Preparation Of Doped Ti/TiO₂-SnO₂ Composite Electrode And Its Application In The Treatment Of Oil-field Wastewater

This thesis focused on the preparation of rare earth La and Ce doping Ti/TiO2-SnO2 composite electrode and investigation on its characteristics. The oil-field wastewater was taken as the model substrate, and the optimization of degradation process was studied.In this text, Ti/TiO2-SnO2 composite electrodes were prepared by Sol-Gel method. On the basis of analysis of the O2 evolution potential and the degradation of washing sewage, the optimal ratio of titanate and stannic was assured (Ti:Sn=100:10). Rare earth-doped method was taken to further improve the catalytic performance of composite electrode. The temperature and time of thermal treatment and the doping amount of rare earth were studied in detail, which had great influence on the characteristics of electrodes. The preparation conditions of the two kinds of rare earth doping electrodes were determined on the basis of its degradation of oil-field wastewater. The optimal preparation processes of the La-doped Ti/TiO2-SnO2 electrodes were 475℃, 90min and 100:10:3, respectively. And that of the Ce-doped Ti/TiO2-SnO2 electrodes were 500℃, 90min and 100:10:5, respectively.The micrograph and structure of the electrode surface and the element composition of surface layer were analyzed by SEM, EDX and XRD. Experimental results showed that doping of rare earth could increase the specific surface area of the coating, and was in favor of grain refining and enhancing the electrical conductivity and electro-catalytic ability of electrodes. Rare earth doping with appropriate amount could promote the replace of Ti in the lattice of TiO2 by Sn. Excessive doping would damage the lattice of TiO2, and decrease the ability of electrode, to the extent that is lower than that of non-doped ones.The degradation processes and mechanism of oil-field wastewater were studied. The result indicated that the best degeneration parameters were obtained when the Ce doped Ti/TiO2-SnO2 electrode was used as anode and the pure Ti board as a negative pole, electrode buried area and interval were 4cm2 and 2cm, the current density was 30mA/cm2, electrolytic concentration of NaCl was 10g·L-1, pH was 3~5, tempreture was 30℃and the electrolysis time was 60min. The average removal rate of oil content and CODcr were 92.8% and 89.2%, respectively. Under the best conditions, contaminant was degradated to other intermediate substances during degradation, finally mineralized to CO2 and H2O.