Effective reduction and removal of Cr(Ⅵ)and reductive dehalogenation of chlorophenol by hybrid bioinorganic catalytic processes

摘要

The ability of palladium coated cells of Desulfovibrio desulfuricans ATCC 29577 to reduce Cr(Ⅵ) to Cr(Ⅲ) was investigated. Complete reduction of 700 μM Cr(Ⅵ) took place in 24 hours at 30℃ using formate or hydrogen as the electron donor, but not lactate, whereas cells without bound Pd~0, or Pd~0 alone, did not reduce Cr(Ⅵ). Palladised biomass was also effective in the dehalogenation of 5 mM chlorophenol, suggesting a novel, multipurpose bioremediation strategy which may also be applicable in the treatment of recalcitrant polychlorinated biphenyls, since the latter are documented to be dehalogenated chemically via a palladised metal surface (Fe~0). Using Cr(Ⅵ) reduction as the test reaction at the expense of formate immobilised, palladised biomass reactors reduced 400 μM Cr(Ⅵ) from a 1 mM input solution (pH 7) with a flow residence time of approx. 5 h. No Cr(Ⅵ) reduction occurred using chemically-prepared or commercially-obtained Pd~0. Later tests using formate showed an optimum pH of 3. Waste solutions of platinum group metals (industrial processing wastes) were used as raw material for synthesis of the catalyst and used to reduce 1mM Cr(Ⅵ) quantitatively to soluble Cr(Ⅲ) continuously for several weeks.