Thorough conversion of CO2 through two-step accelerated mineral carbonation in the MgCl2-CaCl2-H2O system

This study describes a two-step accelerated mineral carbonation technology at moderate temperatures and atmospheric pressure by choosing the “problematic ions for seawater utilization” as mineralizers in the simplified seawater-MgCl2-CaCl2-H2O system, that is, Ca2+ as the first mineralizer and Mg2+ in the residual solution as the second. Not only can carbonate ions generated from the absorption and ionization of CO2 be fixed by Ca2+ through the first carbonation process with the added alkali source, MgO, but HCO3− in the residual solution can also be mineralized by Mg2+ through the second carbonation process. Meanwhile, pure CaCO3 and MgCO3·3H2O, which have the possible benefit of reuse, can be obtained as by-products. Then, more variables were set to optimize the technical conditions to enhance the decalcification rate and carbon sequestration ratio, reduce the reaction time during the first mineralization and attempt to realize the combination of HCO3− and Mg2+ by adding NaOH to produce MgCO3·3H2O as another by-product in a moderate environment during the second mineralization.