Study On Electro-Fenton Oxidation Of P-nitrophenol By CoS₂-N/nano-G Gas Diffusion Electrode

P-nitrophenol is widely used in the raw materials or intermediates of dyes,pesticides and preservatives,which is of great significance to people’s production and life.However,when the water containing p-nitrophenol is discharged into the water body,it is difficult to be oxidized and degraded by the water body’s own cleansing function,and pollute the water body.P-nitrophenol is also a highly toxic and carcinogenic substance.Long-term exposure will have side effects on the physiological functions of the human body and affect the endocrine system and cause endocrine system disorders.In this paper,p-nitrophenol,a refractory substance,is used as the research object,and the water samples containing p-nitrophenol are processed by electrochemical advanced oxidation technology.In this paper,a new type of gas diffusion electrode is prepared using foamed nickel as a substrate and using nitrogen and cobalt disulfide to modify nano-graphite.This electrode is used to study the change law of hydrogen peroxide during the reaction and to study the oxidation of this electrode.The process of p-nitrophenol has a major influence on the degradation effect,and the intermediate products of p-nitrophenol degradation under this path are observed.In this paper,three materials of graphite nanometer,N/nano-G and CoS₂-N/nano-G were successfully prepared.All three materials are black powder.After morphological characterization and electrochemical performance characterization,N/nano-G and CoS₂are obtained.CoS₂-N/nano-G has good electrochemical performance,and the performance of CoS₂-N/nano-G is better than that of N/nano-G.Taking the amount of hydrogen peroxide as the criterion for investigation,the best conditions for electrode preparation are as follows:the ratio of electrode material to PTFE is 1:1,and then a small amount of absolute ethanol is added and stirred in a water bath at 37℃to form a paste.Cover the electrode paste on the foamed nickel substrate,without being rolled by a tablet press,put it in a muffle furnace at 350℃for one hour,take it out,soak in acetone for 24 hours,and rinse with deionized water;the best conditions for electrolysis are:The electrolyte is 0.1 mol/L sodium sulfate,the cathode potential is-0.2 V,the electrode spacing is 2.5 cm,the p H is 3,and the air flow rate is300 ml/min.Use the CoS₂-N/nano-G gas diffusion electrode to remove p-nitrophenol.When the iron ion concentration is 0.2 mmol/L and the current density is 20 m A/cm2,the removal of p-nitrophenol has the best effect..Under the same conditions,a cyclic experiment was used to test the electrode stability.The CoS₂-N/nano-G gas diffusion electrode has a removal efficiency of more than 85%for p-nitrophenol after 10 times of use,and the removal rate of TOC is still more than 40%.It shows that the stability of the electrode is better.The intermediate products in the degradation process of p-nitrophenol were determined by UV full-spectrum scanning and liquid-mass spectrometry.After extraction with a solid phase extraction column,the intermediate products were mainly hydroquinone,catechol,and 4-nitro.Six substances:catechol,1,2,4-benzenetriol,p-benzoquinone,and phenol.The possible degradation mechanism is that the nitro group of p-nitrophenol is substituted after being attacked by hydroxyl radicals to form aromatic derivatives such as hydroquinone,catechol and 4-nitrocatechol,which are then Hydroxyl radicals attack and oxidize to generate 1,2,4-benzenetriol and p-benzoquinone,which are then oxidized.