Optimizing CHA-type zeolite synthesis via dry gel conversion method for direct air capture of CO2: Effects of seed addition, H2O/Gel ratios, crystallization conditions, and aging time

Carbon dioxide (CO₂) is the most prevalent greenhouse gas emitted by human activities, contributing significantly to global warming. Developing efficient and more environmentally friendly CO₂ capture technologies is crucial in addressing this environmental challenge. This study synthesized CHA-type zeolite using the environmental-friendly dry-gel conversion (DGC) method, with an emphasis on optimizing key synthesis parameters. The resulting CHA-type zeolite exhibited a surface area of 71 m²/g and a pore volume of 0.163 cm³/g. The CO₂ adsorption performance of CHA-type zeolite synthesized via DGC method was evaluated for the first time under direct air capture conditions (434 ppm CO₂) with 60 % relative humidity. Across ten adsorption cycles, the CHA-type zeolite synthesized from a gel composition of Si/Al = 75 demonstrated a CO₂ capture capacity in the range of 0.068 ± 0.011 mmol-CO₂/g-sorbent, which is relatively high compared to other zeolites under humid conditions. The cyclic adsorption tests indicate that the material maintains its performance over repeated capture cycles. These results highlight the potential of CHA-type zeolite, synthesized using the environmentally friendly DGC method, for efficiently capturing low concentrations of CO₂.