Effects of pH on MICP curing of cadmium-contaminated tailings
The microbial induced calcium carbonate precipitation(MICP)method is regarded as an environmentally sustainable approach for the solidification and remediation of contaminated soils.However,there are limited researches dedicated to understanding the impact of pH on the MICP treatment of heavy metals.In this study,the MICP remediation experiments involving cadmium(Cd)solution and Cd-contaminated tailings using Sporosarcina pasteurii ATCC 11859 at varying pH levels of 5,7,9,and 11 are conducted.The results indicate that in the aqueous solution tests,the effective immobilization of Cd2+occurs across the pH range of 5 to 11.The optimal immobilization of Cd2+is observed at a pH of 9.In contrast,during the consolidation and remediation tests on tailings,the introduction of acidic drenching solutions expedites the leaching of Cd2+from the tailings.In this context,the MICP primarily transforms the acid-soluble fraction of Cd within the tailings into reducible and residual states.Importantly,the effectiveness of this passivation process exhibits a positive correlation with the rate of carbonate generation.The analytical characterization through FTIR,XRD,XPS and SEM-EDS of biomineralization precipitation offers insights into the mechanisms underlying the fixation of heavy metals by the MICP and the solidification of tailings.The MICP accomplishes the immobilization of heavy metal ions through a combination of biosorption and calcium carbonate adsorption,ion exchange and co-precipitation processes.Furthermore,the MICP enhances the friction angle of soil particles and promotes cohesion among them through coating,bonding and bridging effects.
microbial-induced calcite precipitationpHsolidification and remediation of contaminated soilCdmicro-mechanism
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维普
