Heavy metal pollution potential of zinc leach residues discarded in Cinkur Plant

Abstract

In this paper, results of the study on heavy metals solubility behaviour of filter cakes from leaching of clinkerized Waelz oxide and flue dust collected during clinkerization in Cinkur plant are given. The release of heavy metals into water was investigated by subjecting the cakes to solubility tests systematically. The effect of contact time, pH, liquid/solid ratio and successive extractions on the releasing of heavy metals (Cd, Pb, Mn and Zn) into water was examined and their concentrations in the solutions were compared to the various limits for surface waters. Also, 'Extraction procedure tests' approved by EPA were applied to the both residues to determine whether concentration of metals released from them are over toxicity limits given by EPA for solid wastes. Solubilization of metals from filter cakes was found to be a function of liquid/solid ratio, contact time and pH of mixture. Depending upon these parameters, the concentration of solubilized metals from the cakes is various. However, the pH of medium is most effective parameter for the solubility of filter cakes. The release of metals into solution was accelerated by increasing acidity, whereas solubilization of Pb was not affected very much. The concentration of Cd and Pb in the extracts obtained from filter cakes by applying EPA extraction procedures at pH 5 are over 1.0 and 5.0 mg/L which are toxicity limits, respectively. The concentration of other metals in the solution are above the limits given by various quality standard for surface water. From these findings, it can be resulted that leach residues are hazardous wastes for environment.