Research On Degradation Processes Of Three Typical Dyes By Advanced Oxidation Technology

The rapid development of textile industry leads to the increasing of discharge of wastewater from printing and dyeing companies,posing a great threat to ecological balance and human health.This study selected the typical Alizarin Yellow R(AYR)of azo dye,Alizarin Red(AR)of anthraquinone dye and Methyl Blue(MB)of triphenylmethane dye as the target pollutants,configuring simulated printing and dyeing wastewater,using H2O2 oxidation(HO),Electro-Catalytic Oxidation(EC)and corona discharge plasma(CD)technologies to treat them.The analysis of the feasibility and degradation effect of each dye with different treatment methods were studied,and the analysis of the variety of the fluorescence and the position of the interruption bond in the molecular structure of the dyes by different treatment methods were studied respectively.The results of degradation effect of three dyes by H2O2 oxidation technology showed that this technology is not feasible for the decolorization of Alizarin Yellow R and Alizarin Red solution,but the Methyl Blue is higher.The effects of the initial concentration of MB solution,the volume fraction of H2O2 and the initial pH value of the solution on the color removal rate were studied.The results showed that the decolorization rate can reach 97%after 12 h of mass concentration of Methyl Blue is 1000 mg/L with the volume fraction of H2O2 is 5%.The UV-Vis spectrum result showed that the absorption peaks of the original Methyl Blue gradually decrease with the prolongation of the reaction time and then disappear,and the new absorption peaks are produced at 272 nm and 374 nm,indicating that the H2O2 oxidation technology can effectively destroyed the structure of Methyl Blue.The new absorption peaks of 272 nm and 374 nm are due to the absorption of intermediate products produced in the degradation process.After the H2O2 oxidation of 24 h,compared the infrared spectra and the fitting curves of infrared spectra(1750 cm-1?1540 cm-1)of the methyl blue solution before and after H2O2 oxidation,the absorption peak situates at 1676.9 cm-1 of C=N outside the ring in the chemical structure of methyl blue disappears,and the adsorption peak of N=O is produced in 1386.4 cm-1,indicating that the C=N has been destoryed in H2O2 oxidation process,and the intermediate structure containing N=O.The Electro-Catalytic oxidation technology was used to degrade Alizarin Yellow R,Alizarin Red and Methyl Blue solution.The IrRuTi electrode was used as anode while the Titanic mesh as cathode.The effects of supporting electrolyte types(Na2SO4 and NaCl),initial dye concentration(500 mg/L,1000 mg/L and 1500 mg/L),initial pH values(3,5,7,9 and 11).electrolytic voltage(6 V,8 V,10 V and 12 V)and the concentration of NaCl(2 g/L,4 g/L,and 6 g/L)on the color removal rate of each dye,obtaining the optimal parameters of the decolorizing rate from the dye in the electrocatalytic process.The changes of pH value and TOC content of the dye solutions during the degradation process were measured,and the spectral behavior of each dye degradation process was confirmed by spectroscopy.The experimental results show that the pH value of the solution is gradually smaller during the degradation process,and the total organic carbon content decreases with electrolysis time increasing under the optimal degradation conditions,indicating that some of the dye molecules have been mineralized to produce CO2.In addition,the intensity of the absorption peaks in the UV-Vis gradually decreased with the electrolysis time and then disappeared,indicating that the concentration of target pollutants in the solution gradually decreases.The variety,intensity and position of the fluorescence substance in the three dimensional fluorescence spectra also changed to a certain extent,indicating that the technology can effectively degrade or transform some fluorescent substances.Compared the infrared spectra of each dye before and after degradation,the peaks position took place such as red-shifted,blue-shifted,the disappearance of the original peaks and the generation of the new peaks,which further indicated that this technology can effectively destroy the molecular structure of the dyes.Corona discharge plasma technology was used to treat this three kinds of dyes.The effect of the discharge time,initial concentration of dyes(500 mg/L,1000 mg/L and 1500 mg/L),initial pH value(3,5,7,9 and 11)on the degradation rate of three dyes were studied.The pH value,TOC and TN content of each solution during the degradation process were measured with the discharge time increasing.UV-Vis spectra,three-dimensional fluorescence spectra and infrared spectra were used to study the spectral behavior of each dye in the degradation process.The results showed that the pH value of the solution during corona discharge plasma degradation first increased and then decreased,and the TN content in the solution gradually increased with the prolongation of discharge time in the whole discharge process.The content of TOC,color and the peaks in their UV-Vis spectra all gradually reduced with the reaction time in the AYR and AR solutions.But for the MB,the TOC content and color of the solution all get the maxium value at discharge time of 5 min,and then gradually decrease with the increase of the discharge time.The intensity of the adsorption peak of the chromophoric group of the MB solution in the UV-Vis spectrum was also the maximum at the discharge time of 5 minutes,and then decreased gradually.The 3-D fluorescence spectra showed that the type,intensity,and position of the fluorescent substance in the solution all changed with the discharge time increasing,which indicated that this technology can effectively degrade or transform the fluorescent substance in the solution.Compared the infrared spectra of each dye before and after degradation,the peaks position took place such as red-shifted,blue-shifted,the disappearance of the original peaks and the generation of the new peaks.which further indicated that this technology can effectively destroy the molecular structure of this three kinds of dyes.For the desizing wastewater,bleaching wastewater and real textile wastewater from printing and dyeing enterprise,corona discharge plasma technology was used to treat these wastewater,and degradation effect were also studied.The experimental results showed that the TOC removal rates of desizing,bleaching and real textile wastewater reach 4.1%2.8%and 5.3%respectively,after 30 min discharge.Meanwhile,the BOD5/COD values of each wastewater increased from 0.23,0.07,and 0.11 to 0.31,0.19,and 0.35,respectively,indicating that the biodegradability was greatly improved.Therefore,considering this technology as a pre?treatment method for the degradation of printing and dyeing wastewater,providing a feasible pretreatment process for further combination with biological degradation.Combined with the above studies,the experimental results in this paper have important theoretical guidance and practical application for the treatment of Alizarin Yellow R,Alizarin Red and Methyl Blue solution using H2O2 oxidation,electro-catalytic oxidation and corona discharge plasma technology.Corona discharge plasma technology can improve the biodegradability of real printing and dyeing wastewater,which provides practical application for this technology used in the biochemical pretreatment of printing and dyeing wastewater.