Bioleaching of heavy metal-contaminated sediments by indigenous Thiobacillus spp: metal solubilization and sulfur oxidation in the presence of surfactants

The efficiency of surfactant application to improve or inhibit metal solubi lization and sulfur oxidation kinetics during the bioleaching of heavy meta l-contaminated sediments was studied in suspension-leaching experiments. Th e river sediment used contained large amounts of fine particles and organic matter. Three types of surfactants were tested: sodium dodecylsulfate (SDS ), a C-12/14-alkanolethoxylate (Prawozell F1214/5N), and a wettable sulfur (Netzschwefel 80 WP). Adding 10 mmol SDS/1 led to transient inhibition of a cidification, metal solubilization and sulfur oxidation. Inhibiting bioleac hing for just 14 days required about ten times more SDS than the amount use d for mine waste mitigation. The use of Prawozell resulted in poor inhibiti on; and using of wettable sulfur did not improve leaching efficiency. The b ulk of these surfactants was sorbed onto the solid particles immediately on application, while the remainder in the aqueous phase disappeared within a few days.