Graphitic carbon nitride/biochar composite synthesized by a facile ball-milling method for the adsorption and photocatalytic degradation of enrofloxacin.

In order to enhance the removal performance of graphitic carbon nitride (g-C3N4) on organic pollutant, a simultaneous process of adsorption and photocatalysis was achieved via the compounding of biochar and g-C3N4. In this study, g-C3N4 was obtained by a condensation reaction of melamine at 550°C. Then the g-C3N4/biochar composites were synthesized by ball milling biochar and g-C3N4 together, which was considered as a simple, economical, and green strategy. The characterization of resulting g-C3N4/biochar suggested that biochar and g-C3N4 achieved effective linkage. The adsorption and photocatalytic performance of the composites were evaluated with enrofloxacin (EFA) as a model pollutant. The result showed that all the g-C3N4/biochar composites displayed higher adsorption and photocatalytic performance to EFA than that of pure g-C3N4. The 50% g-C3N4/biochar performed best and removed 45.2% and 81.1% of EFA (10 mg/L) under darkness and light with a dosage of 1 mg/mL, while g-C3N4 were 19.0% and 27.3%, respectively. Besides, 50% g-C3N4/biochar showed the highest total organic carbon (TOC) removal efficiency (65.9%). Radical trapping experiments suggested that superoxide radical (•O2-) and hole (h+) were the main active species in the photocatalytic process. After 4 cycles, the composite still exhibited activity for catalytic removal of EFA.