Hydrothermal interaction of sphalerite with copper sulfate solutions in the presence of sodium lignosulfonate

The present paper aims to study the efficiency of using sodium lignosulfonate surfactant for hydrothermal treatment of zinc sulfide with copper sulfate solutions. The solutions were analyzed by the optical emission spectral method; an ARL ADVANT’X wave X-ray fluorescence spectrometer was used to study cakes. MS Excel, OriginPro, and Statgraphics software packages were used for data processing. Particle size was determined using a Bettersize ST laser diffraction particle size analyzer. We have studied the effect of sodium lignosulfonate on the hydrothermal extraction of zinc from sphalerite. The addition of this surfactant enhances the precipitation of copper on the sphalerite surface, thus increasing the degree of zinc extraction into the solution. Effects of temperature (180–220°C) and concentration of lignosulfonate (0–1 g/dm 3 ), sulfuric acid (10–30 g/dm 3 ), and copper (6–24 g/dm 3 ) has been studied; optimal conditions for the maximum zinc extraction of 55–71% into the pregnant solution and copper cake precipitation of 45–83% were identified. Elevated temperatures increase the reaction rate and solubility of metals. Changes in the concentrations of sulfuric acid and copper affect the equilibrium of reactions and the efficiency of copper precipitation and zinc extraction into the solution. The performed experiments have resulted in the optimal parameters of hydrothermal treatment: 0.25 g/dm³ lignosulfonate concentration, 220°C temperature, 10 g/dm³ sulfuric acid concentration, and 15 g/dm³ initial copper concentration. For these parameters, 74% of zinc is extracted into the solution in 120 min and 83% of copper is deposited on the cake. Thus, the effect of sodium lignosulfonate on the hydrothermal treatment of sphalerite can be stated as positive: the concentration of this additive below 0.25 g/dm³ accelerates sphalerite treatment by 1.5–2 times.