Effect of Sulphur Concentration on Bioleaching of Cr(III) and Other Metals from Tannery Sludge by Indigenous Sulphur-Oxidizing Bacteria

Abstract

An investigation on the effect of elemental sulphur concentration on bioleaching of Cr(III) and other metals from tannery sludge by sludge indigenous sulphur-oxidizing bacteria was performed. Elemental sulphur concentrations ranging from 5 to 40 g/L were tested during this study. The sludge solids concentration was fixed at 40 g/L. The results showed that the sludge pH decrease was faster and sharper with increased sulphur concentration. The time required to achieve the final pH (the lowest pH) was about 15 days irrespective of sulphur concentration. The leaching efficiencies of Cr(III), Al, and Fe, and