title: Effect of different types of elemental sulfur on bioleaching of heavy metals from contaminated sediments.
abstract: The application of two different types of elemental sulfur (S0) was studied to evaluate the efficiency on bioleaching of heavy metals from contaminated sediments. Bioleaching tests were performed in suspension and in the solid-bed with a heavy metal contaminated sediment using commercial sulfur powder (technical sulfur) or a microbially produced sulfur waste (biological sulfur) as substrate for the indigenous sulfur-oxidizing bacteria and thus as acid source. Generally, using biological sulfur during suspension leaching yielded in considerably better results than technical sulfur. The equilibrium in acidification, sulfur oxidation and metal solubilization was reached already after 10-14 d of leaching depending upon the amount of sulfur added. The metal removal after 28 d of leaching was higher when biological sulfur was used. The biological sulfur added was oxidized with high rate, and no residual S0 was detectable in the sediment samples after leaching. The observed effects are attributable to the hydrophilic properties of the biologically produced sulfur particles resulting in an increased bioavailability for the Acidithiobacilli. In column experiments only poor effects on the kinetics of the leaching parameters were observed replacing technical sulfur by biological sulfur, and the overall metal removal was almost the same for both types of S0. Therefore, under the conditions of solid-bed leaching the rate of sulfur oxidation and metal solubilization is more strongly affected by transport phenomena than by microbial conversion processes attributed to different physicochemical properties of the sulfur sources. The results indicate that the application of biological sulfur provides a suitable means for improving the efficiency of suspension leaching treatments by shortening the leaching time. Solid-bed leaching treatments may benefit from the reuse of biological sulfur by reducing the costs for material and operating.
authors.affiliation: UFZ Centre for Environmental Research Leipzig-Halle, Department of Bioremediation, Permoserstrasse 15, 04318 Leipzig, Germany. heinz.seidel@ufz.de
authors.forename: Heinz
authors.initials: H
authors.lastname: Seidel
authors.forename: Rainer
authors.initials: R
authors.lastname: Wennrich
authors.forename: Petra
authors.initials: P
authors.lastname: Hoffmann
authors.forename: Christian
authors.initials: C
authors.lastname: Löser
mesh_terms: D001673:Biodegradation, Environmental; D004785:Environmental Pollutants / Q000032:analysis*; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D019216:Metals, Heavy / Q000032:analysis*; D013455:Sulfur / Q000737:chemistry*; D016999:Sulfur-Reducing Bacteria / Q000254:growth & development*
chemical_list: D004785:Environmental Pollutants; D019216:Metals, Heavy; D013455:Sulfur