Study On The Photoelectrocatalytic Degradation Of Nitrogen-containing Organic Pollutants With ZnO Thin-films Prepared By Sol-gel Method

In this thesis, ZnO thin-film was prepared by sol-gel method to study the photoelectrocatalytic (PEC) degradation of nitrogen-containing organic pollutants,which showed a good photoelectrocatalytic activity .The main contents were described as follows:(1) The ZnO thin film was deposited on conductive glass substrates via the sol-gel method. The ZnO thin film was characterized with electrochemical analysis and some surface analytical methods. The surface morphology and structure were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) . The electrochemical performances were investigated by voltammeter,photo-current response (CA) , and electrochemical impedance spectroscopy (EIS) .(2) The PEC degradation of pyridine over the ZnO film was studied. The results demonstrated that 1.5-h PEC degradation efficiency for 0.36 mmol/L pyridine reached up to 98% under the conditions of 3.00mmol/L H₂O₂, external potential 1.0V, alkali pH. Lower initial concentration could cause faster degradation rate. With the process of pyridine degradation, more and more NH3-N and NO₃-N were produced.The COD removal efficiency for pyridine solution was up to 79.33%.(3) The PEC degradation of p-nitrophenol (PNP) over the ZnO film was studied. The 20-min PEC degradation efficiency for 0.1 mmol/L PNP was up to 99%. The optimum condition was as follows: 7.50mmol/L H₂O₂, external bias potential 1.0V, natural pH (pH=6.13) . The initial concentration of PNP showed inverse effect on the degradation rate. The N elements of PNP were oxidized into NO₃- and the COD removal efficiency was up to 86.01%.(4) The PEC degradation of Methyl Orange (MO) over the ZnO film was studied. The result indicated thatt MO was not effectively degraded by this PEC technology. The optimal condition was as follows:6.00mmol/L H₂O₂, external potential 1.0V, pH3.00.The N elements of MO were turned into NH3-N and NO₃-N. The COD removal efficiency for MO reached to 75.47%.