Regeneration and reuse of iron hydroxide adsorbents in treatment of metal-bearing wastes

Sludge from a treatment process using iron was exposed to a mildly acidic solution to investigate iron hydroxide's capacity to collect metals from waste. Batches of iron hydroxide were regenerated and reused 50 times to treat both synthetic and real plating waste. Treatment efficiency was very high and steady, and there was no indication of deterioration in any aspect of process performance. Over time, the treated metals were concentrated in the regenerant solution and may be recoverable. The acid and base requirements were comparable to those for conventional coagulation. Overall, the process appears promising for metal treatment, sludge minimization, and possibly metal recovery. J. Water Pollut. Control Fed.. 61, 481 (1989).