Study On Electrochemical System For Reductive Defluorination Of 4-Fluorophenol

4-fluorophenol(4-FP)is one of the typical representatives of fluorinated aromatic hydrocarbons.It is widely used in the production of pharmaceutical and agrochemical intermediates.At the same time,it is also generally environmentally persistent and poses a threat to human and biological health.Effective removal of 4-FP in water is important to reduce environmental pollution.The electrochemical reduction method can remove the fluorine atoms in 4-FP under milder and easierto-handle conditions,reducing its chemical and biological stability,and facilitating subsequent degradation by chemical oxidation or biodegradation methods.In this study,the electrochemical system was used to study the reductive defluorination of 4-FP as the target pollutant,mainly including electrode preparation,construction and optimization of electrochemical reaction system,investigation of reaction influencing factors,and investigation of reaction process.First,after preliminary experiments,a composite electrode based on nickel foam and rhodium and palladium as the plating metal was selected as the reaction electrode.Based on the electrochemical reduction and defluorination of electrode pair 4-FP and the characterization of electrode micro-characterization,the electrodeposited rhodium-supported nickel foam(Rh / Ni)electrode was further optimized.The electrode has good reduction defluorination effect and electrochemical stability,good adsorption and desorption performance,and large specific surface area.The surface of the electrode has a high content of rhodium atoms,which is mainly in the form of Rh(111).,Has shown good electrocatalytic performance in electrochemical reactions.Subsequently,a better electrochemical reaction system was studied and the effects of various reaction conditions on 4-FP electrochemical reduction defluorination were investigated.The results show that the electrochemical reaction system using an electrodeposited rhodium-supported foamed nickel electrode,a two-phase electrolytic cell,a platinum plate anode,and a Nafion117 proton exchange membrane can remove 100% of 4-FP in 3 h,and the defluorination rate is greater than 95%.The constant-voltage electrolysis potential for the electrochemical reaction to achieve 4-FP reduction defluorination should be-3 to-6 V.The concentration of rhodium plating deposit was chosen to be 0.5 mmol / L.4-FP reduced defluorination works better under acidic or alkaline conditions.The removal effect and defluorination rate are best when the solution p H = 3;the removal effect and defluorination rate are poor under neutral conditions.The removal rate and defluorination rate of 4-FP increased with increasing temperature.The electrochemical defluorination rate of 4-FP decreases with increasing substrate concentration.The investigation of the 4-FP electrochemical reduction defluorination reaction process shows that 4-FP electrochemical reduction reaction is a series of hydrogenation and defluorination processes.First,4-FP and hydrogen are adsorbed on the electrode surface to form their adsorption state.It reacts and removes a fluorine to generate phenol anion and fluoride ion,thereby realizing the 4-FP electrochemical hydrodefluorination process.The electrochemical reduction products are mainly phenol,cyclohexanone,cyclohexanol and fluoride ions.The reaction path is 4-FP?Ph?CYC.ol?CYC.one.