硝酸型废退锡水的分离特性与蒸馏强化偏锡酸回收

Separation characteristics of nitric acid type tin stripping waste solution and distillation enhanced recovery of meta stannic acid

针对电路板硝酸型废退锡液再生和锡提取技术的改进,对硝酸型废退锡水的物理化学特征、氧化还原与沉淀反应规律、真空蒸馏特性进行了理论分析和实验研究。结果表明:硝酸溶液中三价铁离子的存在可以将锡离子氧化为四价;硝酸浓度的提高可促进β型偏锡酸沉淀的形成;蒸馏是硝酸的浓缩过程,当水的蒸出率达到67.75%时,硝酸质量分数提高到40.04%,锡的质量分数降到了0.04%。废退锡水中锡以β型偏锡酸形式析出,析出率达到97.36%。经过蒸馏强化所获得沉淀物具有更好的沉淀特性;蒸馏底液保留了退锡水的有效成分,可作为再生退锡水。

Aiming at the improvements of regeneration technology and tin extraction mothed of nitric acid type tin stripping waste solution for PCB industries,the physical and chemical characteristics,the behaviors of redox and precipitation reac⁃tions,and vacuum distillation characteristics of waste tin stripping solution were theoretically analyzed and experimentally studied.The results showed that Fe^(3+)in nitric acid solution could oxidize tin ion to tetravalent.The increase of nitric acid con⁃centration promoted the precipitation formation ofβ-type meta stannic acid.Vacuum distillation was the concentration pro⁃cess of nitric acid.When the evaporation rate of water reached 67.75%,the mass ratio of nitric acid increased to 40.04%and the mass ratio of tin decreased to 0.04%.Tin in the waste tin stripping water was precipitated in the form ofβ-metastannic acid,and the precipitation rate reached 97.36%.The precipitateβ-metastannic acid obtained by distillation had better pre⁃cipitation characteristics.The distillation bottom liquid retained the effective components of tin stripping liquid and could be used to mix tin stripping liquid.