Enhanced bioremediation of hexavalent chromium via Stenotrophomonas acidaminiphila 4–1 assisted with agricultural wastes-derived biochar

Abstract

Chromium (Cr) contamination in soil poses high toxicity risks to organisms. In this study, a Cr(VI)-resistant strain was isolated from oil-contaminated soil and designated as Stenotrophomonas acidaminiphila 4–1. The optimal removal efficiency of Cr(VI) (67.4 %) was achieved by employing the response surface methodology, with a glucose concentration of 6.1 %, soil moisture content of 31 %, inoculation dose of 4.5 mL, and initial Cr(VI) concentration of 0.2 mg·g−1. The strain 4–1 was immobilized in biochar derived from the pyrolysis of agricultural waste, including corn straw, loofah, and reed straw. In the loofah biochar-4–1 group, the removal efficiency of Cr(VI) was 74.94 % when the initial concentration of Cr(VI) was 0.2 mg·g−1. The biochar-immobilized strain 4–1 exhibited superior removal efficiency and tolerance towards Cr(VI) compared to the single free strain 4–1.The FT-IR results revealed that the surface functional groups of reed straw biochar exhibited a higher abundance compared to those of corn straw biochar and loofah biochar. The predominant form of Cr(VI) in untreated soil was found to be residual form, while the proportion of Fe-Mn oxides form increased from 7.9 % to 18.8 % within a span of 14 days. Notably, loofah biochar-4–1 exhibited the ability to convert unstable chromium species into stable forms within the soil. This work offers a specific instructive method to for remediating Cr polluted sites.