College of Energy and Environment, Inner Mongolia University of Science and Technology, Baotou, 014010, China.
School of Civil Engineering, Yancheng Institute of Technology, Yancheng, 224051, China.
World J Microbiol Biotechnol. 2024 Jun 5;40(7):232. doi: 10.1007/s11274-024-04015-w.
Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu, Pb, Zn, and Cd were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES.
微生物诱导碳酸钙沉淀（MICP）已被用于固化含有放射性核素（如 Th 和 U）和重金属的稀土渣（RES），效果良好。然而，微生物胞外聚合物（EPS）在 MICP 固化 RES 中的作用尚不清楚。在这项研究中，提取了球形赖氨酸芽孢杆菌 K-1 的 EPS，用于吸附、诱导碳酸钙（CaCO）沉淀和固化 RES 的实验。通过评估放射性核素和重金属的浓度和形态分布以及固化体的抗压强度，分析了 EPS 在 MICP 固化 RES 和稳定放射性核素和重金属中的作用。结果表明，EPS 对 Th（IV）、U（VI）、Cu、Pb、Zn 和 Cd 的吸附效率分别为 44.83%、45.83%、53.7%、61.3%、42.1%和 77.85%。EPS 溶液的添加导致微生物表面形成纳米级球形颗粒，这些颗粒可以作为积累骨架，促进 CaCO 的形成。在固化过程中添加 20 毫升 EPS 溶液（处理组）后，固化体的最大无侧限抗压强度（UCS）达到 1.922 MPa，比 CK 组高 12.13%。与 CK 组相比，处理组固化体中可交换态 Th（IV）和 U（VI）的含量分别降低了 3.35%和 4.93%。因此，EPS 增强了 MICP 固化 RES 的效果，并降低了 RES 长期封存过程中放射性核素和重金属可能带来的潜在环境问题。
