Carbon capture induced changes in Deccan basalt: a mass‐balance approach

Previous studies on the Deccan basalt–water–CO2 interaction were focused on numerical simulations and experimental validation that revealed carbonate formation, but restricted to low temperatures and for a shorter period. However, during prolonged interactions, silicates restricted carbonates from forming, and thus necessitated for comparative mass‐balance calculations of parent basalt, neo‐formed mineral and dissolution products to understand apposite parameters that control the reaction extent and optimal geochemical conditions. To examine these interactions, mass‐balance calculations have been attempted. A gradual increase in HCO3− concentration and basalt dissolution is concomitant with the increase in experimental run time; thus, the pH of the solution is affected. X‐ray diffraction and scanning electron microscope–energy dispersive X‐ray spectrometer analyses revealed the presence of carbonates in the post‐experiment residue (run for a shorter period). Owing to gradual carbonate decrease in the residue, Ca2+, Fe2+ and Mg2+ released from basalt gradually increased in the leachate at 100°C. But with the progression of time at 200°C, more secondary silicates were formed and incorporated Mg2+ and Si4+, which led to a decrease in Mg2+ and Si4+ concentrations in the leachate. Mass‐balance calculations revealed that the maximum amount of CO2 is mineralized (22.88 mol%) from the ions derived from the parent basalt at 100°C under 5 bar CO2 and 70 h of experiment running time. But, for longer periods of experiments, the rate of ionic interactions as well as CO2 mineralization is almost ceased. Thus, the rate of dissolution is affected by temperature, but the amount of CO2 mineralization is directly a function of the basalt–water–CO2 interaction time. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.