[Isolation, identification of Acidithiobacillus sp. and its role in the removal of heavy metals from contaminated sediments].

A sulfur-oxidizing bacterium FD97 was isolated from heavy metal-contaminated river sediments. According to the morphological characteristics and sequence analysis of 16S rDNA of FD97, the strain was identified as Acidithiobacillus sp.. The effects of temperature on heavy metals bioleaching efficiencies from contaminated sediments by using Acidithiobacillus sp. FD97 were investigated in shake flask experiments. The tests were performed at four different temperatures in the range of 22-40 degrees C. The results showed that after 16 days of bioleaching, almost 70% of Zn, 90% of Cu, and 25% of Cr could be removed from the sediments, respectively. From the variations of pH reduction, sulfate production, and metals removal, the order of bioleaching efficiency at different temperatures was 34 degrees C > 28 degrees C approximately to 40 degrees C > 22 degrees C. The preferable temperature used for the future larger-scale bioleaching process is 28 degrees C. It was found that during the bioleaching process, temperature did not directly affect the metal removal process; the final level of metal removal achieved was highly correlated to sediment pH. When the pH decreased to 5.0, 3.5, and 2.5, the removal of Zn, Cu, and Cr began to increase sharply, respectively, and the maximum metal removal could be achieved when the pH decreased to below 2.0.