Preparation and CO2 adsorption properties of TEPA-functionalized multi-level porous particles based on solid waste

In this paper, tetraethylenepentamine (TEPA)-functionalized solid waste-based porous particles were prepared by the wet impregnation method, and their functionalization characteristics and CO2 adsorption performances at different TEPA loadings were investigated. Through a scanning electron microscope test and a N2 adsorption/desorption test, it is found that, as the TEPA loading increases from 4 wt% to 20 wt%, the specific surface area and pore volume of the samples decrease slowly and micropores gradually disappear. Besides, the CO2 adsorption capacity of the samples was tested by a fixed-bed adsorption experimental device at 298 K and 0–1 bar. The results show that the CO2 adsorption capacity reaches the maximum (71.29 mg/g) at a 12 wt% TEPA loading, which is attributed to the high content of affinity sites in CO2. Furthermore, the effect of temperature (298–398 K) was investigated at 1 bar. It is concluded that an appropriate increase in adsorption temperature can enhance the flexibility of TEPA and greatly reduce its diffusion resistance. The highest adsorption capacity (83.05 mg/g) is achieved at 348 K. Then, the effect of pressure (0–40 bar) was analyzed at the optimal temperature (348 K) and optimal TEPA loading (12 wt%), and the results suggest that the adsorption capacity gradually strengthens with the increase in pressure, ultimately reaching a peak of 204.06 mg/g. The adsorption selectivities of CO2/N2 and CO2/H2 are 14.88 and 9.66, respectively, indicating that the porous particles have a stronger affinity for CO2 than for N2 and H2. The infrared spectra prove the formation of carbamates, which confirms that CO2 is sequestered in porous particles by chemical adsorption. The adsorption kinetics and adsorption thermodynamics results reveal the presence of both physical and chemical adsorptions of 12 wt% TEPA-porous particles in the adsorption process, and the chemical one is dominant.