Influence of typical soil minerals on ureolytic bacteria-induced carbonate precipitation

Microbial-induced carbonate precipitation (MICP) has been widely applied in soil remediation, stabilization and soil carbon storage. This study investigated the effects of different soil minerals on carbonate production during MICP. Aqueous sorption experiments, along with chemical and microstructural analyses, were conducted to monitor the progress and performance of MICP. Montmorillonite significantly enhanced carbonate production, while quartz, kaolinite and goethite adsorbed free Ca2+ from the solution, slowing the formation of calcium carbonate without affecting the overall carbonate yield. Calcite and vaterite were identified as the primary carbonate phases, with vaterite dominating (accounting for similar to 90% of the crystalline calcium carbonate). However, montmorillonite substantially increased the proportion of calcite (from 9% to 52%). The enhancement may be attributed to the lower Ca2+ adsorption capacity of montmorillonite, which helps maintain sufficient Ca2+ in solution and promote direct calcite precipitation. Additionally, interactions between montmorillonite and ureolytic bacteria may also protect bacteria from being co-precipitated with carbonate minerals. Soil minerals were also found to accelerate the urease activity of ureolytic bacteria, with goethite having the strongest effect. Since carbonate was not a limiting factor in the experiment, goethite had no significant impacts on carbonate yield. This study sheds light on the potential application of MICP under different soil mineral conditions.