RESUMO
One silicate bacteria strain SDB6 with good performance in silicon removal was isolated and screened from soil. Based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence analysis, SDB6 was identified as Bacillus mucilaginosus strain. The effects of nitrogen source, pH, temperature, rotate speed and medium volume on the growth of SDB6 were investigated. The above factors were optimized using the orthogonal design. The optimized condition was described as follows: 10 g/L yeast, 250 mL flask with 50 mL culture medium, pH 7.5, 30 degrees C, 180 r/min. The bioleaching of un-desilicated and desilicated fly ash using the adapted Aspergillus niger AS 3.879M strain was carried out for 20d. The results indicated that the metal extraction yield in bioleaching increased obviously with desilication treatment comparing to that without desilication treatment. The extraction yield of Cu, Mn, Cr, Zn and Fe from desilicated fly ash was 31%, 75%, 60%, 60% and 48%, respectively. The total metals extraction yield of desilicated fly ash increased to 50%. The TCLP results of the fly ash after bioleaching indicated that the leaching toxicities of the treated fly ash were far lower than the regulated levels of China and permitted to the further landfill or reuse.