Increased CO2 capture capacity via amino-bifunctionalized halloysite nanotubes adsorbents

The development of highly efficient and low cost CO 2 adsorbent becomes increasingly significant in order to achieve the goal of carbon neutrality. Herein we prepared a new type of 3-aminopropyltriethoxysilane (AP) and polyethyleneimine (PEI) amino-bifunctionalized adsorbent by grafting AP onto the acid thermally activated Halloysite nanotubes (HNTS) through the use of Si-OH. The results showed that the adsorption capacity of the CO 2 adsorbent (5-700-HNTS-20AP-40PEI) was 1.03 mmol/g at 50 °C and further increased to 1.51 mmol/g at 80 °C. The hydrogen bonding and dipole interactions between the amino groups in PEI and the hydroxyl and amino groups in AP promote the dispersion of PEI into pore channels of the carrier, thus reducing the aggregation and blockage. Moreover, the amino-bifunctionalized adsorbent exhibited satisfactory cyclic regenerability over 20 cycles. The analysis of adsorption kinetics and internal diffusion indicates that untreated HNTS is predominantly dominated by physisorption , whereas amino-modified solid adsorbents exhibit both physisorption and chemisorption with adsorption mainly occurring on the carrier surface.