Study Of Photoelectrocatalytic Degradation Of Organic Dyes By Pr-Co/TiO₂/Flake Graphite Particle Electrode

The dye wastewa ter has the characte ristics of high quantit y, high colortiy, complex composition, hard biodegr adable and harm to the environment. So, the treatment of dye wastewater is one of the hot test spots of environmental treatment. Photoelec trocatalysis is a state-of-the-art technology for waste water treatment based on photocatalytic and electrocatalytic oxidation. It has a important significance in the environment improvement with the advantages of efficient, energy conservation and environment friendly. Therefore, this paper adopts three-dimensional particle electrode photoelectric catalytic of organic dyes.With the purpose of improving the photocatalytic property of TiO₂, we have chosen Pr and Co co-doping to modify it in this paper. Pr-Co/TiO₂ /flake gr aphite was first synthesized by so-gel method and used it as particle electrode. In the study, 500 W Xenon lamp used as a light source, D.C power supply provides the bias voltage. Two slices of equal area of stainless steel plate were used as anode and cathode of three-dimensional electrode respectively.The doping amount of Pr and Co were optimized: under the condition of n（Ti）: n（Pr）: n（Co）=1:0.003:0.001, the P r-Co/TiO₂ /flake graphite particle electrode showed the optimal photoelectrocatalytic performance, synergic effect and good stability. The Pr-Co/TiO₂/flake graphite particle electrode was characterized by BET, SEM, XPS and FTIR.The effects of six operating parameters such as electrolyte concentration, applied voltage, the dosage of particle electrode, aeration rate, initial pH and concentraion of RhB on the degration efficiency of RhB were investigated in the study. The results showed that under the conditions of electrolyte concentration for 0.03mol/L, applied voltage for 10 V, dosage of particle electrode for 6.67g/L, aeration rate for 30 m L/min, initial pH for 3 and the initial concentration of RhB for 25mg/L, the removal rate of RhB reached 98.6% in 45 minutes. The kinetics of photoelectrocatalytic degradation of RhB was found to follow the first-order rate law in a certain range of time and concentration.To study the particle electrode for other organic dye wastewater is also has better degradation effect,used it for photoelectric catalytic degradation of acid fuchsine. Experimental results showed that under the conditions of electrolyte concentration for 0.02mol/L, applied voltage for 6V, dosage of particle electrode for 6.67g/L, initial pH for 2 and the initial concentration of acid fuchsine for 20mg/L, the removal rate of acid fuchsine reached 97.5% in 45 minutes. When the concentration of acid fuchsin was 50mg/L, the removal rate of acid fuchsine still amounted to 96. 5% in 60 mins. The kinetics of photoelectrocatalytic degradation of acid fuchsine was found to follow the first-order rate law in a certain range of time and concentration.The photoelectrocatalytic degradation mechanisms of RhB and acid fuchsine were discussed in the end. Tert-butyl alcohol was used to capture the hydroxyl radicals in the systems of photoelectrocatalytic degradation of RhB and acid fuchsine. The photoelectrocatalytic degradation intermediates of acid fuchine have been identified by LC-MS.