Synergistic electrochemical-cementation processes for selective cadmium recovery from Cd-Ni solutions

Abstract

Nickel and cadmium are critical materials in the clean energy sector, but their limited availability poses significant challenges. Recycling these metals from secondary sources can mitigate supply risks, yet their separation during recovery is often difficult, especially when striving to conserve energy and minimize environmental impact. This study proposed an electrochemical method for the efficient separation and recovery of cadmium from Cd-Ni solutions. Under optimal conditions of 0.5 V applied voltage, 10 g/L initial acid concentration, 50 °C temperature, and a 2h duration, over 95.6 % of cadmium was recovered with a purity of 93.3 %, while nickel loss was restricted to just 5.38 %. The high separation efficiency is attributed to the preferential reduction of cadmium over nickel, even at low concentrations, as confirmed by impedance spectroscopy and SEM analysis. Cadmium deposition occurred exclusively at the anode, with minimal nickel loss primarily resulting from the formation of Ni(OH)₂. Kinetic analyses revealed that zinc dissolution at both the anode and cathode followed a first-order rate, with the anode dissolving more rapidly, thereby facilitating cadmium deposition. This method offers a sustainable option for recovering these metals from secondary sources by effectively integrating electrochemical and cementation processes.