Glycine-induced synthesis of vaterite by direct aqueous mineral carbonation of desulfurization gypsum

Climate change is urgently calling for rapid methods to capture atmospheric carbon dioxide (CO 2 ). CO 2 can be sequestred into gypsum from gas desulfurization by carbonation to produce calcium carbonate (CaCO 3 ). However, CaCO 3 is produced as a mixture of polymorphs including calcite and vaterite polymorphs, which limits applications. Therefore, we present here a method to produce CaCO 3 enriched in the vaterite polymorph. We reacted CO 2 with gypsum from gas desulfurization in the presence of glycine. Carbonation products were analyzed by X-ray diffraction, scanning electron microscopy, electrospray ionization mass spectrometry, and Fourier transform infrared spectroscopy. Results show that vaterite content increases from 60 to 97% with increasing glycine concentration from 0 to 20 wt% and then kept a constant value, indicating that glycine promotes the formation of vaterite by inhibiting the growth of the calcite polymorph. We also observed that the intermediate glycinate calcium played a major role in stimulating vaterite growth. Overall, nearly pure vaterite was synthesized successfully by carbonation of gypsum in the presence of glycine.