Dual-defect LaFeO3 photo-Fenton removes β-E2 from dairy wastewater

Herein, LaFeO3 photocatalysts (HX-LFO and SX-LFO) were synthesized using hydrothermal and sol–gel methods, respectively, for removing β-E2 from dairy cattle breeding wastewater. A combination of flocculation pretreatment and photocatalytic Fenton oxidation was used to achieve efficient β-E2 degradation. Results revealed that HX-LFO had high defect concentrations and achieved better photocatalytic Fenton oxidation efficiency for β-E2 than SX-LFO. The H0.7-LFO/H2O2/visible (Vis) system completely degraded 2 mg/L of β-E2 within 2 h and achieved a total organic carbon (TOC) mineralization rate of 99.7%. The intermediate products, degradation pathways, and ecological toxicity of β-E2 degradation were analyzed. The H0.7-LFO/H2O2/Vis system exhibited stable degradation performance when humic acid and multiple anions coexisted in the reaction solution. The developed system increased the β-E2 degradation rate to 83.38%–100%. Characterizations and density functional theory calculations revealed that the La-defect formation energy in La/O dual-defect LaFeO3 was lower than that in LaFeO3 containing only La defects. Moreover, O defects facilitated the formation of La defects that lowered the energy barrier for free-radical desorption, making it easier for free radicals to form and diffuse into the reaction solution. La/O dual-defect LaFeO3 exhibited lower binding energy for β-E2, accelerating charge transfer within itself and from itself to β-E2.