Model for the physical activation of biochar to activated carbon

Biochar is a carbon-rich material that is a co-product of the thermochemical conversion of biomass to liquid or gaseous products. A possible high-value application of biochar is the production of activated carbon. Biochar from biomass can be physically activated with a mild oxidant such as steam or carbon dioxide. A new model is proposed to describe the physical activation of pyrolytic biochar to activated carbon. The primary model assumption is that activation deepens but does not widen the pores. Measurements confirmed that the average pore diameter remained at about 1.9 nm. The new model successfully predicts the yield and specific surface area of activated carbon produced from olive residues. The pyrolysis conditions significantly impact the quality of the activated carbon. For example, biochar produced at higher heating rates contains more pores that, when cleared by physical activation with carbon dioxide, provide an activated carbon with a higher specific surface area, reaching about 1300 m 2 /g. • New model for biochar physical activation to activated carbon. • Model assumes that physical activation deepens but does not widen the pores. • Model predicts yield and specific surface area of activated carbon. • Biochar production conditions affect the activated carbon specific area.