CO2 adsorption on biochar from co-torrefaction of sewage sludge and leucaena wood using microwave heating

Abstract

Abstract Microwave co-torrefaction of sewage sludge and leucaena wood was carried out to produce biochar for the adsorption of CO2. Three mixing ratios of sewage sludge and leucaena wood were 75:25, 50:50, and 25:75. The individual and blended biomass sample were torrefied at a microwave power level of 250 W. Mass and energy yields decreased whereas carbon and fixed carbon contents increased with increasing mixing ratio of leucaena wood. The biochar with higher carbon content could be capable of adsorbing more CO2 molecules. The adsorption capacity of pure leucaena wood biochar was approximately 53 mg/g, almost four times as that of pure sewage sludge biochar. The more fraction of leucaena wood in the blend would possess an adverse effect on the composition or property of biochar, resulting in lower CO2 adsorption capacity. Four kinetic models were applied to analyze the reaction kinetics of CO2 adsorption on biochar. The CO2 adsorption on biochar was best fitted by the pseudo-second-order kinetic model. The relatively low correspondence with the intraparticle diffusion kinetic model may imply that the CO2 adsorption on biochar is more governed by adsorption reaction.