Interfacial kinetics regulation and electrochemical optimization in ultrasonic-induced sponge cadmium nucleation

The cementation method has become the dominant method for recovering cadmium from copper-cadmium slag leach solution due to its low cost and safety features. However, the conventional method has several limitations, including low zinc powder utilization, low sponge cadmium purity, and an extended production cycle. These limitations primarily stem from zinc powder agglomeration and the subsequent coverage of zinc particles by the product layer. In this study, the ultrasonic-enhanced zinc powder cementation process is proposed. Ultrasonic effectively dissociates the agglomeration and accelerate the reaction rate, improving the utilization of zinc powder and the grade of sponge cadmium. The cadmium cementation efficiency and the grade of sponge cadmium are increased by 24.56 % and 23.11 %. Kinetic experiments reveal that ultrasonic reduced the apparent activation energy by 21.34 kJ/mol. Moreover, the reduction potential exhibits a positive shift from -2.731 V to -2.432 V (vs. SCE). The current density increases from 0.146 A/cm² to 0.199 A/cm². The self-corrosion potential reduces from -1.411 V to -1.453 V (vs. SCE). Simple economic analysis indicates that the benefits under ultrasonic method are significantly higher than conventional method. This work provides new insights into the application of ultrasonic in the recovery of cadmium from copper-cadmium slag.