Waste treatment of metal plating solutions

摘要

An efficient and economical process for the waste treatment of spent metal plating solutions, primarily spent electroless nickel solutions, to significantly reduce the metal content therein, so as to permit direct discharge to municipal water systems without violation of the law. The waste treatment process is a sequential two-step chemical precipitation process, whereby the dissolved metal content is precipitated first by sodium borohydride reduction, followed by sodium dimethyldithiocarbamate precipitation, with an intermediate filtration step and pH adjustment step interposed there between. The amount of metal-bearing sludge produced is minimal. Furthermore, the bulk of the metals in the sludge may be recovered and reused, resulting in significant reduction in hazardous waste disposal costs.