No abstract

Members of the genus Clostridia can reduce Pd(II) ions to form metallic Pd nanoparticles (bio-Pd). Cultures of C. pasteurianum BC1 were used to generate bio-Pd, which is primarily formed on the microbial cell wall. Batch experiments using C. pasteurianum BC1 cells loaded with bio-Pd showed efficient reduction of the organic azo dyes, methyl orange and Evans blue, while little reduction of dyes was observed in control experiments using Pd-containing heat-killed microbial cultures or Pd-free viable bacterial cultures. Degradation of azo dyes was found to occur via reductive hydrogenation of the azo-linkage. Molecular hydrogen, which is concomitantly generated by C. pasteurianum, is used in the reduction reaction. The process described in this study is a potentially viable alternative to current groundwater and wastewater treatment technologies that fail to adequately degrade the large quantities of hazardous spent textile dyes that are discharged into the environment each year.

Clostridia can synthesize catalytic nanoparticles in-situ at the zone of treatment. In essence, the microbial surface becomes the support for the catalyst, thus maintaining their high surface area. Concomitantly, microbes generate electron donors that cause reduction of contaminants. Current groundwater treatment technologies rely on delivering pre-formed catalytic nanoparticles into groundwater treatment zones and the addition of expensive molecular hydrogen to above ground pump and treat systems; two shortcomings that are overcome in this one-step process.