Electron-rich oxygen enhanced Fe-doped g-C3N4 mediated Fenton-like process: Accelerate Fe(III) reduction and strengthen catalyst stability

Both the ≡Fe(III) reduction and the catalyst stability are the main obstacles limiting the application of such Fe-doped Fenton-like catalysts in endocrine disruptors removal. Herein, oxygen was introduced to the Fe-g-C3N4 to fabricate a newly Fe–O-doped catalyst FeCA-g-C3N4. The pseudo-first-order rate constant for bisphenol A (BPA) degradation in FeCA-g-C3N4 system is 2.6 times higher than that in the traditional Fe-doped g-C3N4 (FeCl3-g-C3N4) system. And the formation of Fe–O bond can strengthen the stability of the catalyst. After operating 400 h, the π conjugate plane in the FeCl3-g-C3N4 was completely destroyed, and the degradation of BPA was less than 3%. However, the crystal structure of FeCA-g-C3N4 was relatively intact, and the degradation of BPA was still above 90%. According to the XPS and EXAFS spectra, the improvement of the FeCA-g-C3N4 stability was attribute to the shorter lengthen of the Fe–O bond (1.47 Å). Besides, the introduction of electron-rich oxygen center can also effectively promote the reduction of ≡Fe(III) and directly activated H2O2. Additionally, the electron-rich oxygen will also alleviate the shielding effect of halogen ions on the Fe sites, and the low concentration (<0.01 mM) of halide ions could even promote H2O2 activation by 12.2%–24.5%. In conclusion, this study provides new insights to strengthen catalyst stability and accelerate electron transfer in the Fenton-like process, promoting its application in the actual wastewater purification.