A Comprehensive Study of CO2 Capture Using Attapulgite and Novel Hybrid Attapulgite/13X Zeolite Composite: Kinetic, Isotherm, and Thermodynamic Analysis

Abstract

In this study, a novel attapulgite/13X zeolite composite was synthesized in varying ratios (1:1, 2:1, 1:2) and evaluated for enhanced CO2 capture performance. The composite was prepared via a simple hydrothermal method and characterized through XRD, FTIR, BET, SEM-EDX, and TGA analyses. Results confirmed improved structural stability, increased surface area, and greater porosity relative to pristine attapulgite. The composite with a 1:2 ATP/Z13X(13X zeolite) ratio demonstrated the highest CO2 adsorption capacity (2.2 mmol g-1) at 25 degrees C, nearly tenfold higher than that of pure attapulgite (0.21 mmol g-1), owing to improved textural characteristics and synergistic effects between components. Adsorption was favored at lower temperatures and higher adsorbent dosages, while elevated CO2 partial pressures enhanced uptake capacity. Kinetic analyses indicated that physisorption governed the process, best described by the pseudo-first order and Elovich models. The adsorption mechanism conformed well to the Freundlich and Dubinin isotherms, consistent with multilayer sorption on heterogeneous surfaces. Thermodynamic evaluations revealed that the process is spontaneous and exothermic, with Delta G degrees ranging from-11.15 to-11.69 kJ mol-1 and Delta H degrees of-9.70 kJ mol-1, confirming the physical nature of adsorption. The composite also exhibited excellent cyclic stability over 11 regeneration cycles with only a 2.8 % capacity loss. These findings demonstrate the composite's promise as a cost-effective and durable adsorbent for post-combustion CO2 capture applications.