The precipitation of calcium carbonate induced by Sporosarcina pasteurii (S. pasteurii) has garnered considerable attention as a novel rock and soil reinforcement technique. The content and structure of calcium carbonate produced through this reaction play a crucial role in determining the rocks’ and soil’s reinforcement effects in the later stages. Different potential gradients were introduced during the bacterial culture process to enhance the performance of the cementation and mineralization reactions of the bacterial solution to investigate the effects of electrification on the physical and chemical characteristics, such as the growth and reproduction of S. pasteurii. The results demonstrate that the concentration, activity, and number of viable bacteria of S. pasteurii were substantially enhanced under an electric field, particularly the weak electric field generated by 0.5 V/cm. The increased number of bacteria provides more nucleation sites for calcium carbonate deposition. Moreover, as the urease activity increased, the calcium carbonate content generated under an electric potential gradient of 0.5 V/cm surpassed that of other potential gradient groups. The growth rate increased by 9.78% compared to the calcium carbonate induced without electrification. Significantly, the suitable electric field enhances the crystal morphology of calcium carbonate and augments its quantity, thereby offering a novel approach for utilizing MICP in enhancing soil strength, controlling water pollution, and mitigating seepage. These findings elevate the applicability of microbial mineralization in engineering practices.

In order to improve the effect of microbial-induced calcium carbonate precipitation (MICP) in tailings reinforcement, sodium citrate, an organic matrix with good water solubility, was selected as the crystal form adjustment template for inducing calcium carbonate crystallization, and the reinforcements of tailings by MICP were conducted in several experiments. The effects of sodium citrate on the yield, crystal form, crystal appearance, and distribution of calcium carbonate were analyzed by MICP solution test; thus, the related results were obtained. These showed that the addition of a proper amount of organic matrix sodium citrate could result in an increment in the yield of calcium carbonate. The growth rate of calcium carbonate reached 22.6% under the optimum amount of sodium citrate, and the crystals of calcium carbonate were diverse and closely arranged. Based on this, the MICP reinforcement test of tailings was carried out under the action of the optimum amount of sodium citrate. The microscopic analysis using CT and other means showed that the calcium carbonate is distributed more uniformly in tailings, and the porosity of samples is significantly reduced by layered scanning analysis. The results of triaxial shear tests showed that adding organic matrix sodium citrate effectively increased the cohesion, internal friction angle, and peak stress of the reinforced tailings. It aims to provide a novel idea, a creative approach, and a method to enhance the reinforcement effect of tailings and green solidification technology in the mining environment.

The governance of uranium tailings aims to improve stability and reduce radionuclide uranium release. In order to achieve this goal, the uranium removal solution test and uranium tailings grouting test were successively carried out using microbially induced calcium carbonate precipitation (MICP) technology. The effect of MICP on the reinforcement of uranium tailings and the synchronous control of radionuclide uranium in the tailings were discussed. The solution test results show that Sporosarcina pasteurii could grow and reproduce rapidly in an acidic medium with an initial pH of 5. The uranium concentration decreased with the increase in MICP reaction time, and the removal efficiency reached 60.9% at 24 h. In the solidification test of tailings, the strength of tailings improved significantly after 12 days of reinforcement, with an increase in the cohesion of tailings by 2.937 times and an increased internal friction angle of 8.393°. The peak stress value of solidified tailings at the surrounding pressure of 50 kPa increased by 1.87 times, and the uranium concentration in the discharge fluid decreased by 76.91% compared to the blank group. This study provides valuable insights and references for safely disposing of uranium tailings.