Study on Electrochemical Behavior of Oxidized Pyrite in Alkaline Electrolyte

Abstract

Nowadays, refractory gold ore production around the world accounts for about 30% of total gold production, and the low leaching rate of such gold concentrate seriously limits the efficient utilization of gold resources. The alkaline preoxidation process can improve the leaching rate of this kind of gold deposit and has good development and application prospects. Therefore, it is of great significance to study the oxidation and dissolution behavior of pyrite in an alkaline environment. In this paper, the oxidation process of gold-bearing pyrite in an alkaline electrolyte was studied using electrochemical techniques, and the oxidation products of a pyrite electrode in an alkaline solution were characterized using XPS, SEM, and other analytical methods. The results show that the optimum pH for pyrite electrochemical oxidative dissolution is about 12, and the oxidation potential of pyrite should be above 0.8 V. In the process of alkaline oxidative dissolution of pyrite, part of the S element enters the electrolyte in the forms of Sx2−, S2O32−, SO32−, and SO42−, and a small amount of the S element is adsorbed on the surface of the electrode in the form of S0 and becomes a part of the passive layer. The Fe element is adsorbed on the surface of the electrode in the forms of Fe(OH)2, Fe2O3, and Fe2(SO4)3, which become the main components of the passivation layer. This study provides a theoretical basis and reference data for the chemical preoxidation treatment of gold-bearing sulfide ores.

Editorial for the Special Issue: “Valuable Metals Recovery by Mineral Processing and Hydrometallurgy”

“…Further study revealed the oxidation and dissolution behavior of pyrite in an alkaline environment, with the aim of facilitating Au exposure in the subsequent leaching [9]. The conclusion from the applied electrochemical testing techniques (cyclic voltammetry, linear scanning voltammetry, current-time, and electrochemical impedance spectroscopy), complemented with analytical methods such as XPS and SEM-EDS, is that the oxidative dissolution of pyrite occurs preferably in an alkaline environment with a pH of around 12, and an oxidation potential above 0.9 V (vs. SHE).…”