Investigation of microwave-assisted regeneration of zeolite 13X for efficient direct air CO2 capture: a comparison with conventional heating method

This study investigates the regeneration of zeolite 13X for direct air CO₂ capture by comparing microwave-assisted and conventional heating methods in a fixed-bed reactor. Zeolite 13X, a high-surface-area solid adsorbent, was tested over three adsorption/desorption cycles under ambient conditions with approximately 400 ppm of CO₂. Microwave-assisted regeneration, optimized at 300 W for 10 min (350 °C), achieved a regeneration efficiency of 95.26%, with minimal loss in adsorption capacity (9%) across cycles. Conventional heating at 350 °C for 30 min achieved a comparable efficiency of 93.90% but required significantly more time and energy. The microwave technique operates via direct dielectric heating, selectively exciting polar species such as mobile Na⁺ ions within the zeolite framework. This localized and volumetric heating enhances CO₂ desorption without requiring reactor preheating or carrier gas flow, unlike conventional methods that rely on slower conduction and convection. As a result, microwave regeneration demonstrated a tenfold reduction in energy consumption (0.06 kWh vs. 0.62 kWh for conventional heating). Statistical analysis using ANOVA identified microwave power and regeneration time as key factors, with microwave power exerting the greatest influence. The study highlights the advantages of microwave-assisted regeneration, including reduced energy demand, shorter regeneration times, and enhanced scalability. These findings emphasize its potential as a transformative approach for advancing direct air capture technologies. Compared to conventional methods, microwave-assisted regeneration offers a more energy-efficient and practical solution for CO₂ removal from ambient air.