Extraction of Pb, Cu, Zn and As from Fine Dust of Copper Smelting Industry via Leaching with Sulfuric Acid

Fine dust from copper smelting plants is an important source of raw materials for the extraction of various valuable metals. A specific feature of dust from copper smelting plants in Kazakhstan is their high arsenic content of up to 15%. This work shows the possibility of hydrometallurgical processing of fine dust from copper smelters, obtained during the converting of copper mattes through the Vanyukov process, via direct leaching with sulfuric acid. The influence of temperature, process time and the S:L (solid/liquid) ratio on the selective extraction of Pb, Zn, Cu and As into targeted products under leaching conditions is studied. The results of the test work show that with the optimal process parameters of S:L = 1.5, t = 60 °C, τ = 60 min, the extraction of copper and zinc into solution is achieved as 89% and 96%, respectively, and lead into cake by up to 97%. The relatively low extraction of copper and zinc into the solution is explained by the transition of copper and zinc ferrites that are insoluble in sulfuric acid into the lead cake. The redistribution of arsenic between the leaching products established in this case also affects the reduction in copper and zinc in the solution. The extraction of arsenic into the solution is 49.32%. More than half of the arsenic from the dust is left in the lead cake. The concentration of arsenic in lead cake will lead to its transition into circulating dust during smelting. This will increase the accumulation of arsenic in the overall process flow. Therefore, when organizing dust-processing technology, it is necessary to provide measures for the preliminary removal of arsenic.