Enhanced Sulfamethazine Degradation over a Wide pH Range by Cost-Effective Zero-Valent Iron-Based Electro-Fenton/Sulfite Process

Sulfamethazine (SMT) is an antibiotic with good antimicrobial effect and is widely used to treat human and livestock diseases. Though the degradation of SMT by the conventional Fenton and electro-Fenton (EF) processes is efficient, it is limited by a narrow pH and iron sludge generation. Herein, we constructed a cost-effective EF system with the synergistic effect of zero-valent iron (Fe0) and sulfite (Fe0-EF/Sulfite), and key parameters such as applied current, catalyst dosing, sulfite dosage, and initial pH were optimized. Under the optimal conditions (Fe0 dosing of 50 mg/L, sulfite dosage of 1.5 mM, current of 40 mA, and pH of 3), the removal efficiency of 10 mg/L SMT reached 100% within 30 min, and the degradation rate constant reached 0.194 min−1. Electron paramagnetic resonance (EPR) analysis and quenching experiments confirmed the generation of various reactive oxygen species (ROS), such as •OH, SO4−, O2−, and 1O2, which significantly improved the pollutant removal efficiency. Sulfite accelerated iron cycling and inhibited the formation of iron sludge, thus broadening the pH range of the reaction from three to eight and overcoming the limitations of the conventional EF process. The Fe0-EF/Sulfite system performs cost-effectively at a wide pH range, providing an efficient and low-carbon solution for environmental pollution remediation with broad application prospects.