Study On Degradation Of Simulated Dyeing Wastewater With Advanced Oxidation Processes Intensified By Rotating Packed Bed

The printing and dyeing industry is of importance in China. Inorganic salts are often used as accelerating or retarding agents in the printing and dyeing processes, thus the printing and dyeing wastewater is refractory due to complicated composition and diverse properties. With the progress of fiber industry and dyeing and finishing technologies, the printing and dyeing wastewater treated by conventional methods is unable to meet the requirements of discharge, and new processes have been developed, among which advanced oxidation processes (AOPs) have exhibited strong application potential due to their high efficiency and without secondary pollution.AOPs mainly include O3 process,03/Fenton process, O3/UV process and so on. Ozone AOPs can easily produce the hydroxyl radicals strong oxidizing ability The hydroxyl radicals can the organic compounds in the water and convert them, into non-toxic small molecules, or even completely mineralize them, resulting in efficient and environmentally-friendly treatment of the printing and dyeing wastewater. The key issue of ozone AOPs in application is the gas-liquid mass transfer efficiency of ozone. Therefore, this thesis proposes the combination of the Higee technology with ozone AOPs to promote the absorption efficiency of ozone and the treatment effect of printing and dyeing wastewater by taking advantage of the Higee technology in the intensification of gas-liquid mass transfer.A Higee equipment - Rotating Packed Bed (RPB) was employed to intensify the ozone AOPs of O3 and O3/Fenton for the treatment of the printing and dyeing wastewater of acid yellow 23. The effect of various conditions on the degradation of acid yellow 23 was explored, and suitable operating conditions were determined. The influence of inorganic salts on the treatment of acid yellow 23 by ozone AOPs was investigated. The mechanism of the oxidation of acid yellow 23 by ozone was also studied. The main results are as follows:1. The effect of operating conditions on the treatment of acid yellow 23 wastewater by the O3 and 03/Fenton processes in the RPB was investigated. In the O3 process, the decolorization of the acid yellow 23 and COD removal rate increased first and then remained stable with the increase of the RPB rotating speed, initial pH of wastewater and O3 concentration, but decreased with the increase of liquid flow rate, and remained stable with the increase of the temperature. In the O3/Fenton process, the decolorization of the acid yellow 23 and COD removal rate increased first and dropped then with the increase of Fe2+ concentration, RPB rotating speed and the initial pH of the wastewater, and increased first and then remained stable with the increase of H2O2 and O3 concentration.2. In the O3/Fenton process, the increase of NaCl and KH2PO4 concentration had adverse effect on the decolorization of acid yellow 23, COD removal rate and biodegradability. The decolorization of the acid yellow 23 wastewater and COD removal rate decreased first and then remained stable with the increase of Na2SO4 concentration, and the Na2SO4 concentration had no effect on the biodegradability of the wastewater. The NaNO3 concentration had little effect on the decolorization, COD removal rate and biodegradability of the wastewater. In the O3 process, the addition of inorganic salts had little effect on the treatment of the acid yellow 23 wastewater.3. The acid yellow 23 wastewater after the treatment was analyzed by the ultraviolet-visible spectra to determine whether the azo bond broke, and by liquid chromatography-mass spectrometry to detect the products of the oxidation process. The possible oxidation degradation pathways of acid yellow 23 were deduced according to the products and the oxidation mechanism.