Surface dielectric barrier discharge coupled with a biochar/Fe/TiO2 photo-Fenton catalyst for efficient degradation of methylene blue in water

Textile dye wastewater is difficult to treat because of its complex composition, chemical sta bility, and poor biodegradability. In this study, a comb-electrode surface dielectric barrier discharge (SDBD) process was coupled with a biochar-supported Fe species/TiO2 composite catalyst (TFCF) for methylene blue (MB) degradation. TFCF was prepared by pyrolysis, im pregnation, and sol-gel treatment and characterized using SEM, XRD, FT-IR spectroscopy, Ra man spectroscopy, XPS, photocurrent response, and electrochemical impedance spectroscopy. Fe species and TiO2 were uniformly anchored on the biochar matrix, forming Ti-O-Fe interfa cial bonds. Under the optimized conditions of a 2.0 g L−1 catalyst dosage, 12 kV peak-to-peak voltage, and 200 mL min−1 air flow rate, the SDBD/TFCF system removed 94.31% of MB (100 mg L−1 ) within 30 min, with an energy efficiency of 0.613 g kWh−1 and an apparent rate constant of 0.09039 min−1 . The rate constant was approximately four times that of plasma treatment alone. Mechanistic analysis showed that biochar promoted electron transfer and 1 Fe3+/Fe2+ cycling, whereas TiO2 photocatalysis and heterogeneous Fenton reactions generated abundant oxidizing species. Hydrated electrons and ·OH were the dominant active species. After five reuse cycles, MB removal decreased by only 13.86%, while the catalyst structure remained stable. Seed-germination assays confirmed a marked reduction in biotoxicity. The system also efficiently removed methyl orange, acid orange, reactive blue 19, RBE, and rho damine B, demonstrating broad applicability to dye wastewater treatment.