Morphology and distribution of cemented product formed via cementation over Zn in zinc sulfate solution relevant to roast-leach-electrowin process

Abstract

The morphology and composition of cemented products formed by Cu cementation in a ZnSO4 solution containing Cu2+ using Zn as the cementation agent were investigated. The influence of several factors on the characteristics of the cemented products, such as the temperature and pH of solution, ultrasound field, and suspended SiO2 particles, was studied separately. The cemented products were characterized using optical microscopy, scanning electron microscopy with energy dispersive X-ray, and X-ray diffraction. The Cu2+ content in the solution after the cementation process was determined using inductively coupled plasma-atomic emission spectroscopy. The results show that the cemented products can be effectively removed from the Zn surface when the rotating Zn sample is immersed in the solution containing suspended SiO2 particles, enhancing the Cu cementation and increasing the utilization efficiency of Zn especially for its addition near the stoichiometric amount. The high-power ultrasound can form a cemented product layer with large cracks favoring a solution permeation through the product layer; additionally the formation of basic Zn salts is enhanced, which are detrimental to Cu cementation. The pH of the solution greatly impacts on the morphology and composition of the cemented product on the Zn surface in the pH range of 0.5–4.5; a low pH of 0.5 or 1 can expose a large fraction of the Zn surface without the cemented product coverage. The enhanced Cu cementation at a higher temperature was confirmed by more cemented product obtained after 4-h cementation at 60 °C than those at lower temperatures.