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

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.