High-efficiency removal of tetracycline by carbon-bridge-doped g-C3N4/Fe3O4 magnetic heterogeneous catalyst through photo-Fenton process

Carbon-bridge-modified malonamide (MLD)/g-C 3 N 4 (CN) was prepared by copolymerization of MLD with urea and melamine and loaded with Fe 3 O 4 for the high-efficiency removal of tetracycline (TC) in water under photo-Fenton. The prepared catalysts were characterized by SEM, TEM , N 2 adsorption–desorption analysis, XPS, XRD, and FTIR, which proved that the modification method successfully introduced the C bridge into the carbon nitride molecular system and increased the structural defects of the catalyst. The Carbon-bridge-modified MLD/CN/Fe 3 O 4 also had good visible-light response and charge-separation and transport abilities in the photoelectrochemical test. Degradation results showed that the photo-Fenton degradation of TC reached 95.8%, and the mineralization rate was 55.7% within 80 min at 80 mM H 2 O 2 dosage, 0.5 g/L catalyst dosage, and near-neutral pH by 0.8MLD/CN/Fe 3 O 4 . Moreover, the oxidation products and mineralization pathways of TC were explored by LC-MS. Toxicity analysis indicated low environmental threat of the intermediates in TC mineralization. EPR analysis and H 2 O 2 decomposition efficiency analyses showed an improvement in the H 2 O 2 decomposition performance of 0.8MLD/CN/Fe 3 O 4 . This work could provide a valuable insight for the application of heterogeneous photo-Fenton technology in wastewater treatment .