Carbonation of heat-activated serpentine driven by Microcystis aeruginosa PCC7806

Abstract

The capture and storage of CO2 has been a critical strategy towards coping with global warming in recent years. Mineral carbonation is gaining much attention as a novel method of CO2 storage owing to its stability and safety. In this study, the mechanism and effect of carbonation of heat-activated serpentine [Mg3Si2O5(OH)4] driven by cyanobacteria were explored, taking Microcystis aeruginosa PCC7806 as an example. The serpentine was heated at different temperatures, and thermal decomposition of serpentine was characterized by simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The pH, ion concentrations, mineral composition and surface morphology in the process of interactions between the algae cells and heat-activated serpentine were analyzed. The results show that the serpentine can be transformed to forsterite after heat treatment at over 614 °C, and the medium for the addition of heat-activated serpentine at over 614 °C did not allow algae growth. The algae grew well in BG11 liquid medium with 400 °C heat-activated serpentine, and the pH of the culture liquid reached 10.2–10.3, which is in favor of the carbonation of serpentine. The analysis results show the carbonation of trace serpentine. Moreover, the carbonation effect of 400 °C heat-activated serpentine driven by the algae in a solid medium was the most significant, and the carbonate content of serpentine increased by 75.21% as detected by chemical analysis. XRD, SEM, and energy dispersive spectrometer (EDS) results indicate that amorphous CaMg(CO3)2 and MgCO3 were formed on the surface of serpentine driven by the algae. This study advances our understanding of the biological mechanism of serpentine carbonation, and provides a new way to fully exploit serpentine resources in carbon sequestration.