Advanced pseudopolymorph control of magnesium carbonates using structural properties of amines for CO2 utilization based on post-treatment of desalinated brine

Abstract Herein, we proposed a novel method for controlling magnesium carbonate pseudopolymorphs as part of the development of post-treatment technology for desalinated brine and CO2 from industrial plants. Mg(OH)2 was separated from reject brine using the pH swing method, and CO2 delivery into Mg(OH)2 was conducted by amine type CO2 carriers, including alkanolamine, alkylamine, and multi-amines with numerous amino groups, by utilizing the effects of their structural properties on pseudopolymorph control. The products formed by reaction between Mg(OH)2 and CO2-saturated amine carriers were analyzed by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy for verification of crystal properties and thermogravimetry for purity analysis. The results demonstrated that through use of appropriate amine type CO2 carriers, particular magnesium carbonates can be formed. In conclusion, we proposed a novel process for pseudopolymorph control of magnesium carbonates without the need for excessive changes in reaction conditions and additional transformation inhibitors. With further optimization for scale-up and the process design of a carbon capture and utilization (CCU) plant, the proposed method can contribute to the commercialization of CCU processes where particular types of magnesium carbonates are targeted. Further, post-treatment of desalinated brine, efficient mitigation and utilization of CO2 will be achieved simultaneously.