Study on CO2 adsorption performance of biocarbon synthesized in situ from nitrogen-rich biomass pomelo peel

Abstract

Recycling biomass to prepare CO2 adsorbent has been emphasized due to the benefits such as easy availability of materials, green and sustainable. Furthermore, functional groups containing nitrogen can promote the capacity of biochar to adsorb CO2. Usually, the production of N-doped porous carbon involves the chemical addition of amines or compounds containing nitrogen, which leads to pore blockage. For this reason, pomelo peel was used as a nitrogen-rich precursor of biomass to achieve nitrogen self-doping in this paper, and ZnCl2 was uniformly loaded as an activator using the impregnation method. After carbonization at 800 ℃ and template removal, an efficient porous carbon adsorbent was obtained without adding extra nitrogen sources. The N content of the biocarbon was retained from 2.60 to 5.98 at% employing pre-carbonation. We also systematically analyzed the modification of the CO2 adsorption effect by ultra-microporous structure and N atom doping. The former content showed almost no linear correlation with the adsorption data, but rather a synergistic effect with N content influenced the adsorption results under environmental conditions. The optimal adsorption of CO2 was 3.01 mmol g−1 (25 °C, 1 bar) and 4.83 mmol g−1 (0 °C, 1 bar). In addition, the adsorbent PPC-4 has excellent CO2/N2 adsorption selectivity of 38 and cyclic adsorption performance.