Separation and Recovery of Gold, Copper and Silver from Waste Acid Residues by Novel Alkaline Dechlorization-Acid Leaching Process

摘要

A new process involving alkaline dechlorination and acidic leaching is developed for separation and recovery of valuable metals (such as copper, gold and silver) from waste acid residues containing 20.5 % sulfur and 3.198 % chlorine. It is shown that under the conditions of the liquid/solid ratio of 6:1 mL/g, leaching time of 1.5 h, pH 7-14, alkaline washing can effectively remove copper chloride from waste acid residues, favoring the subsequent operations for leaching and recovery of metals. The leaching rate of copper reaches 91.54 % and more than 99.8 % of gold and silver are enriched in the slag for further recovery when the alkaline washed waste acid residues are subjected to the following leaching conditions: L/S ratio of 6:1 mL/g, concentration of the mixed acid consisting of reagent A of 1.24 mol/L and reagent B of 0.3 mol/L, temperature of 85 °C and leaching time of 1.5 h. The process is thus very promising for efficient separation and high recovery of copper, gold and silver from waste acid residues.