Bioremediation of low-concentration uranium wastewater by Desulfovibrio multispirans H1MTZ23 mediated mineralization

Uranium (U) mining and nuclear operations introduce U into the environment, posing a dual threat of radioactive and heavy metal pollution. Given its economic feasibility and high selectivity, bioremediation technology plays a crucial role in this endeavor. Herein, a sulfate-reducing bacteria (SRB) Desulfovibrio multispirans H1MTZ23 was isolated from U mine soil. This study investigated the removal efficiency and underlying mechanisms of low-concentration U by this microorganism, with a particular focus on its mediated biomineralization process. Results indicated that the optimal pH for uranium adsorption by H1MTZ23 was 6, with a maximum equilibrium adsorption capacity of 212.8 mg/g. The adsorption kinetics of H1MTZ23 followed the pseudo-second-order model. Under varying hydrochemical conditions in growth systems (U: 0.25-5.0 mg/L; SO₄^2-: 338-6000 mg/L), the U removal efficiency ranged from 77.33% to 100%. The removal of U by strain H1MTZ23 resulted from the synergy of three processes: biosorption, bioreduction, and biomineralization. A potential biomineralization process of U by H1MTZ23 has been proposed, involving the following stages: surface adsorption, amorphous precipitation, crystallization, and crystal growth. This process begins with the formation of amorphous uranium precipitates, which subsequently transform into crystalline phases and gradually grow, ultimately resulting in the formation of large, needle-like, and schistose U minerals. These minerals are distributed both on the cell surface and within the periplasmic space. In summary, H1MTZ23 exhibits strong removal efficiencies for U and SO₄^2-, indicating significant potential for bioremediation of weakly acidic, U-containing wastewater with high sulfate content.