Enhanced microbial remediation of uranium tailings through red soil utilization.

Seepage of uranium tailings has become a focus of attention in the uranium mining and metallurgy industry, and in-situ microbial remediation is considered an effective way to treat uranium pollution. However, this method has the drawbacks of easy biomass loss and unstable remediation effect. To overcome these issues, spare red soil around the uranium mine was used to enhance the efficiency and stability of bioremediation. Furthermore, the bioremediation mechanism was revealed by employing XRD, FTIR, XPS, and 16S rRNA. The results showed that red soil, as a barrier material, had the adsorption potential of 8.21-148.00 mg U/kg soil, but the adsorption is accompanied by the release of certain acidic and oxidative substances. During the dynamic microbial remediation, red soil was used as a cover material to neutralize acidity, provide a higher reduction potential (<-200 mV), and increase the retention rate of microbial agent (19.06 mL/d) compared to the remediation group without red soil. In the presence of red soil, the anaerobic system could maintain the uranium concentration in the solution below 0.3 mg/L for more than 70 days. Moreover, the generation of new clay minerals driven by microorganisms was more conducive to the stability of uranium tailings. Through alcohol and amino acid metabolism of microorganisms, a reducing environment with reduced valence states of multiple elements (such as S, Fe, and U) was formed. At the same time, the relative abundance of functional microbial communities in uranium tailings improved in presence of red soil and Desulfovirobo, Desulfocapsa, Desulfosporosinus, and other active microbial communities reconstructed the anaerobic environment. The study provides a new two-in-one solution for treatment of uranium tailings and resource utilization of red soil through in-situ microbial remediation.