The Studies On Preparation Of Graphene Supported Manganese Compounds And Catalytic Ozonation Of Phenol

Ozone oxidation is a kind of advanced oxidation process.But ozone oxidation reaction is selective and slow reaction rate.Heterogeneous catalyticozonation has attracted more and more attention for its high efficiency of the ozone,the excellent extent of the oxidation of the organics and efficient removal of refractory organic compounds.Phenolic pollutants with high toxicity and carcinogenicity has a wide variety of sources.The study about efficient removal of phenol pollutants has great practical significance.Graphene,which has excellent chemical stability,electrical conductivity,large specific surface area and other characteristics,is still relatively rare in the combination of ozone and graphene.Therefore it has great potential in the field of catalytic ozonation.Graphite oxide was synthesized by a modified Hummers method.Then graphite oxide wasused to synthesize graphene supported manganese dioxide,graphene supported manganese phosphateand,graphene supportedferriferrous oxide and manganese dioxideby hydrothermal synthesisusing hydrazine hydrate as the reducing agent.The prepared materials were characteriazed by several characterization methodsrespectively,followed by studies of application in the ozonation of phenol.The effects of catalyst dosage,initial pH,addition of tert-butanol,the change of pH and the number of recycle of catalyst were studied.The reaction mechanism of heterogeneous catalytic ozonation of phenol was further investigated.The characterization results of MnO₂/RGO showed that the spherical MnO₂ particles have been successfully supported on reduced graphene oxide.In MnO₂/RGO/O₃ system,the adsorption of phenol by MnO₂/RGO and RGO is very small.RGO has almost no catalytic activity for phenol.When pH was 3,the removal rate of phenol by catalytic ozonation was increased by 97.7% compared to ozonation alone.The removal of phenol was positively correlated with catalyst dosage.The removal rate of phenol increased with the increase of the concentration of ozone and the pH of solution.The pH value of solution will get smaller with the increase of the reaction time.The tert-butanol experiments showed that the surface of the catalyst and the solution were all related to the free radical mechanism.Furthermore,the surface reaction plays an important role in the process of MnO₂/RGO catalytic ozonation of phenol,which indirectly proved by experiments of the influence of initial pH and the change of pH during the reaction.The characterization results of Mn₃?PO₄?₂/RGO showed that the Mn₃?PO₄?₂particles have been successfully supported on reduced graphene oxide and Mn₃?PO₄?₂is the amorphous forms.In Mn₃?PO₄?₂/RGO/O₃ system,the addition of Mn₃?PO₄?₂/RGO has greatly improvedthe removal of phenol.The removal of phenol was positively correlated with catalyst dosage.The removal rate of phenol increased with the increase of the pH of the solution and the reaction temperature,but when the temperature was too high,the phenol removal rate will decline rapidly.When pH was 3,the removal rate of phenol by catalytic ozonation was increased by 135.4% compared to ozonation alone.The pH value of solution will get smaller with the increase of the reaction time.The tert-butanol experiments showed that the catalytic ozonation of phenol was followed by a hydroxy free radical mechanism,which indirectly proved by experiments of the influence of initial pH and the change of pH during the reaction.The phenol was mainly oxidized by thehydroxyl free radical.The characterization results of MnO₂/Fe₃O₄/RGO showed that the MnO₂ and Fe₃O₄ particles have been successfully supported on reduced graphene oxide.The addition of MnO₂/Fe₃O₄/RGO has greatly improved the removal of phenol.The removal rate of phenol increased with the increase of the pH of the solution.When pH was 3,the removal rate of phenol by catalytic ozonation was increased by 115.4% compared to ozonation alone.The magnetic separation tests showed MnO₂/Fe₃O₄/RGO can be separated from the solution quickly by a magnet.The tert-butanol experiments showed that the catalytic ozonation of phenol by MnO₂/Fe₃O₄/RGO was followed by a hydroxy free radical mechanism.