Restaurant wastewater treatment by electrochemical oxidation in continuous process

Abstract

The specific electrode is necessary for destruction of organic pollutant in restaurant wastewater by electrochemical oxidation. In this research, the specific electrode was prepared by metal-organic chemical vapor deposition (MOCVD) in a hot- all CVD reactor with the presence of O2 under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO2 active layer. The optimum condition for Ir film deposition was 300 oC, 125 of O2/ MeCp)Ir(COD) molar ratio and 12 torr of total pressure. While that of SnO2 active layer was 380 oC, 1200 of O2/TET molar ratio and 15 torr of total pressure. The simulation of Ir deposition using FLUENT® shows the good agreement with the experimental data. However, the case of 300 oC and titanium substrate, the simulation results have deviated from the experimental data that maybe attributed by the different on surface chemistry of each substrate or the higher surface roughness of titanium substrate. The prepared SnO2/ r/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three- lectrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed in 2 hr. In first 2 hr, the kinetic investigation gives a zero-order respect to TOC of model solution and the destruction of pollutant was limited by the reaction kinetic. Then, it was first-order respect to TOC of model solution that limited by the mass transfer of pollutant to the electrode. Furthermore, the SnO2/Ir/Ti electrodes were used in this restaurant wastewater treatment within Chulalongkorn University. The increase of current density leads to the decrease of TOC and COD removal efficiency as a results of the increases of cell voltage and side reaction. Increasing residence time from 2 to 3 hr had not greatly influenced on TOC and COD removal efficiency due to slower reaction after 2 hr. The SnO2 film thickness had no effect on TOC and COD removal efficiency because the production of adsorbed hydroxyl radicals for pollutant destruction occurred only at the surface of electrode