High-performance CO2 capture on amine-functionalized hierarchically porous silica nanoparticles prepared by a simple template-free method

Abstract

The adsorption of CO2 on polyethyleneimine (PEI)-functionalized hierarchically porous silica nanoparticles (PSNs), prepared by using rice husk as a silica source via a simple template-free method, was reported in this study. Compared with traditional alkaline fusion and surfactant-templating methods for preparing waste-derived porous silica materials as CO2 adsorbents, this method holds specific important advantages in being an inexpensive, and energy-saving process with faster production rate. The results revealed that the (NH4)(2)SiF6 salt formed during the synthetic process served as an effective porogen, which can be readily removed by washing with water. Additionally, the total pore volumes of PSNs materials were strongly correlated to the amount of (NH4)(2)SiF6. When evaluated as a support of PEI for CO2 adsorption, 55PEI/PSNs(12/14) could reach 159 mg/g at 75 degrees C under 15 % CO2, which was remarkably superior to those using waste silicate precursors reported in the previous literature. It was demonstrated that both PEI loading, and total pore volume of the PEI/silica composite sorbents, played key roles on CO2 adsorption. Besides, 55PEI/PSNs(12/14) also showed high stability during 20 cycles of adsorption-desorption operation, implying its high potential in post-combustion CO2 capture.