Engineered design of MnFe2O4/CoNiFe-LTH/g-C3N4 heterocatalyst for doxycycline degradation via Fenton oxidation process: Optimization and mechanism

The removal of organic contaminants from waterways is vital to the ecosystem. A novel MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 catalyst was synthesized via self-assembly preparation, and linked with H 2 O 2 for the Fenton degradation of doxycycline (DXY). The MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 was characterized using FTIR, XRD , XPS, VSM , SEM, TOC, GC–MS, and ICP-OES. Interestingly, the magnetically separable and high-stability catalyst achieved 89.11 % DXY degradation, and 69.30 % TOC removal efficiency within 60 and 120 min, respectively (at pH = 7.5, catalyst dosage= 0.01 g, H 2 O 2 = 400 ppm, T = 20 °C, and DXY concentration= 100 ppm). In addition, the synergistic effect of metal cations (Co, Ni, Fe, and Mn) triggered Fenton degradation through a continuous closed cycle of electrons. A pseudo-first-order kinetic model also fitted DXY degradation with MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 . Furthermore, the radical pathway mechanism was confirmed with XPS before and after degradation, and with radical scavenging tests. The DXY degradation pathway was speculated by GC–MS analysis. Quantitative structure-activity relationship (QSAR) was applied to assess intermediates for developmental toxicity . The MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 catalytic activity on H 2 O 2 decomposition was determined via titrimetric analysis. Recycling tests and ICP-OES measurements were further used to investigate the catalyst's resilience and reusability. Besides, MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 demonstrated a performance of 70 % over eight catalytic degradation runs with minimal metal leaching. Eventually, MnFe 2 O 4 /CoNiFe-LTH/g-C 3 N 4 is a viable catalyst for breaking down organic contaminants in wastewater.