Surfactants and their mixtures under conditions of autoclave sulfuric acid leaching of zinc concentrate: Surfactant selection and laboratory tests

Abstract

The influence of surfactants and their mixtures on the efficiency of the pressure leaching of zinc concentrates was studied by leaching tests and subsequent analysis, including granulometric and phase composition studies of the leaching products. Lignosulfonate (LS) and sodium dodecyl sulfate (SDS) were used as surfactants. Additional experiments were performed on artificial solutions to study the effect of surfactants on the solution surface activity by surface tension measurements. The obtained results indicated a synergistic effect of the combined LS and SDS addition, resulting in surface tension reduction. In a series of pressure leaching tests, the effects of the concentration of surfactants and their mixtures (CLS/SDS=0.2−0.8 g/L), temperature (T=120−140 °C), oxygen partial pressure (pO2=0.5−0.7 MPa), and time (t=20−120 min) on the extraction of zinc, iron, copper and indium into solution were investigated. Based on the results, optimal parameters were determined to carry out the leaching of zinc concentrates: surfactant mixtures of the composition CLS=0.6−0.8 g/L, CSDS=0.2−0.6 g/L, pO2=0.5 MPa, T=140 °C, and t=100−120 min. These optimal conditions result in extraction of 93%−94% zinc, 65%−66% indium, 64%−68% copper, and 48%−49% iron into solution.