Study On The Photoelectrocatalytic Degradation Of Phenol On Immobilized TiO₂

In this paper, immobilized TiO2 thin film was prepared by coating technique and was characterized by XRXK SEM and electrochemical impedence. A 250W UV lamp (365nm) was used as light source. The photoelectrochemical system consisted of three electrodes: immobilized TiOa thin film was used as the working electrode, Cu plate as the counter electrode and saturated calomel electrode as the reference electrode. One of the most typical and difficultly degradated aromatic compounds?phenol was the objective substance. The photoelectrocatalytic degradation of phenol on the immobilized TiO2 thin film was studied. The effects of some factors such as bias, initial pH value of solution, light intensity, initial concentration of phenol, thickness of thin film on the degradation rate of phenol were also investigated. The possible intermediates and the effects of O2 and metal ions (Fe3+ and Cu2+) as electron acceptors respectively were also studied. In this paper, the concentration of phenol was determined by a spectrophotometer; theTOC value (mineralization of phenol) was determined by TC analyzer; the photoelectrocatalytic degradation characteristic of phenol was analysed by UV-VIS and the possible intermediates in the degradation process were determined by GC-MS. The results indicated :Compared with traditional immobilized TiO2, the advantages of the coating technique are: simpler technology, lower-priced and easier to control the crystal phase and so on. The TiOi in the thin film is anatase. An excellent photoelectrocatalytic property is investigated, which could degradate phenol in aqueous solution effectively.In our experimental conditions, the photocatalytic and photoelectrocatalytic degradations follow apparent first-order reaction kinetics. The rate of photoelectrocatalysis is quicker than that of photocatalysis, which is much quicker than that of photoxidation.The phenol degradation rate with anodic bias is quicker than that with cathodic bias. With the increasing anodic bias, light intensity, initial concentration of phenol in solution and thickness of film, the rates of photoelectrocatalytic degradation increase. But there exist the optimal conditions. The optimal initial pH value of photoelectrocatalytic degradation is 3.The possible intermediates in the photoelectrocatalytic degradation arepropene, butene, propane, ethanedioic acid, butanedioic acid etc.With O2 as the electron acceptor the reaction rate of degradation is improved greatly. Due to Fe3+ and Cu2+ have more positive reduction potential, they can also capture photoelectron and improve the degradation rate, while the concentration of Fe3+ and Cu2+ in solutiondecrease. This conclusion is very important for the treatment of wastewater not only containing organic pollutants but also containing inorganic ones.However the reaction rate with Fe3+ and Cu2+ as electron acceptors are slower than that with O2 as electron acceptor. This result is related to the great oxidative capability of ?OH from the reduction of O2.