Redox potential and proton demand in an anaerobic palladium (II) reducing culture of Desulfovibrio desulfuricans seroval

Abstract

Microbial recovery of Pd is emerging as a clean alternative bioremediation processes as compared to the traditional physical and chemical recovery processes, and Sulphate-reducing bacteria have drawn a great deal of attention because they have proven to have excellent metal reaction properties for Pd. However, to effectively reduce Pd (II) to its elemental Form a clear understanding of its particle physics is needed as well as the limitations posed by its occurrence in chelated states on the adsorption and uptake by living organisms. Thus, the pH of the solution has a significant role in the interaction and uptake Pd (II) ions leading to its reduction. Therefore, the aim of the study was to investigate the use of sulphate-reducing bacteria isolated from sludge from a wastewater treatment plant, and a pure isolate of Desulfovibrio desulfuricans DSM642 in the reduction of 2mM of Pd (II) from pH 1 – 10 at the expanse of formate as an electron donor, using HCl and NaOH to adjust the pH. After 12 h of incubation the results revealed a maximum of 90 % and 83 % of palladium reduction at pH 4 by sulphate-reducing bacteria and Desulfovibrio desulfuricans respectively and a low reduction percentage was observed at pH values lower than 3. This was attributed to chloride ion interference at low pH values. Nevertheless sulphate-reducing bacteria proved to be the better choice as a potential organism to bioremediate Pd contaminated environments.