DECONTAMINATION OF TWO LIGAND-CONTAINING ELECTROPLATING SOLUTIONS ONE BY OTHER

摘要

The solid solutions of copper-(zinc)-potassium-ammonium diphosphates are precipitated after mixing rinsing wastewater containing copper diphosphate with rinsing wastewater containing acidic zinc (with ammonium) electroplating solution (case Ⅰ) or with spent etching solution of printed circuit boards (case Ⅱ) and pH adjustment. About 70-99.7% of environmentally dangerous substances, viz. copper, zinc and diphosphate ions are removed from the solution. Several possible ways to utilize the precipitate are suggested.Cu~(2+) and Zn~(2+) ions may be removed from the filtrates below DCL in industry using lime (case Ⅰ) or lime + CaCl_2 solution (case Ⅱ). After that, the diphosphate ions may be removed by addition of spent steel etching solution, or, alternatively, by continuous mixing with phosphogypsum. It is possible to remove Cu~(2+) and Zn~(2+) ions below DCL and to lower the concentration of phosphates (5 to 40 fold) and ammonium (95-99.7 %) by precipitation of barely soluble fine crystalline MgNH_4PO_4·6H_2O (struvite).