In-situ Photoelectroncatalytic Degradation Of Reactive Dyes With Modified Nano-tio₂

Recently, because nano-TiO₂ materials are of such good performance as chemical stability, high photo-catalysis, low cost, no poison and so on. They have been applied to organic compound decomposition, wastewater treatment and air purification, dyeing water decoloration broadly. TiO₂ has become a research hotspot. But how to develop its function effectively has also been a key step to ensure photo-catalysis in good progress and to promote for industries. Take dyeing wastewater treatment for example, TiO₂ has weak adsorption capability for organic compound by itself. If we introduce adsorptive carriers on which TiO₂ are loaded, photo-catalytic efficiency will increase obviously. It is adsorptive carrier's maximum advantage that they can adsorb organic compound around TiO₂ particle, improve local concentration and avoid middle materials volatile or escape. Such behavior can accelerate the reaction. At presence, relative researches have made some progress.The paper adopted Sol-Gel method to prepare nano-TiO₂ and nano-TiO₂ doped La³⁺ of great photo-catalytic property, then continued to utilize ultrasonic dipping-drying-calcining several times to load TiO₂ on activated carbon, formed photo-catalytic agent AC/ TiO₂ with La³⁺. physiochemical properties, morphology and crystalline phase were determined by methods of TG,TEM,SEM,XRD,FT-IR,UV-Vis. Then a novel heterogeneous three-dimensional photoelectrocatalytic reactor, in which isolated multilayer fixed-bed filled with photo-catalytic agent AC/ TiO₂ with La³⁺ as a three electrode of reactor, was designed and characterized by three-dimensional granule electrode and removal efficiency of red reactive dye. Moreover, the paper had studied on red reactive dye removal efficiency for the three processes, including direct electro oxidation, photo-catalysis and photoelectrocatalysis, and completed the La³⁺ doping, supported catalyst, Dye initial concentration, inorganic compound, pH and the applied voltage value on the rate of degradation of the conditions for optimization. The water containing these reactive dyes was decolorized and used for dyeing of cotton fabrics with reactive dyes again. A comparison between color characteristics of dyed cotton fabrics had been done respectively in fresh tap water and the recycled water.It was founded that some anatase TiO₂ with high photo-catalysis had been obtained after heating gel up to 450℃.The effect of dye concentration on photo-catalytic reaction rate followed Langmuir-Hinshelwood kinetic model. By comparison of the reactive dye removal kinetics for the three processes, an apparent photoelectrochemical synergic effect in degradation efficiency was observed in the new reactor for treatment of wastewater containing red reactive dyes. In this three-dimensional photoelectrocatalytic reactor, the sparged air not only could efficiently enhance the mass transfer and the collision of photo-excited TiO₂ particles loaded on reactive carbon, but also could make electric field facilitate to capture the photo-generated electrons.Applied voltage was effectively separated hole and photonics. La³⁺ could reduce crystal size of TiO₂ evidently and improve photocatalysis of AC/TiO₂. And the results indicated that the rate of decoloration of reactive dyeing wastewater had good result with moderate reactive carbon dosage and the pH value for neutral solutions; NaCl improved decoloration of reactive dyeing wastewater. It was found that in general decolorized reactive dyeing wastewater might be available in the dyeing of cotton fabrics with reactive dyes, and Color and fastness could be satisfied.