Separation and concentration of metals present in industrial effluent and sludge samples by using electrodialysis, coulometry, and photocatalysis

Samples of effluent and sludge collected from the metal plating industry were treated by electrodialysis (ED), coulometry, and photocatalysis. The effects of different ED parameters (such as flow rate, applied voltage and current) and the single pass and recirculation methods on the percentage reduction of ionic components of an effluent sample and the percentage concentration of metal ions in the sludge solution have been determined. A maximum of 40-60% reduction in the composition of effluent sample and about 39-47% concentration of metal ions in sludge solution have been obtained. The recirculation method for the concentration of metal ions at a high flow rate of sludge solution seems to be better than the single pass method at low flow rates. Copper, which is a valuable component in sludge samples, has been recovered by constant potential electrolysis with a coulombic efficiency of 90-97% and has also been deposited to 57-76% on a colloidal suspension of TiO2 particles using UV and natural sunlight. The effects of treatment of TiO2 with H-2 at 400 degrees C and the nature of a sacrificial electron donor in contact to TiO2 on the photodeposition of copper are discussed.