You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Book
Title:
Glycine-Mediated Leaching-Mineralization Cycle for Co2 Sequestration and Vaterite Production from Coal Fly Ash
:
Dual Functions of Glycine as a Proton Donor and Receptor
Description:
CO2 mineralization using solid alkaline waste is one of the promising technologies to mitigate global warming. However, the state-art-technologies involved Ca/Mg leaching and ensued mineralization still struggle with the slow reaction kinetics and frequent pH swings assisted by exogenous chemicals consumption (i.e., low pH for Ca/Mg leaching but high pH for CO2 dissolution and solid carbonates precipitation). This study proposed a glycine-mediated leaching-mineralization cycle (LMC) process, which can simultaneously achieve high Ca/Mg leaching, high mineral carbonation efficiency, and production of high-purity vaterite from coal fly ash (CFA) at mild operating conditions in an in-situ recyclable amino acid solution. The technical feasibility of the process was initially investigated in individual leaching and mineral carbonation experiments in glycinate (Gly) solutions using a typical CFA. A greater improvement of Ca2+ leaching capacity (12896 mg/L) and CaCO3 yield (186 g/kg) in the Gly solution was achieved than that in water, which was only 961 mg/L and 4.25 g/kg, respectively. Mineralogy and morphology analysis revealed that pure vaterites were obtained after the carbonation reaction. The mechanism exploration revealed that Gly-species acted as a proton donor and chelating agent in the leaching step which enhanced the Ca/Mg leaching, a proton receptor in mineralization step which accelerated CO2 mass transfer, and a crystal regulator in carbonates precipitation. In addition, the cyclic performance of the LMC process was investigated in multicycle leaching-carbonation experiments. Results showed that the leaching capacities, CaCO3 yield, and Gly loss were similar in five cycles of LMC experiments, verifying that the process is stable