Use of Reactive Species in Water for CO₂Mineralization

Various carbon capture and sequestration (CCS) technologies have been developed to address the issues concerning climate changes associated with anthropogenic CO2 emissions. In the present work, possibilities of mineralizing CO2 with the reactive species, such as Mg2+ ions, present in nature, such as seawater and produced water, have been explored. Laboratory tests conducted with solutions containing 1400 ppm of Mg2+ ions showed that nesquehonite [Mg(OH)(HCO3)·2H2O] is formed upon CO2 injection to the solution at an atmospheric pressure. The results showed that, for mineralization to occur, the pH should be raised above 6.8, as predicted from thermodynamics. Kinetic studies conducted at different temperatures showed that the nesquehonite formation involves an activation energy of 66.7 kJ/mol, which can be overcome by increasing the mass- and heat-transfer efficiency as well as the operative temperature. On the basis of the kinetics data obtained at a low agitation speed, the number and volume of the mineralization reactors required to capture CO2 emitted from a 600 MW coal power plant have been determined. In addition, the amount of alkalis needed to raise the pH for precipitation and, subsequently, to obtain the natural pH of seawater has been estimated.