Influence of pyrolysis atmosphere and temperature co-regulation on the sorption of tetracycline onto biochar: structure-performance relationship variation

[Display omitted] •Biochars are produced in air-limitation (AL), CO2, and N2 to adsorb tetracycline.•Biochars from AL and CO2 pyrolysis present better sorption performance.•The better sorption performance results from high SSA, pore volume, and ash content.•The sorption behavior of biochar from N2 pyrolysis depends on its graphitic degree.•The sorption ability of biochars from CO2 and AL pyrolysis is more pH-dependent. Presently, as the prevalent pyrolysis atmospheres, N2 is widely used, while air-limitation and CO2 are rarely considered, to produce biochar to adsorb tetracycline. This study thus used N2, CO2, and air-limitation to produce various biochars at 300 ∼ 750 °C, and explored their structure-performance relationship for tetracycline sorption. The maximum sorption capacities of biochars produced in CO2 and air-limitation were 55.36 mg/g and 71.11 mg/g (at 750 °C), respectively, being 2.34 and 3.01 times that of biochars produced in N2 (23.60 mg/g at 750 °C). Interestingly, except for high pore volume and specific surface area supported pore filling and sites providing effect, ash (containing metal cations, P-O, and S=O) induced complexing effect was the primary mechanism for tetracycline sorption, rather than hydrophobic effect, π-π interaction, and hydrogen bond caused by C composition. This study provides important information about adjusting the pyrolysis atmosphere to improve the sorption performance of biochar toward tetracycline.