A coupling model for simulating the synergistic remediation of uranium in groundwater by microorganisms and iron-based PRB.

Due to the complexity of uranium chemistry, the remediation of uranium contamination in groundwater remains challenging to assess. In this study, a biological permeable reactive barrier (Bio-PRB) consisting of sulfate-reducing bacteria (SRB) and biochar-Fe0@Fe3O4 was established. The removal process of U(VI) by the Bio-PRB was conducted through batch experiments and coupled numerical model. The results showed that SRB primarily removed U(VI) through reduction, which followed first-order reaction kinetics. Biochar-Fe0@Fe3O4 removed uranium via adsorption, with U(VI) forming uranyl carbonate complexes on the material surface. The remediation efficiency of both SRB and biochar-Fe0@Fe3O4 in simulated aquifer was significantly lower than that observed in static experiments due to the shorter hydraulic retention time. Microorganisms can effectively enhance biochar-Fe0@Fe3O4 performance. Compared with PRB, the Bio-PRB delayed the arrival of the uranium plume by 32 days, and the system lifespan was extended by 2.7 times. Increasing the thickness of the Bio-PRB is the most cost-effective way to improve remediation performance. Due to the nonlinear behavior of reaction kinetics and dose effects, only a slight increase in PRB width is required to address higher uranium concentration. The study can provide guidance for the design of groundwater uranium remediation systems in real sites.