Formation of Soluble Organo-Chromium(III) Complexes after Chromate Reduction in the Presence of Cellular Organics

Journal Article · Fri Apr 01 00:00:00 EST 2005 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es048967g· OSTI ID:1154286

Puzon, Geoffrey J.; Roberts, Arthur G.; Kramer, David M.; Xun, Luying

Microbial reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] has been investigated as a method for bioremediation of Cr(VI) contaminated environments. The produced Cr(III) is thought to be insoluble Cr(OH)₃; however, recent reports suggested a more complex fate of Cr(III). A bacterial enzyme system, using NADH as the reductant, converts Cr(VI) to a soluble NAD⁺-Cr(III) complex, and cytochrome c-mediated Cr(VI) reduction produces cytochrome c-Cr(III) adducts. In this study, Cr(VI) reduction in the presence of cellular organic metabolites formed both soluble and insoluble organo-Cr(III) end-products. Several soluble end-products were characterized by absorbance spectroscopy and electron paramagnetic resonance spectrometry as organo-Cr(III) complexes, similar to the known ascorbate-Cr(III) complex. The complexes remained soluble and stable upon dialysis against distilled H₂O and over a broad pH range. The ready formation of stable organo-Cr(III) complexes suggests that organo-Cr(III) complexes are rather common, likely representing an integral part of the natural cycling of chromium. Finally, thus, organo-Cr(III) complexes may account for the mobile form of Cr(III) detected in the environment.

• Research Organization: DOE Office of Science Subsurface Biogeochemical Research (SBR) (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• OSTI ID: 1154286
• Journal Information: Environmental Science and Technology, Vol. 39, Issue 8; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English