| With synchronistical functions of mild reaction conditions,stable degradation with high efficiency,simple operation,small footprint,wide application,and good environmental compatibility,electrochemical degradation?ECD?technique has been recognized as an effective approach for the purification of phenol containing refractory wastewater.The foremost part of ECD is obviously the availability of electrode materials with high performance and low cost.Tin antimony dimensionally stable anodes have been studied for many years and continue to attract considerable interests due to their good corrosion inhibition and dimensional stability,high oxygen evolution over-potential,good electrical conductivity and catalytic activity,and low preparation cost.In order to further improve the electrochemical activity and stability of SnO2-Sb/Ti electrode,Ag@AgCl and tetra-n-butyl titanate were introduced as a modifier to the solution of tin antimony in view of unique photoelectrochemical properties of Ag@AgCl and TiO2,and Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoanode was fabricated successfully by their modification to SnO2-Sb/Ti electrode.The physicochemical properties of photoanode were studied by using different characterization methods.The catalytic activity of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoanode was evaluated by treatment of simulated wastewater containing phenol.At the same time,the optimum preparation process of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoanode was determined by optimizing the preparation conditions of photoanode.Finally,the preliminary study on degradation mechanism of phenol on the Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoanode was Presented.The main conclusions are as follows:1.Ag@AgCl and tetra-n-butyl titanate were introduced to the solution of tin antimony,and Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoanode was fabricated with thermal decomposition method.SEM-EDS results showed that the surface of the co-modified photoelectrode became more compact and dense,porosity was greatly reduced,and the surface morphology of the electrode was effectively improved.Sn,Sb,Ag,Cl,and Ti had been successfully loaded on the Ti substrate.XRD and XPS measurements show that Sn and Sb exist in the form of+4 and+5 valences of SnO2 and Sb2O5 respectively,Ag@AgCl exists in the form of Ag2O,AgCl and elemental Ag,and Ti exists mainly in the form of TiO2?rutile and anatase?.The electrochemical performance test results show that the exchange current density of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode is4.1267×10-3in a 0.5 mol/L Na2SO4+200 mg/L phenol system,relative to3.3682×10-5for the SnO2-Sb/Ti electrode,which has been significantly improved.Compared with the SnO2-Sb/Ti electrode,the feed current and voltammetry charge of the photoelectrode in the cyclic voltammetry test are improved.The results of the AC impedance spectroscopy show that the Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode has a smaller Warburg impedance than the original electrode.The treatment results from simulated wastewater containing phenol showed that the electrocatalytic oxidation removal efficiency of phenol on Sn-Sb-Ti-Ag/Sn O2-Sb/Ti photoelectrode increased about 23.2%relative to the SnO2-Sb/Ti electrode,and the COD removal efficiency on Sn-Sb-Ti-Ag/Sn O2-Sb/Ti photoelectrode was also significantly higher than that of SnO2-Sb/Ti electrode.The photoelectrocatalytic efficiency of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode is improved by nearly 13.6%compared to its own electroc-atalytic activity,and phenolic organic pollutants degradation on Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode is in accordance with the pseudo first-order reaction kinetics.2.Effects of calcination atmosphere environment,calcination temperature and the additive Ag@Ag Cl dosage on the surface morphology and phase composition,electrochemical performance and phenol catalytic degradation efficiency of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode were studied,and the best preparation process of Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode was confirmed:nitrogen protection environment,calcination temperature 500?and the additive Ag@AgCl dosage 0.2 g.3.Phenol degradation mechanism on Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrode is studied initially with ultraviolet-visible spectrophotometry,hydroxyl radical capture and mechanism discussion.The results of UV-Vis spectrophotometry show that the photoelectr-ocatalytic oxidation of Sn-Sb-Ti-Ag/SnO2-Sb/Ti electrode has higher phenol degradation and mineralization capacity than that of electrocatalytic oxidation.The electrode has specific degradability to the phenolic characteristic absorption peak at 210 nm.Hydroxyl radical capture results show that the hydroxyl radical generation ability is:Sn-Sb-Ti-Ag/SnO2-Sb/Ti photoelectrocatalysis?16.52 mg/L?>Sn-Sb-Ti-Ag/SnO2-Sb/Ti electrocatalysis?11.45 mg/L?>SnO2-Sb/Ti electrocatalysis?9.89 mg/L?.After co-modification with Ag@-AgCl and Ti O2,the electrode hydroxyl radical generation ability was greatly improved,corresponding to stronger phenol catalytic degradation.At the same time,it also shows phenol catalysis degradation on SnO2-Sb/Ti electrode and Sn-Sb-Ti-Ag/SnO2-Sb/Ti electrode is mainly based on indirect oxidation of·OH. |
PDF Full Text Request