Study on the pH Dependence for Copper Activation of Sphalerite

Abstract

The pH dependence of copper activation on sphalerite was studied by measuring the adsorption of copper ions as a function of pH. The adsorption of copper ions was maximum at about pH 5～6 and decreased rapidly in both the acid and akaine region. From the results obtained, it was recognized that the pH dependence for the adsorption of copper ions on sphalerite was remarkable. The cause for the decrease of the copper adsorption on sphalerite in the alkaline region was investigated. The dependence of concentration of copper ions in the solution for the copper adsorption on sphalerite was examined. From the results, it was recognized that the copper adsorption on sphalerite decreased with a lowering of the concentration of copper ions in the solution. Then, the kinetics for the adsorption of copper ions on sphalerite was investigated. The reaction rate of the copper adsorption on sphalerite was shown by the reaction equation of the 1st order, and the relationship between the adsorption rate of copper ions on sphalerite and the agitation rate was characterized by a straight line in the log-log plot. The above results suggested that the decrease of the copper adsorption on sphalerite in the alkaline region might be due to the decrease of the copper concentration in the solution with the increase of the pH value, and consequently to the decrease of the diffusion rate at which the copper ions diffused to the surface of sphalerite from the bulk in the solution. The cause for the decrease of the copper ions in the acid region was analysed experimentally. With regard to the results, it was surmised that the formation of copper sulphide led to the decrease of the copper concentration in the solution. The formation of copper sulphide was caused by the generation of H₂S resulting in the dissolution of sphalerite in the acid solution. Accordingly, there was a decrease of the copper concentration in the solution and of the diffusion rate of copper ions. As mentioned above, the reaction rate of the copper adsorption on sphalerite was determined by the diffusion rate of copper ions.