Enhanced CO2 adsorption in synthesized cube-shaped zeolitic 4A framework

This study addresses the urgent need for efficient and cost-effective CO₂ capture materials by exploring the synthesis of zeolite 4A using natural kaolin as a precursor. Through a controlled hydrothermal process, a highly crystalline Na-zeolite A framework was synthesized and rigorously characterized using XRD, SEM, FTIR, and BET analyses and its CO₂ performances were investigated under varying temperatures and pressures. The finding revealed that the produced NaA zeolite exhibited a CO₂ maximum uptake of 3.625 mmol/g at −20 °C and 13 bar. This result surpasses previously reported values for zeolite 4A, showcasing the material's enhanced adsorption capabilities. The equilibrium data were simulated using Freundlich, Langmuir and Sips isotherms. Based on the coefficient of determination (R²), the best result of the equilibrium data fit with the Sips isotherm at different adsorption temperatures. Thermodynamic studies showed spontaneous and exothermic adsorption behaviour with a ΔH of −18.385 kJ/mol, ΔS of −55 J/mol.K, and ΔG of −4.471 kJ/mol obtained at −20 °C. Thermodynamic and isothermal modeling confirmed the exothermic and spontaneous nature of the adsorption process, reinforcing the material's potential in sustainable CO₂ mitigation.