Use of Acidithiobacillus for the recovery of heavy metals from industrial wastes

N. YAGNENTKOVSKY1, G. CABRERA REVUELTA2, M. VIERA 1, J. M. GÓMEZ MONTES DE OCA2, D. CANTERO MORENO2 AND E. DONATI1,A

Bariloche

Congreso; 18º Internatioanl Biohydrometallurgy Symposium; 2009

CINDEFI (CONICET LA PLATA, UNLP)

Abstract. Solid wastes from galvanic processes usually content high amount of heavy metals. Bioleaching can be an alternative for the treatment of such residues. Sulphur oxidizing bacteria of the genus Acidithiobacillus produce sulphuric acid from elemental sulphur, which can be used to solubilise heavy metals contained in solid phases. The aim of this work was to characterize two solid residues (called A and B) from different industries which applied galvanic processes and to remove the heavy metals present in them by bioleaching using Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans. Physical and chemical characterizations were conducted for both residues. These comprised: pH, humidity, metal content and metal speciation by sequential extraction. Bioleaching experiments were carried out in 100 ml cultures of the strains in 0K medium with 10 g / L of Sº adding different pulp densities of the residues. Periodically, pH, proton concentration, bacterial population and dissolved metal concentrations were evaluated. Sterile controls and inorganic leaching with sulphuric acid solutions were performed. Residue A was more alkaline than residue B (pH values 8.0 and 7.0 respectively). It was determined that the residue A contains Ni and Zn (14 and 59 mg / g residue approximately) mostly associated with easily leachable fractions, while residue B showed a high content in Cr(III) (115 mg / g residue) associated with less mobile phases. Results of the bioleaching tests showed that 60 and 80% approximately of the metals present in residue A can be removed for both strains when 0.5 and 1% of pulp density were used. At 2%, only A. thiooxidans was able to extract virtually 70% of the metals. For systems with higher pulp density, the solubilisation of both metals was negligible, probably because the alkaline conditions generated by the presence of greater amount of waste. In the case of residue B, 100% of metal can be removed for both strains when 0.5 and 1% of pulp density were used. Bioleaching of 2% of pulp density was partial (30% and 10% for At Af, respectively). As happened with residue A, the use of pulp densities higher to 2%, lead to a negligible solubilisation of chromium and a high pH.