离子交换与吸附

作为影响电容器性能的关键材料，化成箔在腐蚀工段会产生大量含有Al³⁺的硝酸废液，直接排放会导致资源浪费和严重的环境污染。针对硝酸废液中Al³⁺回收率不高、残液体积大的问题，采用多级“扩散渗析+电渗析”的离子膜集成工艺资源化回收铝箔腐蚀废酸液。研究了进水进料流量、实验时间对扩散渗析工段和电渗析工段中回收酸浓度、酸回收率和Al³⁺截留率的影响。实验证明，在扩散渗析工段，酸回收浓度和酸回收率随着进水进料流量增大而降低，Al³⁺截留率随着进水进料流量增大而提高；在电渗析工段，随着实验进行，硝酸回收率迅速升高，平均电流效率和Al³⁺截留率呈下降趋势。经过“扩散渗析+电渗析”多级处理工艺后，99.2%的硝酸被回收利用，83.6%的硝酸铝被截留作为副产品出售，回收的低电导率淡化水和蒸发水用于铝箔清洗工段、接收水，实现了化成箔废液高效分离回收、工业水循环使用和含氮废水近零排放，为膜集成工艺在铝箔化成废酸处理中的规模化应用奠定了基础。

Formed foil is the primary raw material for aluminum electrolytic capacitors. During the forming process of aluminum foil, a large amount of etching wastewater containing nitric acid and Al³⁺ is generated. This wastewater discharge results in, the release of nitrate into sewage disposal systems, leading to serious environmental pollution. To address the challenges posed by low recovery rates and large volumes of etching wastewater, a project was undertaken to achieve zero discharge and cyclic utilization of nitrates from aluminum foil etching wastewater, employing a combination of multiple diffusion dialysis and electrodialysis. The project investigated the effects of flow rate and reaction time on the recovered acid concentration, acid recovery ratio, and Al³⁺ rejection ratio. The results revealed that in the process of diffusion dialysis, the recovered acid concentration and acid recovery ratio decreased with an increase in flow rate, while the Al³⁺ concentration increased. Conversely, in the process of electrodialysis, an increase in reaction time led to higher acid recovery ratios, reduced Al³⁺ rejection coefficients, and improved average current efficiency. As a result of these processes, 99.2% of the HNO₃ was reused in the production of aluminum foil, while 83.6% of Al(NO₃)₃ was obtained as a by-product. Moreover, desalinated water from electrodialysis was recycled as cleaning water and receiving water in the purification process. This innovative approach not only offers a solution for achieving zero discharge of aluminum foil etching wastewater but also pave the way for the widespread implementation of membrane-integrated processes in the treatment of such wastewater on a large scale.