Study On The Synthesis Of Delafossite Type Oxides And Its Performance Of Activated Peroxymonosulfate

The advanced oxidation technology based on persulfate has good application prospects in the degradation of organic pollutants in dye wastewater.Transition metals and their oxides can effectively activate persulfate to degrade organic pollutants in water,but there are problems such as metal ion dissolution,susceptibility to p H and inorganic anions.To address the above issues,in this paper,CuMn O₂ catalysts were synthesized by hydrothermal reaction method.The effects of different hydrothermal temperature,hydrothermal reaction time,Na OH dosage,different raw materials on the purity and morphology of synthesized CuMn O₂,and the effect of catalyzing PMS to degrade OI were investigated.The optimal synthesis conditions of CuMn O₂ were determined as follows:the reaction temperature was 160℃,the reaction time was 24 h,and the amount of Na OH added was 110 mmol.Under the optimal synthesis conditions,the degradation rate of OI by CuMn O₂ catalyst for 30 min was 77.3%.Different raw materials had no effect on CuMn O₂ catalytic efficiency.It is determined that the optimal conditions for degrading pollutants are neutral environment.The optimal values of catalyst concentration and PMS dosage are 0.10 g/L and 0.10 m M,respectively.The degradation effect decreased after four cycles.This may be due to the small molecule intermediates degraded by OI occupying part of the catalyst surface active sites,and the catalytic degradation effect is reduced.Secondly,CuCr O₂,CuCo O₂,and CuFe O₂ catalysts with different M sites were synthesized（CuMO₂）.XRD,SEM,BET,XPS,electrochemical testing and other characterization methods were used to characterize the crystal structure,surface morphology,specific surface area,surface element composition,and electron transport capacity of different M-site delafossite-type catalysts.The effects of the four catalysts on the degradation of OI are as follows:CuFe O₂<CuMn O₂<CuCo O₂<CuCr O₂.And the adsorption effect on OI was basically the same.Taking the CuCr O₂/PMS catalytic system as an example,the effects of the concentration of PMS,the amount of catalyst,and the initial concentration of the solution on the degradation performance were discussed.The effect of the initial p H of the solution shows that CuCr O₂ catalyst can catalyze PMS degradation of organic dye OI over a wide p H range,and has good degradation effect.The anion effect experiments showed that H₂PO₄^-and HCO₃^-also had a certain inhibitory effect on CuCr O₂/PMS system,Cl^-had little effect on the removal efficiency of OI,and HA had a slight promotion effect on the degradation of OI.Dissolution and cycling experiments shown that the concentration of the metal dissolved in the catalyst in the catalytic system was lower than the emission standard of metal ions in the water.After four cycles,the catalyst still has a strong ability to degrade OI.It shown that its structure and surface properties are stable.Finally,through the surface hydroxyl site testing,electrochemical analysis,quenching experiments,and in-situ characterizations such as ATR-IR and ESR,the mechanism of the four catalysts catalyzing the degradation of OI by PMS was discussed.First,Cu⁺/M³⁺is used as the Lewis site,which is combined with H₂O to form Cu⁺/M³⁺-OH.Then Cu⁺/M³⁺-OH-HSO₅^-is formed by the hydrogen bond and HSO₅^-.For CuCr O₂ and CuMn O₂,Cu⁺reacts with HSO₅^-adsorbed on the catalyst surface to selectively generate hydroxyl radicals（·OH）;For CuCo O₂ and CuFe O₂,Cu⁺reacts with HSO₅^-adsorbed on the catalyst surface and selectively generate sulfate radicals(SO₄^·-),then generate various free radicals(O₂^·-、¹O₂ and·OH),and interact with the dye molecules to degrade them into small organic intermediates,and even CO₂ and H₂O.