Reutilization of biomass pyrolysis waste: Tailoring dual-doped biochar from refining residue of bio-oil through one-step self-assembly

The biochar with porous structure and functionalized surface from biomass waste is strongly appealing as a CO₂ adsorbent due to its cost-effectiveness and eco-friendliness. In this study, N/S dual-doped porous biochar was fabricated from bio-oil refining residue through one-step carbonization-activation combined with in-situ doping. The CO₂ adsorption performance and mechanisms of biochar were investigated in pure CO₂ and simulated fuel gas based on its porous architecture and physicochemical properties. Specifically, the biochar derived from refining residue had abundant pores with a high proportion of micropores (above 87%). In addition, the biochar prepared at 800 °C exhibited relatively outstanding CO₂ adsorption performance (2.21 mmol/g) due to its ideal pore structure and more abundant surface functional groups (N and S). Although the increase in induced temperature promoted the pore development of biochar to obtain a higher specific surface area (957.44 m²/g), it had no significant positive effect on the subsequent CO₂ adsorption. Moreover, biochar demonstrated excellent recyclability through ten consecutive adsorption-desorption. The pathway advocated here for tailoring porous biochar from bio-oil refining residue will open up a new perspective in exploring the large-scale preparation of biochar from waste by-products of biomass pyrolysis-refining system for CO₂ capture.