Green capturing of Ag from ultra-low concentration precious metal wastewater by electrodeposition assisted with electrocoagulation: Electrochemical behavior and floc characterization

As an environmental-friendly water treatment technique, direct electrodeposition (ED) encountered some difficulties to recover low-concentration metallic ions. This work proposed a novel electrodeposition assisted with electrocoagulation (ED-EC) process to remove and capture Ag+ from ultra-low concentration wastewater. Influences of operating parameters on the removal efficiency were investigated. Results showed that the Ag+ removal ratio of ED-EC increased to > 97.4 % compared to direct ED (<90 %), and Ag+ was reduced to < 0.1 ppm from an initial concentration of 2–20 ppm. Low current density, low pH and high Ag+ concentration improved electrodeposition, but weakened the formation and adsorption of the flocs by electrocoagulation. Aqueous Ag+ was captured and enriched in the flocs and the cathode deposit, where the Ag contents were > 3000 g/t and > 97 wt%, respectively. The economic assessment indicated that recovering Ag by ED-EC produced considerable benefits. Thus, this study provides meaningful guidance for resource recovery from precious metal wastewater.