Exploring adsorption behaviors of NO, NH3, SO2, CO2, C7H8 from flue gases on X-zeolite derived from coal fly ash: Experimental and micro-calculation

Abstract

Coal-fired power plants generate substantial quantities of hazardous fly ash and gas pollutants, presenting significant environmental challenges. This study introduces an innovative approach to simultaneously address both waste streams by converting coal fly ash (CFA) into high-performance X zeolite adsorbents. The synthesized X zeolite showed exceptional surface area and well-defined crystalline structure, as confirmed by comprehensive characterization using SEM, XRD, FT-IR, BET, Raman, and TPD analyses. The adsorption performance of the synthesized X zeolite was systematically evaluated using low-concentration (1000 ppm) flue gas components including NH₃, NO, SO₂, CO₂, and C₇H₈ across operating temperatures of 20–100 ℃. Maximum adsorption capacities at 20 ℃ reached 1.58, 0.38, 1.16, 0.71, and 0.65 mmol/g for NH₃, NO, SO₂, CO₂, and C₇H₈ respectively, with NH₃ and SO₂ showing notably higher affinities. The selective adsorption behavior stems from strong interactions between polar gas molecules and the zeolite framework under combined dispersion and electrostatic forces. In-situ DRIFTs analysis coupled with DFT calculations revealed that bridging oxygen atoms (T-O-T) within the zeolite structure serve as primary adsorption sites, facilitating electron transfer with gas molecules. These findings demonstrate the potential of CFA-derived X zeolite for efficient multi-pollutant removal from flue gases while simultaneously addressing solid waste management in coal-fired power plants.