Sorption of metal ions from aqueous solutions by thermally activated electroplating sludge

The sludge waste obtained from metal plating industries has been converted into a low-cost sorbent material. The thermally treated activated electroplating sludge is characterized, as well as its use for the removal of metal ions. The effect of contact time, the pH, the sorbate concentrations, the mixture of metal ions and the temperature on the sorption of lead, copper, zinc and nickel were studied in batch experiments. Kinetic studies were undertaken in order to make clear the mechanism of the process. The sorption on electroplating sludge follows both Langmuir and Freundlich's models. The degree of removal of metal ions was found to be dependent on the final pH of the contact solutions. The percentage of the sorbed metal ions rapidly rises at pH above 4.2-5.5. Some experiments were also carried out for chemical regeneration of the exhausted electroplating sludge. The order of preference of sorption of meal ions in a single and in a multicomponent system has been established.