Ultrasound Combined Ozone Process For The Treatment Of Typical Aromatic Dyes And The Mechanism

The dye wastewater is a kind of high COD,high chroma,and organic wastewater with high biological toxicity.It is difficult to treat and disposal with three aspects problem: 1)color removal,2)biological detoxification and 3)the mineralization of refractory material.One side,ozone could utilize the ozone direct oxidation and the hydroxyl radicals,which were generated by the ozone cracking,indirect oxidation to oxidize the pollutants;on the other hand,ultrasound could promote the mass transfer of ozone in water by cavitation and physical effect,improving the utilization rate of ozone.Ozone can selectively oxidize the dye chromophore,solving the problem of decolorization;free radicals and ultrasonic radiation could destroy the conjugate structure of dyes indiscriminately.Therefore,ultrasound combined ozone process(USOP)for dye wastewater treatment is an ideal and alternative pre-treatment technology.According to the existing problem of high chroma,poor biodegradability of the dye wastewater treatment,the pre-treatment technology is urgent called to make the wastewater decolorize efficient and improve the B/C ratio.This study designed the “USOP-sieve plate tower” system.This system could further improve the ozone utilization rate,the biodegradability of representative dye effluent,and reduce the toxicity of dye effluent of luminescent bacteria inhibition(from moderate toxicity to non-toxic,reducing the effluents environmental risks).The B/C of MG,AR27,AR18 and ARS improved from 0.08,0.08,0 and 0.11 to 0.29,0.25,0.51 and 0.31,respectively.After treated by USOP system,the emission of MG,AR 27 and AR18 dye wastewater discolored completely in very short time period(10min,8min and 8min).According to the lack of systematic study between dye wastewater treatment technology and the dye structure,this thesis chose the three kinds of dyes(azo dyes,anthraquinone dyes,and three phenyl methane dyes): AR27 and AR18,alizarin red AR and alizarin red ARS,malachite green MG,as the research typical aromatic dyes.In addition,this research studied the similarities and differences in the USOP system of decolorization and degradation degree of these typical dyes,and revealed the causes of the differences from the main structure of dye and substituents.By using the quantum chemistry calculation software Gaussian 09,the stabilities of dye molecules were got;the positions of the active sites(atoms)of the dyes molecules,AR 27,the positon of atoms-C18,-C26,-N16=N17-,which reacted with hydroxyl radical more easily than the AR18,and the theoretical criterion of the energy of activation reaction(Ea)were also obtained.The atoms of AR which easily react with the ·OH were C9,C11,C14 and H25.And the active energyies were 30.80?10.74?123.93 and 0.44kcal·mol-1,respectively.The abstraction reaction that ·OH and AR-H25 could happen easily,because it was a reaction without energy barrier.By these means,it was explained that why the different structure types of dyes(azo,anthraquinone and three phenyl methane),isomeric dyes(amaranth and carmine),in the same USOP-sieve plate tower system,the decolorization rate and degradation degree were different.In addition,the molecular stabilities and the activation energies of the elementary reaction determined the degree of difficulty of the dyes degradation reaction,in theory.According to the existing problem of the treatment process of dye degradation pathway was not clear,this thesis proposed quantum chemical simulation(Gaussian 09)and high performance liquid chromatography-mass spectrometry(HPLC-MS)method.This method not only could predict and reveal the degradation pathways of representative aromatic dyes in the USOP system,but also could do a favor to control the environmental risk of the actual processing of dye reaction conditions and provide a theoretical basis.