The Study For Photocatalytic Oxidation Of Cyanide Wastes By Nano-TiO₂ Powder

Wastewater of containing cyanide which exists generally with serious harm is an important industrial wastewater for its particular characteristic in the treatment. In this paper, a new process of photocatalytic oxidation of nano-meter TiO2 which uses high efficiency nano-meter TiO2 catalysts and O2 in the air as oxidant is put forward by the source, harm, the present situation of treatment and analysis on usual treatment of wastewater of containing cyanide.This paper reports the nano-meter material, the technology and the future application on industrial pollution treatment. The methods of preparation of nano-meter TiO2 involve physical method (also as machinery crushing method) and chemical method (including CVD, liquid phase method and solid phase method) as well as the mechanism of nano-meter TiO2 photocatalytic oxidation semiconductor and its application in the organic wastewater treatment. The photocatalytic oxidation decomposition of aqueous NaCN solution is taken as reacted model and the factors which influence the degradation efficiency on CN－by nano-meter TiO2 are discussed.The result shows that degradation is in good efficiency when the PH value is 6.5, and HCN escapes more and more as the acidity increases. The good degradation efficiency is not entirely resulted by the photocatalytic oxidation decomposition.The solution is stable and HCN does not escape in alkaline condition.The nano-meter TiO2 showed great degradation rate to CN－ when TiO2 is used in small quantity.The more and more addition of TiO2 results in the improved degradation efficiency on CN－ and system solid particle and optical screening capacity and scattering as well as the decreased effective light that entering the reaction place. The stronger the photocatalytic activity, the better the degradation efficiency on CN－.The degradation efficiency on CN－ tends to be fast at first and then turns slow when the same quantity of catalysts are used.In the same reaction time, degradation efficiency declined as the starting concentration of CN－ increases. On certain condition, the degradation efficiency on CN－ is in direct proportion to the strength and area of illumination , which proves that it is the solution surface on which thereaction occurred.The photocatalytic oxidation of nano-meter TiO2 on CN－ in the actual wastewater has the same result as that of the reacted model .The photocatalytic oxidation of nano-meter TiO2 on CN－ has a reaction order of 0.5 and a reactivity constant k=1.0175×10-2 (mmol/1)1/2.(min)－1.The experimental result is quite the same as that of the analysis and predication of kinetic equation.The study has innovation in the process, the photocatalytic degradation on CN－ by nano-meter TiO2 for which the process of photocatalytic degradation is workable and the basic experiment is valuable has not been reported. The photocatalytic degradation on CN－ by nano-meter TiO2 is in good efficiency in optimization experimental conditions and has potential value in development and application.