Studies On Photo-electro-chemical Catalytic Decolorizing Degradation Of Dye Wastewater

A new two-compartment photo-electro-chemical catalytic reactor was designed, in which thermally formed TiO₂/Ti was used as anodes, graphite as cathode and a saturated calomel electrode as the reference electrode. In this reactor, dye wastewater was degraded with TiO₂/Ti electrode in anodic compartment; simultaneously, hydrogen peroxide produced by graphite electrode reducing dissolved oxygen and UV structured the H₂O₂/UV system, and dye wastewater was also degraded in cathodic compartment.H₂O₂ is the crucial element of the H₂O₂/UV system. The favorable condition of obtaining H₂O₂ was investigated before treating dye wastewater firstly. The initial pH of solution, cathodic potential, reactive time, aeration, stirring, the concentration of electrolyte, cell voltage and so on factors which affect H₂O₂ output were studied.Based on above experiments the treating of reactive red X-3B was performed. Firstly, the effect of photolysis, electrolysis, photocatalysis and photoelectrocatalysis on the reactive red X-3B were compared.The results showed that the decolorizing rate of photoelectrooxidation was higher than those of direct photolysis and electrolysis in cathodic compartment; the synergetic effect of the photoelectrocatalysis was obtained in anodic compartment.Then, the influence of the initial pH of solution, cathodic potential, reactive time and the initial concentration of solution on the reactive red X-3B oxidation were analyzed in photo-electro-chemical catalytic system. Results showed that the decolorizing rate of the reactive brilliant red X-3B solution got down to the lowest in neutral pH solution and increased at both acid and basic pH range, and the optimum pH was 3.0; the decolorizing rates didn't always increase with the decreasing of the cathodic potential(E_c), the optimum E_c was-0.6V; the decolorizing rates decreased with the increasing of the initial concentration of solution. Under the conditions of the supporting electrolyte concentration was 0.02mol·L^-1, initial solution pH=3.0 in cathodic compartment and pH=6.5 in anodic compartment, cathodic potential E_c=-0.6V, the reaction time was 80min, the highest decolorizing rate of 99.3% was obtained in cathodic compartment, and 88.7% in anodic compartment when the initial concentration of reactive red X-3B dye was 30mg·L^-1.Compared with the"two electrodes and single effect"reactor only having photoelectrocatalysis with TiO₂/Ti anodic electrode, the new reactor has obviously enhanced the degradation of the reactive red X-3B and achieved the purpose of"two electrodes and double effects". In the end, in order to study feasibility of the reactor, the experiments had chosen some dyes such as acid scarlet 3R,direct fast black and fuchsin basic to degrade. The results showed that the new type of reactor had preferable catalytic degradation effects on these dyes.