Recovery Of Valuable Metals From Sludge In Electroplating Wastewater

A Shaanxi electroplating factory’s plating wastewater containing Cu, Zn, Ni, Fe,Ag metals and get electroplating wastewater sludge that gathered by divalent sulfur acidtype chelating resin （DTCR）. Sludge contains valuable metal and it will bring greatharm once into the environment if it’s not being treated. This paper carried out valuablemetal recovery process in sludge.Research shows with dry, leaching, recovery and separation process can beeffectively separated electroplating wastewater sludge in Cu, Ni, Zn, Fe and Ag metals.Leaching well in1h under400℃and its valuable metals exist in the form of metaloxides and sulfates. Under the conditions of concentration of sulfuric acid by25%,liquid-solid ratio is3:1for1h; the metal leaching rates were obtained: Cu98.62%, Zn93.84%, Ni76.46%, Fe88.06%. Study on kinetics of leaching showed that copperleaching of the activation energy is43.14KJ mol^-1, leaching process is underdynamics control. Chlorinated Roasting-Ammonia leaching-hydrazine hydratereduction of silver recovery rate is96.36%. Iron removal rate is99.25%under thecondition of pH=3.2, hydrogen peroxide H₂O₂/Fe²⁺（mass percentage） for0.6; Copperreduction rate was over99.57%at room temperature, with390rpm stirring speed andthe amount of zinc is of1.2times in theory within15min of the reduction; At atemperature of80℃, the dosage of Sb₂O₃in50mg/L, the amount of zinc is4times astheoretical content, pH=4.0in1h, reduced zinc powder by nickel and its rate is up to99.25%. After experiment, electroplating wastewater sludge’s drying, oxidize roasting, sulfuric acid leaching and zinc powder reduction process is feasible. The recovery rateof Cu, Ni, Zn, Fe and Ag metals is up to94.59%,85.14%,95.02%,94.99%and96.36%respectively.