Abstract: The pollutants produced by in-situ leaching of uranium ore pose a hazard to groundwater resources through osmotic migration, which has significantly restricted the development of this leaching method. Microbial cementation can effectively reduce the permeability of sandstone uranium ore and prevent the pollutants migrating into the groundwater in the vicinity of the mining area. Therefore, in this study, sporosarcina pasteurii was chosen and tested for acid resistance. The permeability coefficients of the uranium ore sand cemented in condition of different concentrations of cementing solution, volume ratio of bacterial solution and cementing solution as well as grouting rounds were measured using a self-made experimental setup, then, the best value of these parameters was determined. In addition, the microstructure and mineral composition of uranium ore sand before and after bio-cementation were observed using scanning electron microscope (SEM) and X-ray diffraction spectroscopy (XRD) in order to explore the mechanism of the impermeability by bio-cementation. The results show that sporosarcina pasteurii still grows and reproduces well with high urease activity at pH value of 4, indicating that it can adapt to the acidic uranium ore sand. The formation of calcium carbonate can be promoted by increasing the concentration of cementing solution and the volume ratio of bacterial solution and cementing solution within a certain range, and the best cementing solution concentration and volume ratio are 1 mol/L and 1:3, respectively. The permeability reduction ratio of uranium ore sand reaches 95.33% after 7 rounds of bio-grouting. The permeability coefficient of uranium ore sand decreases with increasing the grouting round. The permeability coefficient of uranium ore sand is reduced by up to 99.75% after 11 rounds of bio-grouting, with a value of 2.8×10−5 cm/s. Calcite is the main crystal form of deposited calcium carbonate. It blocks the intergranular pore and cements the sand particles together, which is the main reason for the reduced permeability coefficient of uranium ore sand. The impermeability mechanism of uranium ore sand cemented by microbial induced calcium carbonate precipitation provides important theoretical guidance for the control and reduction of groundwater pollution.

Key words: sandstone uranium ore, in-situ leaching of uranium ore, microbial mineralization, permeability coefficient, impermeability