TREATMENT OF WASTEWATER FROM CYANIDE-FREE ZINC PLATING

Abstract

Wastewater from the electroplating process often contains high concentrations of heavy metals, and must be treated before being discharged into public sewage systems or natural recipients. In this research, rinsing wastewater after acid and alkaline zinc electroplating process was treated by the electrocoagulation process. The experiments were performed in a batch electrochemical reactor made of polypropylene with a volume of 250 cm³. During all treatments constant mixing was performed at a speed of 200 rpm. Different electrode pairs (anode-cathode) were used: Fe-Fe, Al-Al, Fe-stainless steel (SS), Fe-Cu, Al-SS, Al-Cu. The success of the electrocoagulation process, in terms of zinc removal from cyanide-free electroplating rinsing wastewater, achieved with electrode pairs was: Fe-SS > Fe-Cu > Fe-Fe, respectively. The initial concentration of zinc in the wastewater was 173.5 mg/L, and after 60 minutes of treatment with the Fe-SS electrode pair it was achieved removal efficiency of 99.8%, while the specific energy consumption was 6.10 kWh per mᶟ of treated wastewater, or 8.74 kWh per kg of removed zinc.