Mechanism of ultrasound-assisted replacement for copper removal based on products morphology

In this paper, ultrasound-assisted copper removal from zinc sulfate solution was conducted, focusing on the mechanism of ultrasonic enhancement in copper removal by zinc replacement. The study used techniques including metallographic microscopy, scanning electron microscopy, X-ray diffractometry and Image J to characterize the morphology and distribution of the replacement product layer. The Cu(Ⅱ) concentration in the solutions at different purification stages was also analyzed by plasma emission spectrometry. The results showed that the ultrasonic intensity could affect the copper removal by replacement in purification. The low-intensity ultrasound (500 W) affects the interfacial products weakly, while the high-intensity ultrasound (2000 W) significantly affects the morphology and distribution of the solid product layer. Furthermore, it can reinforce the diffusion process in the solid product layer, and the generated thermal effect also contributes to the replacement reaction efficiency. The high-powered ultrasound leads to a discontinuous distribution of small sphere-like particles over the zinc surface, enlarging the contact area between the two phases. At the same time, it forms through holes in the solid product layer, reducing the structural resistance to diffusion of the solution.