Influence and Countermeasures of Plating Chemicals on Zinc Wastewater Treatment

To comply with zinc effluent regulations, we investigated the influence of plating chemicals on zinc removal from zinc chloride solutions by coagulation with sodium hydroxide. Plating chemicals including ethylenediaminetetraacetic acid disodium salt（EDTA･2Na）, ammonium chloride, sodium citrate, triethanolamine（TEA）, sodium diphosphate, and potassium dihydrogen phosphate decrease zinc removal capabilities. The zinc removal capability in the solutions depends on the concentrations of additive compounds. Especially, the addition of EDTA･2Na and sodium diphosphate exert an important influence that is attributable to the complex forming reaction of zinc and EDTA･2Na. For the addition of 8.8 mg/L EDTA･2Na, removal of zinc from the solutions and exceeding the effluent regulation value of zinc was difficult. Furthermore, to reduce compounds interfering in wastewater, we examine emissions management. Results demonstrated that the drain of barrel processing increases the interfering compounds in wastewater. Plating chemicals disturb the zinc wastewater treatment.