Study On Preparation Of Electro-catalytic Electrode Materials And Application To Wastewater Treatment

The electrochemical technology has attracted a great deal of attention recently, mainly because of its special advantage. The electrodes which are the heart in electrochemical reaction system are the important effect on increasing the removal rate of pollutions and reducing energy consumption. So the study of making electrodes with high electrocatalic ability has great practical significance.PbO₂/Ti and gas diffusion electrode are perspective materials due to their excellent electrochemical performances. Potential application such as wastewater treatment, electroanalysis, have been proposed and are being actively pursued now. The preparation of the novel Fe-doped PbO₂/Ti, three gas diffusion electrodes and their applications to wastewater treatment had been investigated.Fe doped PbO₂/Ti electrode was produced by electro-deposition and the electrode was studied by SEM, EDX, XRD. The characteristics of degradating organic pollutants were studied by electro-catalytic oxidation of Fe-PbO₂ /Ti, taking paranitrophenol and sodium dodecyl benzene sulfonate as model pollutants. The results show that the degradation efficiencies of paranitrophenol was bigger than sodium dodecyl benzene sulfonate's. Various influence factors such as the initial concentration, current density and pH were examined. Furthermore, the degradation kinetic models were discussed. The results show that the first order reaction model can be used for the fitness of the organic pollutants removal.The electrochemical oxidation mechanism and degradation process of paranitrophenol on Fe-PbO₂/Ti electrode were studied in detail adopting the techniques of cyclic voltammetry, AC Impedance, combined with efficient liquid chromatographic technique and GC/MS. It was found that·OH was very important for degradating organic pollutant and electro-catalytic reaction of organic pollutant was electrochemical burning process. Above the oxygen evolution potential of Fe-PbO₂/Ti anode, the ways of paranitrophenol electrochemical oxidation included indirect electrochemical oxidation and direct electrochemical oxidation together. The results show that the novel Fe-PbO₂/Ti anode had perfect electro-catalytic activity and stability, and the electro-catalytic degraded rateconstant of p-NP increased 24%.The synergetic degradation of paranitrophenol in water by anodic/cathodic electro-catalysis was studied in a new electrocatalytic reaction system using gas diffusion electrode as cathode and Fe-PbO₂/Ti as anode. The influences of initial paranitrophenol concentration, current density, pH and aeration rate on the removal efficiency were investigateded. The degradation kinetics was discussed. The results show that when current density was 24mA/cm², aeration rate was 20mL/s, the removed rate of paranitrophenol with 100 mg/L concentration reached 100% after electrolesis of 55 min, and the cell voltage could decrease 0.5V. This system had low energy consumption, high efficiency and large application range for pH . This novel system had a great application priority.A system to produce H₂O₂ was built with graphite as anode and a gas diffusion electrode made in carbon nanotubes as cathode. The regression analysis was employed to set up a model for H₂O₂ production by the central composite designed experiment. When current density was 10mA/cm², 1.3 L/ min of air flow , the concentration of H₂O₂ could reach 707 mg/ L after an hour.A novel electro-catalysis and electro-Fenton electrochemical reaction system using carbon nanotubes gas diffusion electrode as cathode and Fe-PbO₂/Ti, Fe as double anodes was studied. This system had high efficiency and great potential for future environmental application.Two direct-air cathode single-chamber microbial fuel cells were constructed by using air electrode as cathode, foamed metal as anode and glucose as the anode fed. ACMFC2 had low internal resistance, high power density and nice discharge /charge ability. The internal resistance of ACMFC2 was 3.89Ω, the maximum power density could reach 774.8mW/m². The discharge curve and CV tests revealed that the first discharge capacity and energy was 308mAh/gCOD and 149mWh/gCOD. The ohmic resistance of ACMFC2 was 0.95Ω. When the ACMFC2 was in the activation overpotential area and the ohmic overpotential area, non-ohmic resistance accounted for 92.6% and 75.58% in the internal resistance. A new two-chamber microbial fuel cell was constructed by using potassium permanganate as cathodic electron acceptors.The influences of permanganate concentration and pH on the power generation performances of MFC were researched. The results show that the maximum open circuit voltage could reach 1.68V when permanganate concentration was 500mg/L and pH=2.0. Meanwhile, COD removal efficiency and coulombic efficiency were 87.1% and 45.2%. pH of catholyte was found to affect performance of MFC, which was meliorated when the catholyte is acidity.