Superoxide radical (·O₂⁻)–driven peroxymonosulfate activation via cation-deficient lanthanum ferrite perovskite oxides : Electronic structure modulation for high-efficiency estrogen degradation in dairy wastewater

Estrogen is commonly found in dairy farm wastewater, garnering attention owing to its negative impacts on biological health and the environment. Herein, lanthanum ferrite perovskite oxides (LaFeO3) with La defects were synthesized using the sol–gel and hydrothermal methods for efficient persulfate (PMS)-activated degradation of estrogen and other pollutants. Hydrothermally synthesized La0.7FeO3 (H0.7-LFO) was tailored to produce a large amount of O2−, achieving 100% degradation of β-estradiol (β-E2) with an initial concentration of 2 mg/L within 60 min. The associated degradation rate constant was 22.03 times of that for sol–gel-synthesized La0.7FeO3. The considered H-0.7LFO/PMS system exhibited good degradation performance under various conditions, such as the coexistence of different ions, the involvement of humic acid substances, a wide pH range, and multiple reuses, indicating its excellent stability and reusability. When using the H-0.7LFO/PMS system for dairy farm wastewater, the β-E2 degradation capacity reached 82.16–99.25%, indicating notable potential for practical applications. Characterization analysis revealed that introducing La defects reduced the particle size and the number of abundant formed pores within H0.7-LFO. Further, electron transfer compensated for the involved La defect-induced charge imbalance, accelerating the Fe(III)–Fe(II)–Fe(III) redox cycle and enhancing pollutant degradation.