Novel Combination of Bioleaching and Persulfate for the Removal of Heavy Metals from Metallurgical Industry Sludge

Abstract The objective of this study was to remove heavy metals from the metallurgical industry sludge by bioleaching alone and bioleaching combined with persulfate (PDS). The results showed that the removal of Cu, Zn, Pb and Mn reached to 70%, 83.8%, 25.2% and 76.9% by bioleaching alone after 18 d, respectively. The experiment of bioleaching combined with PDS was carried out in which the optimal additive dosage of K2S2O8, 8 g/L, was added to bioleaching after 6 d. After 1 h, the removal of 4 heavy metals reached 75.1, 84.3, 36.7 and 81.6%, respectively. Compared with bioleaching alone, although the increase in removal efficiency was not obvious, the treatment cycle was distinctly shortened from 18 d to 6 d + 1 h. Scanning electron microscopy (SEM) results showed that the surface morphology of the sludge was changed significantly by the combined treatment. The content of heavy metals was significantly reduced after bioleaching combined with PDS by energy dispersive X-ray spectroscopy (EDX). The treated sludge mainly existed in a stable form, and the bioavailability was reduced with European Community Bureau of Reference (BCR) morphology analysis. Therefore, this study proved that the combination of bioleaching and PDS was an efficient method to remove heavy metals from metallurgical industry sludge.