CdS-loaded Fe-doped graphitic phase carbon nitride with type-II heterojunction as visible-light driven photo-Fenton catalyst for efficient degradation of Ofloxacin in water

The key to building an efficient photo-Fenton system lies in designing and preparing materials with dual photocatalytic and Fenton reaction activities to achieve effective synergy between the two processes, thereby significantly improving the degradation efficiency of organic pollutants. In this work, the CdS-loaded Fe-doped graphitic carbon nitride (CdS/Fe-g-C 3 N 4 ) with a type-II heterojunction was prepared in situ using a hydrothermal approach and employed as an efficient photo-Fenton catalyst for degrading antibiotics. Under optimized conditions (pH 2.0, catalyst concentration of 1.0   g/L and 800   μL of 0.1   mol/L H 2 O 2 ), the system achieves a degradation rate of 95.49% for 100   mg/L OFL within 80   min, with a rate constant (k) of 0.0447   min -1 . This is 22.35 times and 3.49 times higher than those of the CdS/Fe-g-C 3 N 4 +H 2 O 2 system and the light+CdS/Fe-g-C 3 N 4 system, respectively. The photocatalyst retained relatively high photocatalytic activity after 7 cycles, and it is appropriate for degrading many kinds of quinolone antibiotics. Mechanistic studies indicate that the type-II heterojunction formed between CdS and Fe-g-C 3 N 4 drives the directional migration of photogenerated electrons from the conduction band of CdS to that of Fe-g-C 3 N 4 , facilitating the reduction of Fe 3+ to Fe 2+ and significantly accelerating the generation of active radicals (∙OH). Analysis via mass spectrometry (MS) and the T.E.S.T. toxicity assessment software indicates that OFL undergoes stepwise transformation into a series of low-toxicity or non-toxic intermediates during degradation. This research provides a feasible and effective way to treat wastewater with high-concentrations of antibiotics in the industrial field.