Improved degradation of tetracycline, norfloxacin and methyl orange wastewater treatment with dual catalytic electrode assisted self-sustained Fe2+ electro-Fenton system: Regulatory factors, mechanisms and pathways

• PbO 2 /SnO 2 and Ag@ZOF catalytic electrodes were prepared by electrodeposition and reduction. • Dual catalytic electrode assisted electro-Fenton system exhibited high degradation efficiency for TC, NOR and MO. • Mechanism of organic degradation by electric-Fenton system was proposed. The environmental hazards associated with the presence of antibiotics and dyes in water sources require the development of efficient and appropriate wastewater treatment technologies. In the research, a dual catalytic electrode assisted self-sustained Fe 2+ electro-Fenton system was constructed to degrade tetracycline, norfloxacin and methyl orange in wastewater efficiently and economically. The novel titanium mesh based PbO 2 /SnO 2 anode electrode was prepared by electrodeposition with the best oxidation performance at the ratio of Sn to Pb 0.5:1, and silver doped Zinc-based organic framework (Ag@ZOF) mixed crystal cathode catalyst was synthesized by precipitation at room temperature. Meanwhile, a sacrificial iron anode was introduced into the system in an acidic solution without a power supply, realizing the endogenous supply of Fe 2+ . The results indicated that the process was capable of self-supporting H 2 O 2 and Fe 2+ under the optimized conditions of pH range of 3.5–4.0, iron area of 10 cm 2 and current intensity of 9 mA. The current efficiency was calculated to be as high as 369.5%. The type of conductive substrate supported cathode catalyst is an important factor determining the performance of the novel coupled electric-Fenton system. Electro-Fenton system using Ag@ZOF catalytic electrode loaded with conductive substrates (stainless steel mesh (SS), carbon felt (CF), and activated charcoal granules (ACG)) was constructed to degrade tetracycline (TC), with the degradation efficiencies of 100% (k = 0.03048), 99.7% (k = 0.01831), 99.7% (k = 0.01421). Moreover, the experiment group of Ag@ZOF-SS electrode had achieved good degradation effects for TC, norfloxacin (NOR), methyl orange (MO), and the degradation efficiency was 99.1%, 92.8% and 100%, respectively. The possible degradation pathways of TC, NOR and MO were proposed by analyzing the intermediates. This work demonstrates the scaling-up potential of the system in the treatment of antibiotics and dye wastewater.