Mineralogical and Thermochemical Characteristics of Dolomite Induced by Two Marine Microorganisms: Further Insights into Biomineralization

The mechanism of dolomite has been a major hotspot in geological research. However, most of the current studies mainly focus on single microorganisms and fail to fully consider the influence of marine microbial diversity on the precipitation of carbonate rock minerals. In this paper, two marine microorganisms (Bacillus sp. and Virgibacilus oceani), which can induce dolomite precipitation, were selected to induce dolomite precipitation in a culture solution that simulated the Mg²⁺/Ca²⁺ of modern oceans. Four systems were set up in this experiment, including the Bacillus sp. system, the Virgibacilus oceani system, the co-precipitation system (Bacillus sp. and Virgibacilus oceani), and the control system. The synergistic promotion of the dolomite was analyzed by comparing the changes in solution pH, ion consumption, morphology, mineralogical phase, and thermal stability in each experimental group. The experimental results show that the increase in pH value and the consumption of Mg²⁺ and Ca²⁺ in the coexistence of Bacillus sp. and Virgibacilus oceani are greater than those in the single microorganism system. The minerals induced by Bacillus sp. and Virgibacilus oceani were mostly small calcium carbonate particles and a small amount of proto-dolomite. However, the faster precipitation rates, larger particle diameters, higher proportion of proto-dolomite, and higher thermal stability of the calcium carbonate and proto-dolomite induced by the two microorganisms suggest that biomineralization facilitates the formation of stable dolomite and accelerates the precipitation of Mg²⁺ and Ca²⁺ for bioremediation purposes.