Synthesis of La and Ce modified X zeolite from rice husk ash for carbon dioxide capture

The porous material adsorbent X zeolite was prepared by using agricultural waste rice hull ash (RHA) and modified by ion-exchange into the rare earth metal zeolite of La and Ce. A series of characterization results, including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, N2 adsorption–desorption and pore size analysis, illustrated the effects of ion exchange modification on crystal, pore structure and morphology. The CO2 adsorption experiment was operated, and the adsorption amount of NaX and LaLiX was 6.14 and 4.36 mmol/g at atmospheric pressure, respectively. Three isotherm models were used to fit the pressure swing adsorption data. The Toth and DSL models were more accurate due to their ability to express heterogeneity. The isosteric heat and selectivity were obtained by the corresponding models and calculations. The results explained the mechanism of heat and gas uptake during adsorption and desorption. The CO2/N2 selectivity of LaNaX has enhanced more than three times. All modified zeolite samples maintained above 96.5% of initial adsorption after 20 adsorption–desorption cycles. The adsorption heat releases properties and long-term stability of the modified zeolite are superior. It demonstrates that such adsorbents can be used for long-term capture and separation of CO2 from the industrial exhaust gas.