High-Gravity Intensified Electrodeposition for Efficient Removal of Cd ²⁺ and Recovery of Cd from Heavy Metal Wastewater

Abstract

Simultaneously and efficiently treating heavy metal wastewater and recovering heavy metals are the goal that industries pursuit. A novel Multi-concentric Cylindrical Electrodes-Rotating Bed (MCCE-RB) which could provide high-gravity fields was proposed to enhance electrodeposition for efficient treatment of Cd-containing wastewater and recovery of Cd in this paper. Under the optimal operating conditions covering current density of 53.1 A m^-2, wastewater circulation flowrate of 64 L h^-1, high-gravity factor of 15, NaCl concentration of 0.2 mol L^-1, initial pH value of 2, and initial Cd²⁺ concentration of 800 mg L^-1, the removal efficiency of Cd²⁺ reached 99.4% after 120 min electrodeposition. Compared with the results of electrodeposition in normal gravity field, the removal efficiency of Cd²⁺, current efficiency and the mass of deposits were increased by 18.4%, 15.7% and 35.4%, respectively. The cell voltage, electrodeposition time and total energy consumption (E_Total) were decreased by 21.7%, 42% and 21.2%, respectively. SEM, EDS, XRD and XPS analyses showed that the deposits were flaky and layered structure in high-gravity fields, avoiding the formation of dendrite in normal gravity field. The deposits were comprised of the mixture of Cd and Cd(OH)₂, and the percent weight of elemental Cd was 91.89% in the high-gravity field which was 19.17% higher than that in normal gravity field. The purity of Cd was improved in the high-gravity field. High-gravity intensified electrodeposition could serve as a clean, high efficient and low energy consumption method for treating heavy metal wastewater and recovering heavy metals simultaneously.

Keywords: High-gravity, Electrodeposition, Heavy metal wastewater, Cadmium, Recovery