Oxidative degradation of lignosulfonates during pressure leaching of zinc concentrates

This study investigates the effect of preliminary autoclave oxidation with molecular oxygen ( Т = 423 K, Р О ₂ = 0.6 MPa, τ = 2 h) on lignosulfonates differing in chemical composition and molecular weight distribution. Oxidation resulted in a reduction of hydroxyl groups and an increase in carbonyl groups, along with marked changes in solution properties such as redox potential, pH, specific conductivity, and surface tension at the liquid–gas interface. The functional activity of the initial and oxidized lignosulfonates was compared in terms of their ability to remove elemental sulfur films from the sphalerite surface under high-temperature oxidative pressure leaching conditions. The findings show that oxidative treatment decreases the effectiveness of lignosulfonates by diminishing their surface activity.