Removal of metal ions from electroplating effluent by EDI process and recycle of purified water

In this paper, an improved configuration of the membrane stack was adopted in the electrodeionization (EDI) cell to prevent precipitation of bivalent metal hydroxide during the running. The operational parameters that influenced the electro-regeneration of cation exchange resins loaded with nickel ions were optimized, and the result showed that addition of a small amount of Na2SO4 into the electrode solution, moderate increase of applied voltage and initial metal ion concentration could get better regeneration effect. A steady and continuous process of electroplating wastewater treatment could be achieved with current efficiency of 33–38%, removal efficiency of at least 99.8% and enrichment factor of 22–36. Concentration of metal ions in purified water was 0.03–0.09 mg/L for nickel, 0.07–0.10 mg/L for copper, 0.06–0.15 mg/L for zinc, 0.07–0.10 mg/L for cadmium and 0.08–0.17 mg/L for chromium, respectively. This demonstrated the applicability of recovering heavy metals and purified water from electroplating effluent for industrial reuse.