Removal of cadmium in leachate from waste alumina beads using electrochemical technology

US Air Force uses alumina beads (aluminum oxide) as a blast media in routine maintenance operations. These spent alumina beads fail to pass the TCLP test for their cadmium contents. A chemical process consisting of leaching and electrochemical methods is investigated for the feasibility of treating the alumina beads. Dilute nitric acid was found the most effective solution for cadmium leaching. Electrochemical reduction was able to reduce cadmium content in the leachate from 180 mg/L to 15 mg/L. With consumable aluminum electrodes, electrochemical coagulation reduced the cadmium concentration to less than 1 mg/L. Electroflotation was effective for metal sludge, ferric, aluminum, and ferrous hydroxide separations with the assistance of commercial surfactants.