Characteristics of Cr(VI) reduction by dissimilatory Fe(III)-reducing bacterium LQ25

Abstract:

[Background] Reducing Cr(VI) to Cr(III) by dissimilatory Fe(III)-reducing bacteria is an important way for remediation of chromium pollution. [Objective] This work examined the characteristics of Cr(VI) reduction by biogenic magnetite particles using dissimilatory Fe(III)-reducing bacterium Clostridium butyricum LQ25. [Methods] Strain LQ25 was grown under Fe(III)-reducing conditions and was used to produce biogenic magnetite particles using glucose as electron donors and insoluble iron hydroxide as the electron acceptor. The efficiencies of Cr(VI) reduction under Fe(III)-reducing conditions were examined with different Cr(VI) concentrations (5, 10, 15, 25 and 30 mg/L) added to the medium respectively. [Results] In the presence of iron hydroxide, strain LQ25 could grow within the set Cr(VI) concentration range with Cr(VI) reduction efficiency of 63.45%±5.13% at Cr(VI) concentration of 15 mg/L. When adding biogenic magnetite particles, Cr(VI) reduction efficiency of 87.73%±9.12% was obtained, increased by 38% compared with the control. Cr(VI) reduction by biogenic magnetite particles was decreased obviously with increasing pH solutions from 2.0 to 8.0. At pH 2.0, the reduction rate of Cr(VI) by biogenic magnetite particles was the highest, almost 100%. There were many pores on the surface of biogenic magnetite particles under scanning electron microscope. Biogenic magnetite particles showed XRD peaks include Fe(II) existed in the form of Fe(OH)₂.[Conclusion] These results indicated that dissimilatory Fe(III)-reducing bacteria and the biogenic magnetite particles could reduce Cr(VI), which will provide the evidence for the application of dissimilatory Fe(III)-reducing bacteria into the reduction of Cr(VI).

Key words:Fe(III)-reducing bacteria;Clostridium butyricum LQ25;biogenic magnetite;Fe(III) reduction;Cr(VI) reduction