微生物诱导的碳酸盐沉淀(MICP)已用于固化含有放射性核素(例如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治疗RES中的作用尚不清楚。在这项研究中,提取球形芽孢杆菌K-1的EPS进行吸附实验,诱导碳酸钙(CaCO3)沉淀和RES的固化。通过评估放射性核素和重金属的浓度和形态分布,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,和固化体的抗压强度。结果表明,EPS对Th(IV)的吸附效率,U(VI),Cu2+,Pb2+,Zn2+,Cd2+为44.83%,45.83%,53.7%,61.3%,42.1%,和77.85%,分别。EPS溶液的加入导致微生物表面形成纳米级球形颗粒,其可以作为促进CaCO3形成的累积骨架。在固化过程中加入20mLEPS溶液后(处理组),固化体的最大无侧限抗压强度(UCS)达到1.922MPa,比CK组高12.13%。处理组固化体中可交换性Th(IV)和U(VI)的含量分别降低了3.35%和4.93%,分别,与CK组相比。因此,EPS增强了MICP固化RES的效果,并减少了在长期封存RES期间可能由放射性核素和重金属引起的潜在环境问题。
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 (CaCO3) 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), Cu2+, Pb2+, Zn2+, and Cd2+ 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 CaCO3. 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.