Oxidative pyrolysis for enhanced-CO2 adsorption capacity in biosolid-derived biochar

The study conducts the adsorption kinetic analysis of biosolid-derived biochar produced from pyrolysis and oxidative pyrolysis. The adsorption kinetic analysis is performed at three different temperatures. The characteristics of the adsorption and diffusion mechanisms are evaluated by applying adsorption kinetic models and diffusion mechanism models. The pseudo-first-order model (PFO) and the pseudo-second-order model (PSO) reveal that the CO 2 adsorption process of the biosolid can be categorised as physisorption with activation energy below 40 kJ/mol. The CO 2 adsorption capacities of the biochar produced at 700 °C, 800 °C, and 900 °C are 6.3, 7.9, and 6.4 mg/g at 45 °C, respectively. In contrast, the biochar produced from oxidative pyrolysis shows a CO 2 adsorption capacity of 7.5 mg/g at 45 °C. Film and intraparticle diffusions are primary rate-limiting factors of the adsorption process. The biochar samples maintain 84–85 % of their adsorption capacities after five cyclic tests. The present study demonstrates the CO 2 adsorption capacity of biosolid-derived biochar produced from different conditions of pyrolysis, providing an energy-efficient and sustainable solution to CO 2 adsorption with solid adsorbents. • The oxidative pyrolysis improved the CO 2 capacity of the biochar by 20 % at 45 °C. • The oxygenated functional groups on the biochar facilitated CO 2 adsorption. • The biochar maintained 84 % of CO 2 adsorption capacity after the reusability test. • The CO 2 adsorption of the biosolid-derived biochar was categorised as physisorption. • The low air concentration reduced the average pore size of biosolid-derived biochar.