On the physical activation of biomass and urban waste chars for water treatment and CO2 adsorption

Abstract

Different industrial chars, a subproduct result of the valorization of agroforestry, urban, and industrial residues by pyrolysis, were valorized using them as carbon precursors of activated carbons. The char derived from olive stones, acacia, pine residues, artificial cellulose, and spent recovered fuel (SRF, mixed urban waste, paper, and plastics) was submitted to physical activation with CO2 (750 °C and 1 h). The activation led to materials with moderate surface area, i.e. 340–370 m2 g−1, except for the SRF (136 m2 g−1), and high micropores contribution (up to 83 % with olive stones). The chemical composition was characterized by elemental analysis, X-ray photoelectron spectroscopy, and temperature programmed desorption, which corroborated the presence of carbonyl and quinone groups. The activated samples were efficient in the adsorption of CO2 from post-combustion gases (maximum uptake, 121 mg g−1 at 273 K and 100 kPa), strongly dependent on the micropores’ contribution. The best sample displayed stable CO2 uptake in dynamic cycles of adsorption–desorption. The activated samples were also evaluated as potential candidates for the adsorption of lead and caffeine in water decontamination.