Impact of pyrolysis heating methods on biochars with enhanced CO2/N2 separation and their incorporation in 3D-printed composites
Inês de Sousa Correia, Marina Ilkaeva, Micaela Castellino, Sergio Bocchini, Rui M. Novais, Luís Mafra, Nuno P.F. Gonçalves, Mirtha A. O. Lourenço
Abstract
N-doped biochars, derived from chitosan sourced from waste crustaceous shells, were produced via microwave-assisted pyrolysis at temperatures ranging from 400 to 800 °C to enhance CO 2 and N 2 separation. Their performance was compared with biochars from conventional pyrolysis. Microwave-derived biochars exhibited superior CO 2 adsorption capacity at 25 °C and 100 kPa (0.78 – 1.56 mmol g −1 ) compared to conventionally produced ones (0.55 – 1.43 mmol g −1 ). Increasing the pyrolysis temperature up to 600 °C significantly improved biochar properties, including surface area, pore volume, and CO 2 adsorption capacity. Microwave-derived biochar featured enhanced surface area, larger pore volumes, and unique morphologies, requiring, on average, 61 % less preparation time. The higher ultramicroporosity and N-species concentration correlated with superior performance in the biochar produced at 600 °C. In gas mixture experiments (20 % CO 2 and 80 % N 2 ) under flow conditions, these biochars showed rapid adsorption/desorption rates due to enhanced macroporosity at samples produced at 600 and 800 °C, facilitating gas diffusion along the ultramicropores. Adsorption heat analysis indicated that the CO 2 adsorption is predominantly driven by physisorption, supported by complete sample regeneration when applying N 2 flux or increasing the temperature during desorption. The study also explores the feasibility of 3D-printing a composite using the most effective biochar and inorganic polymers sourced from waste, presenting potential benefits for industrial applications. • Microwave pyrolysis enhances biochar CO 2 adsorption capacity, selectivity, and kinetics. • Graphitic valley-N/ pyridinic-N-oxide species, along with macro- and ultramicroporosity, enhance CO 2 uptake. • 3D-printed composites comprised 20 wt% biochar and waste-derived inorganic polymers. • 3D-printed composite shows a four-fold higher CO 2 adsorption than the biochar-free composite.