Study On The Treatment Of Phenol Wastewater By Heteroge-neous Catalytic Oxone

Advanced oxidation technologies based on the generation of sulfate radicals?SO₄^·?have emerged over the past years as a promising technique to degrade completely most organic pollutants.Commonly used cobalt activated persulfates produce sulfate radicals was used,although the efficiency of homogeneous catalysis is high,but cobalt ions are toxic.So cobalt must be supported on the carrier.In this study,Co?NO₃?₂·6H₂O and Fe?NO₃?₃·9H₂O were used as precursors.The transition metal cobalt and iron were immobilized on the TiO₂ support by impregnation and precipitation to prepare a new composite catalyst CoFe/Ti0₂,catalyzing and activating the oxone to form strong oxidizing free radicals SO₄^·and · OH to degradation phenol wastewater.The effects of cobalt-iron loading and calcination temperature on the degradation efficiency of CoFe/Ti0₂ catalyst were investigated and the characterization analysis and stability test were carried out.The effects of initial pH,catalyst dosage,oxidant dosage,reaction temperature and light conditions on the degradation of phenol wastewater from CoFe/TiO₂ heterogeneous catalytic oxidation oxone system were investigated.The reaction processes of the sulfate radicals and hydroxyl radicals produced by catalytic activation of oxone by CoFe/TiO₂ and the reaction mechanism of phenol attack were discussed.Concluded as follow:?1?CoFe/Ti0₂ was prepared by impregnation and precipitation method using Ti0₂ as carrier.The optimum preparation process was as follows:CoFe/Ti0₂ with Co and Fe load ratio of 1:1 and total load of 70%;the optimum calcination temperature was 500?.The prepared TiO₂ and CoFe/Tio2 composites were tested by SEM,BET,XRD and XPS.The results show that cobalt and iron have been successfully supported on supported TiO₂,and the loading of cobalt and iron has an effect on the structure of Ti0₂,the specific surface area and pore volume of the carrier were reduced.The cobalt and iron supported on Ti0₂ were mainly in the form of CoFe₂O₄,and part of Fe₂O₃.After 3 cycles of CoFe/Ti0₂ still maintain high catalytic activity,and only a trace of cobalt ions and iron ions dissolved,can be safe to use.?2?The influencing factors on the degradation of phenol wastewater by heterogeneous CoFe/TiO₂/Oxone catalytic oxidation system show that the removal efficiency of phenol by CoFe/TiO₂ catalyzed by the catalyst under neutral conditions was the best.The optimum conditions were as follows:under the condition of UVB irradiation,the reaction temperature was 35?,the best dosage of catalyst CoFe/TiO₂ was 1.5 g/L,the best dosage of oxidant oxone was 3 g/L.At this point,the phenol wastewater removal rate can reach 93.1%.?3?The physical and chemical structure of CoFe/TiO₂ before and after the reaction showed that the damage of the catalyst structure under UVB light was larger than that without light,and its basic composition did not change before and after the reaction,indicating that the catalyst did not participate in the degradation reaction,the degradation kinetics of phenol in CoFe/TiO₂/Oxone system under UVB irradiation is in accordance with the quasi-first order kinetic model.The study on the change of free radicals showed that the main oxidation effect of SO₄^· free radicals.The main oxidation of this experimental system is SO₄^· radical,Under the attack of SO₄^·radical,the aromatic ring of phenol generated the carbon centered free radicals by the electron transfer,further the intermediate was formed,which was oxidized into small molecules of organic acids by SO₄^· and finally be mineralized into CO₂ and H₂O.