Adsorption of CO₂ by alkali metals and weak alkali rare earth metals supported on aluminum pillared diatomite

Abstract

In this study, aluminum pillared diatomite loaded with alkali metals and weak alkali rare earth metals was prepared by impregnation method with cheap and abundant diatomite as raw material. Aluminum pillared diatomite loaded with alkali metals Cs, K, Na, Li and aluminum pillared diatomite loaded with weakly alkaline rare earth metals La, Nd, Tm were prepared respectively. Its physicochemical properties were studied by XRPD and N2 adsorption/desorption techniques, and characterized by thermogravimetric analysis, CO2 temperature programmed desorption and FTIR. The results show that the adsorption capacity of 5Cs/Al-PILC for CO2 is the highest, which is 2.355 mmol/g. The specific surface area and porosity of diatomite were improved by aluminum pillared modification, but the specific surface area and micropore content of metal loaded diatomite decreased slightly. The effect of alkalinity is greater than that of micropore amount. The adsorption performance of aluminum pillared diatomite adsorbent is affected by the synergistic effect of specific surface area, total micropore volume and alkalinity. Alkalinity is the main factor affecting the adsorption capacity. The adsorption process of CO2 on the sample is mainly chemical adsorption. The addition of appropriate amount of metal can enhance the alkalinity of the sample, and the adsorbed CO2 exists in the form of bicarbonate and carbonate. The adsorbent made from diatomite has low cost, can be used in industrial production, and has broad development prospects.