Effects of different Mg/Ca molar ratio on the formation of carbonate minerals in microbially induced carbonate precipitation (MICP) process

Abstract

Traditional MICP technology has been extensively applied to improve soil properties and solidify heavy metal contaminated soil. However, the traditional product performance of calcite is far less than that of huntite, dolomite, and other carbonate minerals. Therefore, the soil strength and environmental safety after curing cannot reach the safety index. This study has examined the distribution of carbonate minerals induced by microorganisms under different Mg/Ca ratio. Compared with the sample with 0 Mg/Ca content, the unconfined compressive strength (UCS) can be increased by 1–5 times by increasing the content. By X-ray diffraction (XRD) and thermogravimetric analysis (TGA), the contents of different carbonate minerals under different Mg/Ca content were determined semi-quantitatively. The microscopic results have also shown that the introduction of microorganisms can provide nucleation sites for the synthesis of dolomite and huntite. MICP experiment coupled with Quantum ESPRESSO calculations revealed the mechanism of microbial influence on the formation of carbonate minerals under different Mg/Ca conditions through first principles calculations and nucleation kinetics. These findings advance our understanding of the reaction mechanisms and pathways of biogenic precipitation of carbonate minerals, and provide insights into the artificial quantitative synthesis of dolomite.