Study on pre-oxidation of silver concentrate and leaching behaviour of Zn, Cu and In during oxygen-pressure leaching

Given the limitations of current processing methods and the potential of high recovery of silver as a flotation concentrate, this study proposes a pre-oxidation followed by oxygen pressure sulphuric acid leaching route for zinc, copper and indium and thoroughly examines the alteration in micro-morphology of the silver concentrate of 1.22% Pb, 3010 g/t Ag and 649 g/t In. Under the optimal conditions of a sulphuric acid pre-oxidation temperature of 60 °C, and an acid-to-ore mass ratio of 0.6, over 15 h, the PO and -OH polar groups of flotation reagents on the surface of silver concentrate particles are effectively neutralized through sulphuric acid oxidation. This action prevents the formation of a hydration film and mineral inclusions, thereby facilitating the efficient leaching of valuable elements. With a set reaction temperature of 155 °C, an initial acidity of 160 g/L, a reaction time of 180 min, an oxygen partial pressure of 0.8 MPa and a liquid-to-solid ratio of 7 mL/g, the leaching efficiency of Zn, Cu and In in the silver concentrate reach 94.8%, 98.4% and 91.1%, respectively while the lead and silver grades in the leach residue increase to 2.88% and 7754 g/t, respectively.