用。考察了Na_(2)SO_(4)投加量、盐析温度、pH、冷冻温度等对废水COD去除效果的影响。结果表明,常温下Na_(2)SO_(4)质量分数为30%,pH为3.0时,COD去除率最高可达71.39%;冷冻回收芒硝的最佳温度为5℃,60.53%的Na_(2)SO_(4)可被回收;芒硝盐析多次循环回用废水的COD去除率可稳定在60%以上;此外,盐析废水分液得到的上层有机相中含有36.18%的碳酸二乙酯,24.82%碳酸乙烯酯和33.79%的碳酸丙烯酯,可进行回收利用。该方法处理的工艺废水和回收的芒硝均可循环回用,且处理效果较好,是一种经济、高效的废旧锂电池回收工艺有机废水处理方法。

Na_(2)SO_(4) salting-out was applied to separate and recycle the organic carbonate electrolyte solvent in the wastewater and reduce COD.And then sodium sulfate in the solution was recycled by frozen mirabilite method with the realization of zero-discharge recycling for the wastewater.Reaction conditions such as dosage of Na_(2)SO_(4),salting-out temperature,pH,freezing temperature affecting the removal of COD in simulated wastewater were investigated.The results show that when the Na_(2)SO_(4) dosage is 30%and the pH is 3.0 at room temperature,the highest COD removal is 71.39%;the optimum temperature for freezing recovery of mirabilite is 5℃,and the corresponding recovery is 60.53%;the COD removal of the reused wastewater after multiple salting-out cycles of mirabilite can keep stable at more than 60%;Moreover,the recycled organic solvent consists of 36.18%diethyl carbonate,24.82%ethylene carbonate and 33.79%propylene carbonate.In this study,the wastewater and the Na_(2)SO_(4) can be recycled and the applied method is an economical,environmentally friendly and efficient organic wastewater treatment for the recycling process of waste lithium batteries.