Room-Temperature CO2 Capture by a Zeolite-A Synthesized from Kaolin

CO₂ emissions have raised alerts worldwide due to their contribution to global warming. Thus, many efforts have been made to develop technologies to capture CO₂ from the atmosphere and interest in utilizing adsorbents originating from natural raw sources increasing sustainability. In this work, Zeolite-A was synthesized from Kaolin material. Kaolin was previously calcined at 650 °C to form the Metakaolin. The obtained Metakaolin was submitted to hydrothermal treatment in an aqueous solution of sodium hydroxide and treated at 60 °C for 24 h without using other sources of silica and alumina species. The materials were characterized by X-ray diffraction (XRD), ²⁷Al NMR, infrared spectroscopy (FTIR), N₂-physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The synthesized Zeolite-A material was evaluated in the CO₂ adsorption on a fixed bed reactor using a continuous flow system. The Yoon–Nelson model was used to predict the breakthrough behavior of CO₂ adsorption in a fixed bed reactor using Zeolite-A material as an adsorbent. The role of pretreatment temperature of Zeolite-A prior to the CO₂ adsorption capacity was accessed. Three different pre-treatment temperatures were used: 100 °C, 300 °C, and 400 °C. The Zeolite-A pretreated at 400 °C (Zeolite-A-400) exhibited the highest surface area. The CO₂ adsorption kinetics of the Zeolite-A materials indicated a pseudo-first-order (PFO) kinetics suggesting physical adsorption of CO₂ species on the Zeolite materials along with an intraparticle diffusion as the rate-controlling step of the whole adsorption process. The Yoon–Nelson rate constant (k_YN) values and the time (τ) required for 50% adsorbate breakthrough offered pieces of evidence for the rationalization of the superior adsorption capacity noticed for the Zeolite-A-400 sample.

Graphical Abstract