Photoelectrocatalytic Degradation Of Organic Dyes By CoFe₂O₄/TiO₂/flake Graphite Three-dimensional Electrodes

The dye wastewater is a kind of organic wastewater which is high chroma, complicated composition and difficult to be degraded. After the dye wastewater discharges to water, it will cause serious harm to the water environment and human health. So high efficient and non-polluting method to deal with such industrial wastewater has already become a researchful focus. The three-dimensional electrode photoelectric catalysis reaction system that combines with three-dimensional electrode and photocatalysis can not only overcome the defects of TiO2 photocatalytic oxidation, and can make up for the inadequacy of two-dimensional electrode electrochemical oxidation. Therefore, it is very important to study the treatment of organic dye wastewater by the three-dimensional electrode photoelectric catalysis reaction system.CoFe2O4/TiO2/flake graphite composites was synthesized by sol-gel method, and and as particle electrodes, applied to the three-dimensional photoelectric catalysis reaction system, in which the xenon lamp, stainless steel sheet, anhydrous Na2SO4, rhodamine B and malachite green was respectively used as light source, cathode and anode, electrolyte and pollutant degradation model.The experiment prepared different CoFe2O4 doping ratio, different calcination temperature and different load times on flake graphite particle electrodes, and studied its photoelectric catalysis performance, so as to obtain the best preparation conditions of the particle electrodes. The results show that:when CoFe2O4 doping ratio was 3%, the calcination temperature was 500?, CoFe2O4/TiO2 load times on the flake graphite was 1 times, the photoelectrocatalytic performance of CoFe2O4/TiO2/flake graphite particle electrodes was the best.The CoFe2O4/TiO2/flake graphite particle electrodes was characterized by BET method, scanning electron microscope(SEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) to analyze its morphology, crystal structure, elements and valence. The results show that the specific area of loaded flake graphite electrode particles was 0.7438m2/g while the specific area of naked flake graphite electrode particles was 5.2446m2/g, and the surface of loaded flake graphite electrode particles had distributed uniformly with a layer of anatase TiO2 and spinel compound semiconductor.Batch experiments were conducted to investigate impacts of electrolyte solution concentration, dosage of particle electrodes, electrolytic voltage, aeration intensity, initial pH and initial concentration on photoelectrocatalytic degradation of rhodamine B and malachite green. And the degradation kinetics under different initial concentration was also studied. As the same time the reaction mechanisms was preliminarily investigated. The experimental results demonstrated that the synergetic enhancement effect was produced in the combined photocatalysis and electrocatalysis process, and when the Na2SO4 concentration was 0.03mol/L, catalyst dosage was 6.67g/L, electrolytic voltage was 8.0V, pH of initial solution was 3, aeration rate was 0 and reaction time was 45 min, the highest removal of 15mg/L Rhodamine B was 97.6%. For 10 mg/L of malachite green solution, when Na2SO4 concentration was 0.01mol/L, catalyst dosage was 6.67g/L, electrolytic voltage was 14.0V, pH of initial solution was 2.5 and aeration rate was 0, the removal of malachite green could reach 96.87% after 45 minute. The pseudo-first order model could correlate well with the results of photoelectrocatalysis degradation process of Rhodamine B and Malachite green, and·OH was a kind of important active substances in photoelectric catalytic reaction process.