Study On Comparation Of Electro-catalytic Characteristics Of Different Ti-based PbO₂ And Impact Factors On Generation Of Hydroxyl Radicals In The Process Of Electrolysis

The material of electrodes is one of the most important parts inelectrochemical oxidation technology. The feasibility, velocity and thereaction degree of subsidiary reaction of organic substances that areoxidized or deoxidize on different electrode materials and catalyzedmaterials are different. Therefore, it is an important question fordiscussion to advance and improve performance of el ectrode material.Lead dioxide electrodes on Ti substrates were pr epared bythermal-deposition and electro-deposition in this paper.Electro-catalytic characteristics of the electrodes prepared by twomethods above were investigated through the degradation experimentsof phenolic wastewater and the amount of hydroxyl radicals, and sothe electrodes mingled with Bi or La prepared by electro -depositionwere, and the effects of additives to electrode structure and catalyticcharacteristics were discussed through SEM and XRD. Theexperimental results showed that the surface of electrodes was smoothand compact, and the crystal-type of electrodes prepared byelectro-deposition was -PbO₂. The additives can improve themicro-structure of electrode surface, reduce inner stress of platinglayer, enhance catalytic activity, and make the c rystals of the platinglayer fine and symmetrical. The four electrodes all ha ve goodelectro-catalytic characteristics, can reduce the voltage, and theelectrochemical degradation of phenol follows one -step reaction dynamics. Electro-catalytic characteristics of the electrodes preparedby electro-deposition were better than the electrodes prepared bythermal-deposition, and the electrode mingled with La was bette r thanthe electrode mingled nothing or with Bi. Electrochemical oxidationcan be divided to direct electrochemical oxidation and indirectelectrochemical oxidation according to the mechanism of electrodesreaction. The catalytic characteristics of electro des and degradation ofphenol are different when the electrodes are prepared by differentmethods or with different additives. The improvement ofelectro-catalytic activity of electrodes makes the ability of directelectrochemical oxidation and indirect electrochemical oxidationstrengthened and the degradation of phenol optimized. The theory onthis need to be consummated more.The method to determine absolute concentration of hydroxylradicals is very difficult because of strong reaction activity, shortlifetime and low concentration of radical, therefore the research onmethods to measure the concentration of hydroxyl radicals ha ve beenattached much importance to on medicine, biochemistry, environmentchemistry, and so on. High performance liquid chroma tograph wasapplied to detect the concentration of the aromatic hydroxylation2,5-DHBA to determine the amount of·OH with 2-HBA as the capturematter. Hydroxyl radicals are one of primary oxidants inelectro-catalytic oxidative reaction, so research on th e impact factorsof hydroxyl radicals has a prodigious theoretic meaning to improve theelectro-catalytic oxidative technics. Power supply, electro -catalytic characteristics of electrodes, current intension, inhibitors andfrequencies in AC power supply on the effects of hydroxyl radicalsgenerated by electrolysis and the degradation of phenol wereinvestigated through the degradation experiments of phenolicwastewater and the amount of hydroxyl radicals generated. Theexperimental results showed that the higher the concentration ofhydroxyl is, the better the degradation of phenol is; the degradation ofphenol with electrodes prepared by electro -deposition is better than theelectrodes prepared by thermal-deposition, the electrode mingled withLa is better than the electrode mingled nothing and with Bi, and theelectrode mingled with La is the best; the degradation of phenol isinhibited when CO₃^2- PO₄^3- or CH₃COO^- exists, and the inhibitingeffect of CO₃^2- is the strongest. AC power supply, electrode with g oodcatalytic characteristics, without inhibitors, strong current intensity andhigh frequency are in favor of the generation of hydroxyl radicals andthe degradation of phenol; DC power supply, electrode with badcatalytic characteristics, with inhibitors, weak current intensity andlow frequency are not in favor of the generation of hydroxyl radicalsand the degradation of phenol.