Heavy metals recovery from electroplating sludge by the multi-steps of leaching, electrodepositing and precipitating

A combined process of acid-leaching, electrodepositing and ammonium jarosite precipitating was developed to recover heavy metals from electroplating sludge. About 95% of copper and nickel, 90% of chromium and 86% of iron were extracted from the sludge with 10% H₂SO₄ leaching. More than 99% of copper was recovered from the leaching solution with electrodepositing process. The left solution after copper recovery was then treated with ammonium jarosite precipitating process, about 99.9% of chromium and iron could be deposited as chromium ferrite in this process. Finally, the left solution was treated with electrodepositing process again for nickel recovery, and about 57% of nickel could be recovered in this process under the condition of initial pH 5.5, cell voltage 5.5V and amount of boric acid 12g.