Removal Of Bisphenol A By Activation Of Persulfate With Oxygen Vacancy-rich Fe-co Composite Catalyst

Based on the synergistic effect of different metal ions,Fe-Co composite catalysts can enhance the catalytic activity to persulfate.The introduction of oxygen vacancies to catalysts can promote the redox recycle between different metal valence states and improve the catalytic efficiency.Layered double hydroxides（LDHs）catalysts can broaden the pH adaptation range of the catalytic system.This research innovatively introduced the oxygen vacancies to Fe-Co composite catalysts,and synthesized bimetallic catalysts with spinel structure and LDHs structure.These catalysts were used to activate persulfate and degrade Bisphenol A（BPA）in water.The activation mechanism of catalytic systems and degradation pathways of BPA were also investigated.A Fe-Co precursor was prepared by a sol-gel method,and then calcined in hydrogen atmosphere to obtain the oxygen vacancy-rich Fe-Co composite catalysts.The characterization results showed that the catalyst was spinel structure with abundant oxygen vacancies.The oxygen vacancy-rich Fe-Co composite catalysts were used to activate permonosulfate（PMS）to degrade BPA.The BPA removal rate of 200-HCFO/PMS system was 98%,and the pH adaptation range of the system was wide（3-11）.The main free radicals in the system were SO₄^·-and·OH,and the catalytic degradation reaction was mainly occurred on the catalyst surface.Oxygen vacancies could not only react with dissolved oxygen to produce ¹O₂ and O₂^·-,but also promoted electron transfer in the system.This further promoted the redox cycle between Co³⁺/Fe³⁺and Co²⁺/Fe²⁺,thereby improving catalytic efficiency.Surface hydroxyl groups played an important role in the activation of PMS.The presence of surface hydroxyl groups could broaden the pH adaptation range of PMS catalytic system.Furthermore,the oxygen vacancy-rich Fe-Co composite catalysts were used to activate persulfate（PS）to degrade BPA.The removal rate of BPA by the200-HCFO/PS system was 98%.But the pH adaptation range of this system was narrow（3-7）.The catalytic mechanism of oxygen vacancy and free radicals in the200-HCFO/PS system were similar to the 200-HCFO/PMS system.However,the interaction between surface hydroxyl groups and PS was weak in 200-HCFO/PS system,resulting in the narrow pH adaptation range of this system.For further broaden the pH adaptation range of the Fe-Co catalyst/PS system,oxygen vacancy-rich Fe-Co LDHs were prepared.The characterization results showed that the catalysts had high concentration of oxygen vacancies and surface hydroxyl groups,and had strong electrochemical and optical properties.The removal rate of BPA in Fe₂Co₁-LDH/PS system was 99.67%.A large number of surface hydroxyl groups in the layered structure of LDHs catalyst strengthened the interaction between surface hydroxyl groups and PS.This made the Fe₂Co₁-LDH/PS system has a wide range of pH adaptation（3-11）.And in the acidic and neutral states,the PS was mainly activated by metal ions on the surface of Fe₂Co₁-LDH and produced SO₄^·-for BPA degradation.Under alkaline conditions,BPA was mainly degraded by the·OH generated due to the synergy between oxygen vacancies,surface hydroxyl groups,and transition metals.