A Nano-TiO₂-KMnO₄ Photocatalytic Oxidation System For Determination Of Chemical Oxygen Demand And A Study On Biodegradation Of Methyl Orange

The application of photocatalytic oxidation for determination of chemical oxygen demand and a study on aerobic biodegradation of azo dye methyl orange were carried out in this paper.Chemical oxygen demand is an important parameter for water quality, because it can assess the concentration of organic contaminants in water resources. And the conventional COD evaluation method (dichromate method) has several drawbacks, such as long analysis time, complex operation procedures, and highly toxic (Hg(II) and Cr(VI)) reagents. Therefore, attempts have been made to develop new methods. A nano-TiO2-KMnO4 photocatalytic oxidation system combined with spectrophotometry for rapid determination of chemical oxygen demand (COD) was proposed in this paper. It is found that the method has merits of wide linear range and strong tolerance to the interference of chloride. Under optimized conditions, this method can respond linearly to COD of potassium hydrogen phthalate in the range of 0.1 ~ 320 mg/L. And the tolerable concentration of chloride ions is over 1500 mg L?1 for an interference of less than 5%. When the surface of nano-TiO2 has been fluorinated, it can enhance the rate of photocatalytic oxidation of organic matter and the rate of coupled photocatalytic reduction of MnO4-. This method was satisfactorily applied to determine the COD values in mildly contaminated samples such as tap water, Yangzi River water and lake water.Azo dye wastewater is difficult to dispose, yet with large drainage volume, so effective disposing becomes more and more emergent while the environment protection draws more and more attention. Because the biochemical degradation can degrade azo dye more efficiently and with less possibility of re-polluting, therefore it will be the beacon for developing of dye wastewater disposing technique. In this paper, a strain of aerobic microorganisms selected by our laboratory is used as microorganisms,and the bulk culture conditions for the biodegradation of azo dye methyl orange by this mixed bacteria were investigated. It found that the microorganisms can keep the higher growth rate and the activeness under the circumstance of the temperature from 30℃to 40℃and pH=6~8. When the initial concentration of methyl orange is 50mg/L, both the decoloration and degradation is as high as 97%. When dye's concentration increased, the rate of decoloration and degradation dye is decreased.