Novel microorganisms for the treatment of Ni and V as spent catalysts

Oil refining industry has used a great amount of catalysts, which once exhausted due to metal and hydrocarbon poisoning are disposed in special confining sites. Catalyst disposal represents a serious environmental problem due to the potential risk of metal leaching by natural events. The necessity to treat great amounts of catalysts and the existence of microorganisms that coexist with metals suggest that microorganisms can be used for the treatment of hazardous wastes such as spent catalysts. The aim of the present study was to isolate microorganisms from rich metal sites, mines, soils and water from rivers close to mines and then evaluate their ability to remove Ni and V from spent catalyst. Twenty-six isolates were obtained from samples using 9K liquid media and from them, only twelve isolates presented a minimum inhibitory concentration (MIC) higher than 200 ppm of Ni and V, then were evaluated for their ability to remove Ni and V in 9K liquid media added with 16% (w/v) pulp density of the catalyst. Results showed that isolates MNSH1-9K^-1 and PRGSd-9K-4 had the highest removal for Ni and V corresponding to 149.5 mg Kg^-1 and 920.5 mg Kg^-1, respectively and were identified by sequencing of 16S ribosomal RNA gene as Bacillus megaterium and Bacillus subtilis, respectively.