| Organic dyes are the largest group of pollutants in wastewater produced from textile and other industrial process. The conventional methods used for textile wastewaterpurification are biologic oxidation and physical-chemical treatment (e.g., coagulation-flocculation, activated carbon adsorption). These processes are not sufficiently efficient since dyes are hardly removable due to their large molecular weight and high water solution. Moreover after their treatment sophisticated subsequent processes are still needed. Therefore, attention has been paid on exploring non-conventional technique to degrade dye wastewater by scholars in this field. A new method for dye wastewater degradation was studied in the current dissertation. For convenient, dye red 3B solution was taken as representative of dye wastewater. Varied degradation methods were studied in self-made US/TiO2 apparatus , UV/US/TiO2 apparatus , magnetizing associated US/TiO2 apparatus with TiO2 as catalyst. The main results were as follows:The TiO2 catalyst was prepared and used for photocatalytic degradation with sol-gel method, the particle were characterized by X-ray diffraction (XRD). Effects of dye red B initial concentration, catalyst quantity, inorganic salts, aeration amount, pH value were discussed in detail and the reaction was described by Langmuir-Hinshelwood (L-H) equation. The results showed that increasing the initial concentration of dye red 3B, the rate constants changed from fist-order reaction model to zero-order reaction. The apparent rate constant linearly increased with increasing the TiO2 amount in the range of 2.5g/L. Both anions (Cl-, SO42-) and cations (Na+, K+, Ca2+, Mg2+) retart the rate though and the former is the major factor. Aeration quantity made the adsorption rate constant changed thus affect the kinetic behavior. The efficiency of decolorization in acid is better than in alkali and the reaction has an optimum pH value (pH=3). While pH keeps increasing, adsorption of dye red B reduced. Optimal reaction temperature is during 50-60 C.The photocatalytic degradation of dye red 3B by variant particle size of TiO2 combined with ultrasound. The use of ultrasound had a pronounced effect on the rate and efficiency of dye red 3B destructions as compared with UV-light degradation. The combination of action of ultrasonic wave and UV assisted photocatalysis yielded synergistic effect for the catalysts with the smaller particle size (TiO2-A, with average size of 110nm), degradation efficiency increased 43.57% compared with UV-light photocatalytic degradation alone, while no enhancement was observed for the smallest particle size photocatalysis (TiO2-E, with average size of 11nm). Catalyst quantity of the optimal synergistic effect was 0-0.3g/L.The possible reason of increased activity under ultrasonication were proposed: aggregate breakage and scavenging increase the mass transfer and activity catalyst in addition to free radical formation produced by ultrasound. The results of factor test showed that the maximum concentration site of catalyst is 0.3g/L; increasing the initial concentration of dyered 3B, the rate and zero-order rate constants increased; a certain mount of NaCl promote the degradation efficiency; the rate of decolorization in aeration is better than in non-aeration; the efficiency of the degradation depends on light intensity and ultrasonic time in some degree.The photocatalytic degradation of dye red 3B using suspended TiO2 combined with magnetization was studied in this paper. Compared with the unmagnetized sample, the strength of UV absorption of magnetized sample increased. The magnetic field affects the process of photocatalytic reaction. Through a series of experiments that were carefully designed, the different magnetization time and magnetic field strength made photocatalytic reaction change in varying degrees. This research will play important role for the study of possible mechanism of magnetic field effect on photocatalytic reaction.
|
PDF Full Text Request