CO2 capture by kaolinite and its adsorption mechanism

•We investigate kaolinite for use as an adsorbent for CO2 capture.•Acid treatment of kaolinite improves its textural characteristics.•Its CO2 adsorption capacity also increases after the acid treatment.•Its CO2 adsorption is greater at room temperature and not at higher temperatures.•CO2 adsorption by kaolinite is mainly owing to physical adsorption.

The low-cost and naturally abundant clay mineral kaolinite was studied for use an adsorbent for CO2 capture. Samples of kaolinite were subjected to acid treatments to improve their textural properties, namely, its surface area and pore volume. It was found that the kaolinite sample treated with 3 M H2SO4 for 10 h reaction exhibited the highest Brunauer–Emmett–Teller (BET) surface area (18.9–74.3 m2/g) and pore volume (0.11–0.31 cm3/g). The CO2 adsorption capacity of kaolinite, which was ~ 0 mg-CO2/g-sorbent at 25 °C, increased to 3.4 mg-CO2/g-sorbent after the acid treatment. Moreover, it was found that the CO2 adsorption capacity of kaolinite was greater at room temperature than at higher temperatures. The CO2 adsorption by kaolinite, which was investigated using X-ray diffraction analysis, Fourier transform infrared spectroscopy, and CO2 adsorption isotherm measurements, was found to be mainly attributable to physical adsorption.