Simultaneous decontamination of two copper ligand-containing solutions by mixing and precipitation

Simultaneous decontamination of different metal waste streams has potential advantages over treating the streams separately. Mixing copper diphosphate electroplating rinsing bath solutions with spent etching solution of printed circuit boards and adjusting pH with H2SO4 results in cost-effective removal of environmentally dangerous substances. Copper and diphosphate ions are 99.7% and 71%, respectively, removed, from the solution by precipitation of solid solutions of copper-potassium-ammonium-diphosphate salts. The final decontamination of the resultant solution depends on the wastewater composition from the specific plant and the environment protection requirements. Copper (II) ions may be removed below DCL in industry using lime and CaCl2. The concentration of diphosphate ions may be drastically reduced (by factor of ∼ 1000) by either interaction with a spent steel etching solution or by continuous mixing with phosphogypsum. Copper (II) ions may be removed below DCL and the concentrations of phosphates and ammonium may be lowered by factors of 10 to 20 and 400 to 1200, respectively, by precipitation of barely soluble fine crystalline MgNH4PO46H2O using phosphoric acid and MgO. Several possible ways to utilize the precipitate have been proposed.