Study On The Formation Of Hydroxyl Radicals In The Electro Catalytic System Of BDD Electrode

Boron doped diamond(BDD)electrode has the characteristics of high oxygen evolution potential,adsorption inertia and good physical and chemical stability.It possesses more superiority than traditional electrodes,and thus it might be very promising in advanced treatment of organic wastewater.The strong oxidation ability of BDD electrode is mainly attributed to the hydroxyl radicals,which can degrade organics efficiently,and occupy an important position in the electro catalytic system.So it is necessary to study the formation and to optimize the production of hydroxyl radicals,which has great significance for improving the electro catalytic efficiency and reducing the energy consumption.BDD electrode was prepared by hot flame chemical vapor deposition(HFCVD)and characterized by XRD?SEM and Raman.It was sealed in the electrolytic cell,and the water cycle is introduced to construct electro catalytic system.Compared with beaker,found that the strong oxidation of phenol is owed to hydroxyl radicals in the electro catalytic system of BDD electrode.Through the method of indirect detection,the hydroxyl radicals were successfully detected in the electro catalytic system of BDD electrode and beaker.Found that the concentration of hydroxyl radicals in the electro catalytic system of BDD electrode is greater than in the beaker.The performance of electro catalytic system is evaluated,which is a good foundation for optimizing hydroxyl radicals.The effect of current density,pH value and Na2SO4 electrolyte concentration on hydroxyl radical was investigated.Through the single factor experiments,the best reaction range of parameters was achieved.The current density was 60--100 mA/cm2,the pH value of the solution was 7--11,the concentration of Na2SO4 was 0.06--0.1 mol/L.Through response surface method,the two regression model between the concentration of hydroxyl radicals(dependent variable)and current density,pH,Na2SO4 concentration(independent variables)was established.According to the response surface,the influence of current density,pH value of solution and Na2SO4 electrolyte concentration on hydroxyl radicals were analyzed.Under the condition of current density 100 mA/cm2,pH value 9,the Na2SO4 concentration 0.1 mol/L,the greatest concentration of hydroxyl radicals was achieved.The effect of ultrasonic on the hydroxyl radicals of BDD electrode was investigated.Experiments show that when the current density was less than 60 mA/cm2,with the increase of the current density,the effect of ultrasonic on the concentration of hydroxyl radicals gradually becomes small.When the current density was exceed 60 mA/cm2,the ultrasonic has little effect on hydroxyl radicals.Under the condition of current density 60 mA/cm2,increased the ultrasonic power,the effect of ultrasonic on the concentration of hydroxyl radicals could be further improved.