Effect of zinc ion on copper speciation and adsorption on activated carbon

Abstract

This paper describes the effect of zinc ions on copper speciation and adsorption on activated carbon in solutions with varied cyanide levels and containing calcium. Batch and column adsorption experiments were carried out under atmospheric conditions at different levels of CN/Cu using two types of activated carbon. Raman analysis shows that CN/Cu molar ratio, ionic strength (by adding calcium ions to the solution), and zinc ions can be used to control copper speciation in cyanide solutions. The addition of Zn2+ to cyanide solutions causes the conversion of CN− and Cu(CN)43− species to Cu(CN)32−, and the concomitant formation of Zn(CN)42−, regardless of cyanide concentration and ionic strength. As Cu(CN)32− has a high affinity for the solid surface, copper adsorption was favored. The co-addition of Ca2+ to the solutions produces an even larger enhancement of copper adsorption on activated carbon and has no effect on zinc adsorption. Column experiments show a significant reduction in the volume of cyanide solution to be further treated and an important increase in the concentration of copper. These findings may aid in the design of copper and cyanide recovery strategies.