Behavior of Surface-Active Substances in a Nitric Acid Medium and Prospects for Using Them in Hydrometallurgy

The behavior of surface-active substances (surfactants) is studied using the examples of lignosulfonate (LS) and sodium dodecyl sulfate (SDS) in aqueous and nitric acid media as promising additives for the nitric acid leaching of refractory ore concentrates. The effect the temperature (15–70°С) and concentrations of the surfactant ( C surfactant = 0.02–200 g/dm 3 ) and nitric acid ( C_HNO_3 = 0.1–10 g/dm 3 ) have on the surface tension, critical concentration of micelles (CMC), electrical conductivity, pH, and optical density of solutions is established. The critical association of concentration is determined for lignosulfonate: C LS 0.13–0.14 mol/dm 3 . An increase in the surface activity of lignosulfonate is noted upon raising the temperature of and adding nitric acid to an LS–H 2 O system. The established effects (a drop in σ l–g ) are explained by an increase in the coefficient of diffusion of LS macromolecules and a change in the intensity of the associative-dissociative processes of counterions and the LS polyanion. The positive effect nitric acid has on the surface activity of SDS is noted and found to reduce surface tension at the liquid–gas interface and CMCs. Associative processes in SDS–HNO 3 systems are also confirmed by measuring the optical density of the considered systems.