Application of Integrated Microbial Processes for Heavy Metal Recovery from Industrial Wastes of Buenos Aires, Argentina

Abstract

To allow the final disposal of galvanic sludge from a wastewater treatment plant of automotive factory, integrated microbial processes were performed to release and recover nickel and zinc contained in the solid residue. The metals were successfully leached using sulfuric acid continuously produced by Acidithiobacillus thiooxidans biofilm on elemental sulfur. The best condition using a sludge pulp density of 1 % w/v and a dilution rate of 0.22 h−1 100 % allowed more than 90 % of nickel and zinc dissolution, respectively; higher values of dilution rate and/or pulp density decreased the percentages of metal dissolution. The recovery of metals from the leachates was performed by continuous adsorption on Undaria pinnatifida biomass after raising the pH up to 4. Adsorption processes allowed great recoveries of nickel and zinc from monometallic solutions at the lowest flow rate (100 and 90 %); the recoveries from the leachates were not so good and to increase them three fixed bed columns in series were used reaching approximately 50 and 80 % of nickel and zinc recovery respectively, even at high dilution rates (more than 1.5 h−1). This integrated process could be applied on a higher scale.