Construction Of Alkaline Electro-fenton Reaction Based On Electrochemical Oxidation Of Water To Synthesize H₂O₂

Electro-Fenton technology combines the characteristics of electrochemical reduction of O₂ to synthesize H₂O₂ and traditional Fenton reaction,which uses iron ions to activate H₂O₂ to generate highly active free radicals.It has been widely used to treat industrial organic wastewater,and has the advantages of simple operation,high reaction efficiency and less secondary pollution.However,the traditional electro-Fenton technology is only used to treat acidic organic wastewater,and cannot degrade alkaline organic wastewater,because its cathodic electrochemical synthesis and activation of H₂O₂ can only be realized in acidic environment.In actual production and life,there are a large number of alkaline organic wastewater to be treated urgently,so it is necessary to explore and develop electro-Fenton reaction technology suitable for alkaline environment.Aiming at the limitation that traditional electro-Fenton technology is only suitable for treating acidic organic wastewater,according to the nature that Fenton reaction is mainly driven by H₂O₂ activation and·OH,and the characteristics of alkaline electrochemical oxidation of water to synthesize H₂O₂,this paper put forward a method to construct an alkaline electro-Fenton reaction to effectively degrade organic pollutants in water,and systematically studied the reaction law and function of this alkaline electro-Fenton system.The main research contents and conclusions were as follows.（1）In₂O₃ thin film was prepared on the surface of FTO conductive glass by direct drop coating.Using the stable physical and chemical properties of In₂O₃ thin films,H₂O₂ was synthesized by driving H₂O oxidation in KHCO₃ electrolyte,which was used to construct an alkaline electro-Fenton reaction system.The results show that as anode material,In₂O₃ thin film could drive oxidation water to synthesize H₂O₂ in KHCO₃ electrolyte.In addition,the In₂O₃ thin film anode could stably oxidize water to synthesize H₂O₂;After reaction for 12 h,the crystal structure and micro-morphology of In₂O₃thin film remained basically unchanged.Mn O₂nanorods were added to the reaction system of electrochemical oxidation of water to synthesize H₂O₂ by anodic oxidation of In₂O₃ thin film,which could catalyze the conversion of H₂O₂ generated by activation into·OH,and reached the basic conditions for constructing an alkaline electro-Fenton reaction system.The working principle of alkaline electro-Fenton reaction system based on anode of In₂O₃ film is as follows:in KHCO₃ electrolyte,HCO₃^-is firstly oxidized to HCO₄^-on the anode of In₂O₃,and then HCO₄^-reacts with H₂O in the electrolyte to oxidize it to H₂O₂,and itself is reduced to HCO₃^-,completing the conversion cycle of HCO₃^-/HCO₄^-;At the same time,under the catalytic activation of Mn O₂,H₂O₂synthesized by electrochemical reaction is converted into·OH,which had the potential activity of degrading organic pollutants in alkaline aqueous solution.（2）Taking the alkaline aqueous solution containing PNP,Rh B and BPA as the treatment object,the law and mechanism of degradation of organic pollutants in water by anodic alkaline electro-Fenton reaction system of In₂O₃ film and anodic alkaline electro-Fenton reaction system of graphite sheet were systematically explored.It was found that PNP,Rh B and BPA organic pollutants could be effectively degraded in the anodic alkaline electro-Fenton reaction system of In₂O₃ thin film.The co-existence of anions such as Cl^-,NO₃^-and SO₄^2-in water had little effect on the degradation activity of organic pollutants in water by anodic alkaline electro-Fenton reaction system of In₂O₃ film.Organic pollutants such as PNP,Rh B and BPA could also be effectively degraded in graphite anode-based alkaline electro-Fenton reaction system.The factors such as KHCO₃ concentration,DC voltage,electrode area and Mn O₂ content had important influence on the degradation activity of the system,and the order of influence was KHCO₃ concentration>DC voltage>electrode area>Mn O₂ content.Under the optimum degradation conditions,the graphite anode-based alkaline electro-Fenton reaction system could efficiently degrade 100 ppm PNP,Rh B and BPA simulated wastewater prepared from tap water.In the two basic electro-Fenton reaction systems,the main active species for degrading organic pollutants in water is·OH,which was mainly generated by Mn O₂ catalytic activation of electrochemically synthesized H₂O₂.The basic electro-Fenton reaction system constructed in this paper could make up for the deficiency that the traditional electro-Fenton reaction was only suitable for degrading acidic organic wastewater,and could also provide useful experimental parameters,construction methods and reaction theoretical reference for developing electro-Fenton reaction technology suitable for alkaline environment.