废退锡液回收技术的应用研究

Application study on reclaiming technology of spent tin-stripping solution

采用絮凝和减压蒸馏相结合的方法从废退锡液中分离出二氧化锡、硝酸、硝酸铜和硝酸铁。对各工序的工艺条件进行优化,以提高回收产品的回收率和品质。介绍了该工艺的拓展工艺路线。采用聚丙烯酰胺（PAM）质量分数为1.5%的溶液,按其与废退锡液体积比为1∶20处理废退锡液时,絮凝效果最佳。絮凝后宜在80-90°C范围内将絮凝的废退锡液陈化12 h以上再抽滤。滤渣通过3次洗涤后,80°C预烘0.5 h＋300°C烘烤3.5 h,可回收得到纯度高达95.41%的SnO2。硝酸由滤液经80-90°C减压分馏回收得到。取蒸馏余液进行冷却结晶,即可分离得到硝酸铁和硝酸铜。本工艺能把废退锡液的所有组分分离,为废退锡液回用提供技术支持,减少环境污染。

SnO2, HNO3, Cu（NO3）2 and Fe（NO3）3 were separated from spent tin-stripping solution by flocculation and vacuum distillation. The process conditions of each procedure were optimized to improve recovery and quality of the products reclaimed. The process route expanded based on the given process was introduced. The flocculation efficiency of spent tin-stripping solution is the best by using a flocculent containing 1.5wt% polyacrylamide （PAM） when the volume ratio of flocculent to spent tin-stripping solution is 1：20. It is appropriate for the flocculated spent tin-stripping solution to be aged for more than 12 h at 80-90 ℃ before being filtered by suction. SnO2 with a purity up to 95.41% is reclaimed from filter cake through washing for 3 times followed by prebaking at 80 ℃ for 0.5 h plus baking at 300℃ for 3.5 h. HNO3 is reclaimed from filtrate by vacuum distillation at 80-90℃. Cu（NO3）2 and Fe（NO3）3 are reclaimed by cooling down the remaining solution from vacuum distillation. All of the components in spent tin-stripping solution can be separated using the given process, which provides a technical support for reclaiming spent tin-stripping solution, reducing environmental pollution.