Degradation Of High Concentration Reactive Azo Dyes By O₃ Coupled Microwave Induced Fenton-like Technology

As the maximum amount of dye wastewater,azo dye wastewater has been the focus for researchers currently.Among them,reactive azo dyes are widely used because of its stability and low cost.In recent years,advanced oxidation technology(AOPs)as a chemical method have achieved good results in the degradation of dye wastewater,but more and more research tend to use two coupled advanced oxidation techniques so as to remove the contaminants efficiently.In this paper,the novel microwave complicate catalyst—copper ferrite supported on granular activated carbon is prepared,then ozone oxidation technology combined with microwave-induced Fenton-like technology is used to treat simulated azo dye wastewater and large amount of actual reactive azo dye wastewater with high concentration.We discuss the synergistic effect between the two advanced oxidation technologies,investigate the related factors,explore the catalyst stability and the feasibility of the hyphenated techniques.The specific contents are as follows:(1)We successfully prepare the novel microwave catalyst——CuFe2O4/GAC by sol-gel method.The characteristic diffraction peaks for CuFe2O4(JPCDS no.25-0283)at 20=18.50,30.16,35.64,57.05 and 62.77 appeared.According to the Scherer equation,the grain size of CuFe2O4 in the complicate catalyst is about 9 nm.It can be seen by SEM that when supported on GAC,copper ferrite wrapped on the surface of activated carbon finely.Moreover,the isoelectric point(pHIEP)of CuFe2O4/GAC is around 7.8,which is weak alkane and easy to contact with reactive azo dye.The analysis of FTIR spectra shows that the absorption peaks of catalyst at 570 and 546 cm-1 are observed,which are ascribed to tetrahedral and eight octahedral stretching vibration of copper ferrite.In addition,it is observed from XPS analysis of CuFe2O4/GAC that four intensive peaks appeared at binding energies of 284.6,530.2,711.7 and 934 eV,which were ascribed to C 1 s,O 1 s,Fe 2p,and Cu 2p.All results from XRD?SEM?FTIR and XPS show that CuFe2O4 was supported well on the surface of GAC,the supported catalyst——CuFe2O4/GAC was successfully prepared?(2)A set of continuous ozone-microwave-ultrasonic device for wastewater treatment is designed in this experiment.First,the wastewater is aerated in ozone for certain time,and then it is transited into microwave Fenton-like reactor to be degraded.Last,ultrasonic ractor is utilized to clean the reactor.Once using this device to degrade wastewater,we can realize that the multitudinous wastewater can be treated and it can reduce the cost of wastewater treatment,making the whole system high efficiency and energy conservation.(3)After 60 min O3 aeration and 5 min microwave-induced Fenton-like reaction,the decolorization rate of 8 L reactive brown dye effluent with 500 mg/L reach 60%,BOD5/COD value(B/C)is more than 0.3 and the toxicity of the wastewater is greatly reduced.The influence factors were investigated and optimized,the optimum reaction conditions are as follows:catalyst dosage of 5 g/L,microwave power of 2 kw and H2O2 concentration of 1 mL/L.In addition,it exhibited a broad pH range in microwave-induced Fenton-like reaction.After the tenth run,the decolorization rate of reactive brown dye effluent can still reach 50%and B/C value is 0.265,which is beneficial for subsequent biochemical treatment.In addition,actual high-concentration reactive azo dye effluent taken from Jiangsu Chemical Co.,Ltd was treated by the O3-microwave-induced Fenton-like device.The result shows that COD value of the effluent decreased from 2680 mg/L to 1660 mg/L and the BOD5/COD value(B/C)was up to 0.27,indicating the biodegradability was improved greatly.(4)To explore the mechanism of the reaction process,tertiary butanol,sodium oxalate and benzoquinone as ·OH scavenger,h+ scavenger and O2·-scavenger were added into the solutions,respectively.The results display that when added tertiary butanol and benzoquinone during the degradation,the degradation process was obviously restrained.However,inhibition is not obvious when add sodium oxalate,indicating that the main active species in degradation of reactive brown dye in O3-microwave-induced Fenton-like system are ·OH and O2·-.Their production is accelerated to enhace the removal of pollutants under microwave radiation,improving the degradation efficiency greatly.(5)The commercial cost of treatment for high-concentration reactive azo dyes wastewater is 50 yuan per ton,while the cost of this technology for azo dye effluent treatment is just 30 yuan per ton,which is 40%below the commercial price.In the future application,it can bring great economic benefits for enterprises.