Mechanism Of Efficient Remediation Of U(Vi) Using Biogenic Cmc-Fes Complex Produced By Sulfate-Reducing Bacteria

Uranium in groundwater during uranium mining activities urgently needs to be remediated through effective and environmental-friendly approaches. The reduction and immobilization of soluble U(VI) using biogenic carboxymethyl cellulose modified iron sulfide complex (biogenic CMC-FeS complex) is one of the emerging and innovative methods. However, its removal mechanism is largely unknown. Here, biogenic CMC-FeS complex with extracellular polymeric substances (EPS) and CMC was successfully synthesized by sulfate-reducing bacteria (SRB) and showed highly dispersible capacity. The tryptophan and tyrosine, which were the main components in EPS produced by SRB on CMC-FeS surface, significantly increased the U(VI) removal capacity of the biogenic CMC-FeS complex compared with chemically synthesized CMC-FeS. U(VI) removal was attributed to the adsorption of soluble U(VI) by = FeO+, CMC, tryptophan, and tyrosine on the biogenic CMC-FeS complex, following its reduction by S2-, S-2(2-) and Fe2+. Moreover, biogenic CMC-FeS complex with CMC-to-FeS molar ratio of 0.0005 performed well in the presence of bicarbonate (5 mM), humic acid (10 mg/L), or co-existing cations such as Pb2+, Ni2+, Cd2+, Mn2+, and Cu2+ (200 ug/L) at pH 7.0, and displayed relatively high oxidation resistance and stability ability. This work provides an in-depth understanding of the biogenic CMC-FeS complex for the U(VI) removal and contributes to the development of cost-effective U(VI) remediation technologies.