Selective Ozone-Assisted Acid Leaching of Copper from Copper Smelter Slag by Using Isopropanol as a Solvent

Abstract

Copper content in copper smelter slag exceeds that in copper ores, which has attracted increasing interest to recover copper from this by-product of pyrometallurgical copper production. The isopropanol-sulfuric acid-ozone system has been tested under different conditions to extract this metal from copper smelter slag containing chalcopyrite as a copper mineral. Isopropanol as a solvent played a key role in increasing the copper recovery to 87% after 5 h of leaching, while the use of an aqueous solution of sulfuric acid allowed only 13% of copper to be recovered. Iron extraction under these conditions was only 10%. The role of ozone was spectroscopically proven to oxidize ferrous ions to form ferric ions, which are effective oxidizers of chalcopyrite. The presence of copper in solution in the form of cuprous (Cu+) ions was proven electrochemically. The increased copper extraction in the solution was caused by the stabilization of cuprous ions by isopropanol. The limiting stage of the process was the chemical reaction on the chalcopyrite surface with the activation energy of 73.4 kJ mol−1.