New insight into the adsorption of sulfadiazine on graphite-like biochars prepared at different pyrolytic temperatures

This study investigated the adsorption of sulfadiazine (SDZ) with four biochars prepared at 600, 700, 800 and 900 °C, and probed the potential rule connecting their chemical properties and adsorption capacities. Results showed that increasing the pyrolytic temperature, specific surface area, pore volume, aromaticity and aromatic cluster lateral size (La) of biochar markedly improved its adsorption capacity for SDZ. The maximum adsorption capacities (qm) of biochar600, biochar700, biochar800 and biochar900 for SDZ were 3.44, 17.87, 86.13 and 206.03 mg g−1, respectively. The pyrolytic temperature of 700 °C was the key temperature for the graphite-like biochar preparation, beyond which the La of biochar rapidly expanded. Compared with the pyrolytic temperature, specific surface area, pore volume and aromaticity of biochar, the La values of the four biochars exhibited a good positive linear correlation with their qm, indicating for the first time that La is an effective indicator to predict the adsorption capacity of graphite-like biochar. Density functional theory calculation further revealed that larger aromatic clusters could accommodate more SDZ molecules, and that the interaction among SDZ molecules in turn increased their binding energy with biochar. These findings in this study provide useful information for designing various efficient biochar adsorbents in the future.