Amine-functionalized disordered hierarchical porous silica derived from blast furnace slag with high adsorption capability and cyclic stability for CO2 adsorption

Abstract

This study proposes a novel solution to the challenge of achieving high cycle stability in CO2 adsorbents prepared through impregnation with organic amines. Specifically, industrial waste blast furnace slag was used to prepare a support material called BHF, which possesses three pore structures: micropores, mesopores, and macropores. This unique structure facilitates high loading of organic amines and improves CO2 adsorption effectiveness. To counteract agglomeration effects caused by loading large amounts of organic amines, the morphology and skeleton of the carrier material were analyzed in detail. The results showed that the rough “hive” morphology, disordered cell-like skeleton structure and abundant pores of BHF allows for uniform dispersion of polyethyleneimine (PEHA), an organic amine, and provides advantageous transportation of CO2 molecules within the adsorbent. Based on the study of kinetics, activation energy, and isosteric heat of adsorption, the adsorption mechanism of 70PEHA-BHF was determined to be a chemical-physical binding adsorption. The adsorption-diffusion mechanism suggests that the rate-limiting step is film diffusion. Furthermore, the 70PEHA-BHF adsorbent achieves a balance between CO2 adsorption capacity and cycle stability. At 80 °C and 15 vol.% CO2, the CO2 adsorption capacity of 70PEHA-BHF is 6.27 mmol/g, with only a 1.43 % CO2 loss after 10 cycles of testing. It anticipates that this newly developed 70PEHA-BHF adsorbent will provide additional possibilities for the application of hierarchical porous materials in CO2 adsorption research.