Process and anodic reaction mechanism of cadmium electrically enhanced cementation on zinc plate under an ultrasonic field in ammoniacal system
(1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. Environmental Engineering Vocational College, Ganzhou 342000, China)
2. Environmental Engineering Vocational College, Ganzhou 342000, China)
Abstract: Cadmium was replaced by zinc in ammoniacal system using an electrically enhanced method under ultrasonic waves. Five main influencing factors were investigated by a single-factor experiment to determine the optimum parameters. Cyclic voltammetry and linear sweep voltammetry were applied to investigating the reaction mechanism of electrically enhanced cementation of cadmium on a zinc plate. The optimum parameters were a temperature of 35 °C, a cathode-to-anode area ratio of 1:2, an anode current density of 15 A/m2, an ultrasonic frequency of 40 kHz a reaction time of 6 h and an ultrasonic power of 100 W. The extraction rate was 99.21%, and the production of byproduct “floating sponge cadmium” was inhibited. The analysis of the cyclic voltammetry and linear sweep voltammetry diagrams showed that ultrasonic waves can promote and accelerate the replacement reaction, decrease the voltage requirement of the electrically enhanced replacement reaction, and change the reaction steps. In addition, increasing the temperature and ultrasonic power can promote and accelerate electrically enhanced replacement reactions and decrease the electric potential requirement.
Key words: cadmium; electrically enhanced cementation; ultrasonic; electrochemical mechanism; floating sponge cadmium