Air pre-oxidation induced high yield N-doped porous biochar for improving toluene adsorption

In this study, high yield Nitrogen (N)-doped porous biochar for enhanced toluene adsorption was developed via a novel air pre-oxidation (APO) treatment. Stillage and ammonium phosphate were used as the carbon precursor and in situ nitrogen additive, respectively. A range of APO conditions, including temperature (150-400 degrees C), air flow rate (0-240 mL/min) and time (0.5-3.0 h) were explored for biochar production. The optimized biochar exhibited high yield (55.5%), N content (6.51 at%), surface area (762.9 m(2)/g) and pore volume (0.444 cm(3)/g), which significantly exceeded biochar produced without APO. The toluene adsorption capacity of APO treated biochar reached 437.8 mg/g, which was significantly higher than that produced without APO (296.4 mg/g). APO treatment improved the structural characteristics and surface chemistry of biochar, thereby improving its adsorption properties. Possible mechanisms were also discussed for both the APO induced biochar preparation process and toluene adsorption by APO treated biochar.