Magnesium-based basic mixtures derived from earth-abundant natural minerals for CO2 capture in simulated flue gas

Abstract

Magnesium-based adsorbents with high theoretical CO2 uptakes, moderate regeneration energy, and good cyclic working stability show promise for intermediate-temperature CO2 capture from flue gas stream. Identification of low-cost materials for fabricating highly efficient magnesium-based adsorbents is one significant challenge for their large-scale applications. In this work, magnesium-based basic mixtures derived from earth-abundant natural minerals were employed as CO2 adsorbents. CO2 sorption performance of the adsorbents was evaluated using a fixed-bed reactor. Several kinetic equations were adopted to describe their CO2 sorption kinetic behaviors. Results show that the BM-HM and BM-BR adsorbents calcined from hydromagnesite and brucite possess attractive CO2 uptakes (1.73 and 1.67 mmol CO2/g) at 200 °C. The Avrami fractional kinetic model is expected to accurately predict the equilibrium CO2 uptakes, and the adsorbents show relatively fast CO2 sorption rate. The desired adsorbents exhibit favorable working stability with low loss-in-capacity of 5.65% and 5.33% over 10 repeated cycles. Characterization analyses indicates that the adsorbents own great physicochemical parameters, which will facilitate the diffusion and adsorption of gaseous reactants. Moreover, the dispersion of the basic mixtures in flake and sheet-like geometry can benefit the adsorbents reduced internal diffusion resistance and enhanced MgO utilization efficiency. These are associated with their excellent CO2 sorption performance. The scheme provides significant environmental implications as it will provide an attractive route towards cost-effective CO2 abatement and waste management.