Effect of temperature on removal of heavy metals from contaminated river sediments via bioleaching

The aim of this study was to determine the effect of temperature on the solubilization of heavy metals from contaminated river sediment by sulfur oxidizing bacteria taken from Ell-Ren River sediment. Of three temperatures tested (25degreesC, 37degreesC and 55degreesC), pH decrease was greatest at 37degreesC, indicating that, after acclimation, bacterial oxidizing activity is greatest at this temperature. At 55degreesC, pH change was similar to that which occurred with no inoculum added. The increase in sulfates and high pH at 55degreesC indicate that the indirect mechanism was not initiated at this temperature. Solubilization efficiency of total extractable Ni, Zn, Cu and Cr was high ( > 90%) at 37degreesC, whilst that of Pb was only 60.4%. Except for Pb, the optimal temperature for solubilization of total extractable heavy metal was 37degreesC. The order of average solubilization efficiency of total extractable heavy metals was Ni, Zn, Cu > Cr > Co, Pb. The solubilization efficiency of Pb and Co was markedly less than that of other heavy metals. Transfer of heavy metals between binding fractions was most apparent at 55degreesC before and after bioleaching. (C) 2003 Elsevier Science Ltd. All rights reserved.