Research Of The Lead Oxide DSA Preparation And Electrocatalytic Degradation Of Phenol Wastewater

There are many serious environmental pollution problems in China, especially water pollution problems. Industrial wastewater is the main source of water pollution, and these industrial wastewater contains a large number of biological refractory organic compounds. The preparation of ionic liquids modified PbO₂ electrodes were investigated in this paper. Effects of electrolytic conditions on the formation of ·OH（hydroxyl radical） and COD removal rate of phenol wastewater were studied. The intermediate product and the process mechanism of phenol wastewater in the degradation were investigated at the same time.PbO₂ electrodes modified by 5 kinds of different imidazolium-based ionic liquids and unmodified PbO₂ electrode were prepared by electrodeposition. The surface morphology, elemental composition, crystal structure, surface contact angle and the oxygen evolution potential were characterized by the modern testing methods like SEM, EDS, XRD, contact angle measurement, anode polarization curve measurements, and cyclic voltammetry curve analysis. The results showed that the preferred orientation and surface topography of crystals were affected by the characteristic adsorption of ionic liquid anion. The PbO₂ crystal nucleation and growth rate were affected by the different chain carbon number of imidazole cationic substituent, thus affecting the grain size of electrodeposit. The PbO₂ electrode modified by ionic liquid has smaller contact angle, better surface wettability, higher oxygen evolution potential than that of the unmodified PbO₂ electrode. The PbO₂ electrode modified by ionic liquid is more difficult to take place oxygen evolution reaction in the electrochemical reaction, which has a higher electrocatalytic ability than the unmodified PbO₂ electrode. The surface reaction reversibility of PbO₂ electrode were greatly improved by the addition of the ionic liquid except for the [Emim]Br. With the same time, the stability of ionic liquid modified PbO₂ electrode were greater than the unmodified PbO₂ electrode. The modification effect of ionic liquid with the anion of BF4-is more prominent than the anion of PF6-and Br-, and the modification effect of [Bmim]BF4 is the best.The phenol removal, COD removal and the generation of ?OH in electrochemical system were detected, the dynamic analysis has been investigated at the same time. The electrocatalytic activity of different electrodes was compared, and the stability of different PbO₂ electrodes was studied. The results showed that the phenol removal of different PbO₂ electrodes was not much difference, but the COD removal and the generation of ?OH from ionic liquid modified PbO₂ electrodes was significantly higher than that of the unmodified PbO₂ electrode. It shows that the electrocatalytic activity of the modified electrodes is higher. The dynamic analysis showed that the removal rates of phenol from different PbO₂ electrodes were as follows: [Bmim]BF4 > [Emim]BF4 > [Hmim]BF4 > [Emim]PF6 > [Emim]Br> unmodified electrode, the COD removal rate and the generation rate of ?OH had the same rule with it, suggesting that electrochemical degradation of phenol is mainly attributed to the indirect oxidation by ?OH electro-generated.The electrocatalytic properties of metal oxide electrodes, metal electrode and nonmetal electrode were compared. The effects of electrolyte temperature, current density and impulsing power source on the COD removal and the generation of ·OH in electrochemical system were studied. The results showed that the electrocatalytic performance of metal oxide electrodes（PbO₂ electrode and Sn O₂ electrode） is better than that of metal（Pt） electrode and nonmetal graphite electrode, and the electrocatalytic performance of PbO₂ electrode is obviously better than that of Sn O₂ electrode. The COD removal and the generation of ?OH decreased with the increase of the temperature of the electrolyte. With the increase of the current density, the COD removal of phenol wastewater and the generation of ?OH increased gradually. The average current efficiency of the impulsing power source is higher than that of the DC power supply, that is, less energy consumption, but in the case of the same COD removal rate, the required reaction time is longer.The degradation process of phenol was analyzed by HPLC, and the main intermediate products were detected. The results showed that the phenol electrocatalytic oxidation reaction would generate intermediate like Para Benzoquinone, Maleic acid, Resorcinol and Catechol, then further inorganic.