Study On Catalytic Degradation Performance Of Tungsten Heteropolyacid Salts On Dye Wastewater

Dye wastewater is one kind of organic industrial wastewater that is hard to be degraded in recent years. It always contains a great amount of organic dye molecules, which are heavy chroma, low penetrability and difficult to be biochemical degraded, and has a serious impact on the survival of aquatic life. In addition, dye wastewater will endanger human health and ecological environment. Therefore, effective methods are urgently needed to treat this type of wastewater.Three Keggin type heteropolyacid salts, Nas(6)[XZrW11O39]·nH2O (X= Fe and Ni, the following abbreviated as XZrW) and Na13[Ce(ZrW11O39)2]·nH2O (the following abbreviated as CeZrW) were synthesized via a classic acidification method. The thermal stability of synthesized heteropolyacid salts was investigated by thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), simultaneously, the number of crystallization water molecules of heteropolyacid salts was calculated. The experimental results indicate that, the synthesized three tungsten heteropolyacid salts (Fe, Ni and Ce) are well equipped with good thermal stability, and the corresponding number of crystallization water molecules was 23,20 and 55 respectively. The structure and other properties of these heteropoly compounds was characterized by fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction powder pattern(XRD) and ultraviolet (UV) spectroscopy. In view of the results of the characterization, three heteropoly compounds are demonstrated to be typical Keggin structure of heteropolyacid salts.Acidic blackish green is one of the typical pollutants of dye wastewater, owing to the benzene, naphthalene rings, azo and other functional groups in the structure of acidic blackish green are belongs to refractory functional groups. In the experiment, acidic blackish green was applied to prepared simulated dye wastewater, and rendered synthesized heteropolyacid salts as the catalysts, the catalytic oxidation degradation performance of heteropolyacid salts on acidic blackish green with ultrasonic wave was validated. The results of the experiment show that:1) The catalytic property of NiZrW is optimal in the synthesized three heteropolyacid salts, and its degradation rate is up to 95.65%, conversely, the catalytic property of FeZrW is the weakest; 2) Under the experimental condition, the degradation rate of adding FeZrW heteropolyacid salt to dye wastewater is not even as good as blank experiment; 3) Some experimental factors such as the dosage of heteropolyacid salts, the pH value and initial concentration of dye wastewater, the ultrasonic frequency and power, all of which have certain effects on degradation rate; 4) At the same time, the reaction kinetics of heteropolyacid salts degrading different concentration of dye wastewater with ultrasonic wave were studied, the results indicate that the linear coefficients (R2) of the fitting curves are more than 0.96, which means the process of tungsten heteropolyacid salts catalytic degrade acidic blackish green dye wastewater with ultrasonic wave is basically in accordance with the pseudo- first order kinetic model.