Study On Biochemical Mechanism Of Decolorization Of Azo Dye Wastewater By Klebsiella Sp

Azo dye is a kind of organic compound which contains azo bond and aromatic group,it is typical dye which used in textile,printing and dyeing industry;The color of the wastewater is determined by the azo bond.In the process of printing and dyeing,the dye wastewater which is not fully produced can cause great harm to animals,plants and human beings.Treatment methods of Azo dye wastewater are currently focused on advanced oxidation,biological,adsorption treatments,etc.Advanced oxidation process is mainly focused on the study of ·OH,·SO₄^2-catalysts,Biological methods are mainly concentrated in the sludge method,the new type of bacterial fermentation,etc.The adsorption method is mainly focused on the improvement of new carbon materials and the addition of catalysts.Compared with the adsorption process and advanced oxidation process,the treatment capacity of biological treatments is limited,the energy consumption is high,and the biological method is thoroughly purified,the energy consumption is low,and the pollution is little;It has been become a hot spot in the research of azo dye wastewater.Among them,the microbial treatment method based on the addition of extracellular electron shuttle has been paid more and more attention because of its economy and high efficiency.Humic acid?HA?,anthracene hydroquinone-2,6-two sodium sulfonate?AHQDS?,anthraquinone-2-sodium sulfonate?AQS?are quinones which can promote the interaction between bacteria and azo dyes,This kind of material can be used as an electron shuttle in the process of anaerobic fermentation,which can accelerate the electron transfer in the process of bacterial metabolism.In addition,activated carbon can also be used as catalyst to promote the removal of dye molecules.This paper chooses Klebsiella oxytoca GS-4-08 as the main body of the decolorization of azo dye methyl orange,the effect of carbon activated carbon alone with Klebsiella compound,humic acid and iron loaded composite bacteria,and AQS of azo dye removal effect;also through the study of AQS,GAC,Fe-HA for bacterial tolerance,Finally,AQS was chosen as the best electron shuttle to investigate the effect of GS-4-08 on the anaerobic fermentation of Klebsiella oxytoca.The main research contents and conclusions are as follows:?1?1.5g·L^-1 HA was configured in the laboratory,the centrifuge was used to configure at 10000 g in 20 min to remove insoluble matter,adding 5 mmol·L^-1 FeSO₄-7H2 O,rapid mixing,adjusting pH=7,suspension static one week,and then repeat the centrifugal process,the precipitate was collected by freeze drying to get Fe-HA precipitates,Investigation and analysis of Fe-HA Klebsiella and oxytoca GS-4-08 composite degradation of azo dye methyl orange were conducted,found in 30 h,Fe,Fe-HA,bacteria in the blank composite under the condition of decoloration of methyl orange can respectively reach 62%,11%,52%,it can get some conclusion that Fe-HA has certain effect on bacteria tolerance.?2?The removal of azo dye methyl orange is researched by controlling the concentration of GAC,the results showed that the degradation process are in line with the first order kinetic equation in 2,5,8,10 g·L^-1;and the concentration of GAC is higher,the decolorization efficiency is higher,10g·L^-1GAC can decolorize 99% methyl orange within the 2h;8g·L^-1GAC can decolorize 99% methyl orange within the 2.75h;5g·L^-1GAC can decolorize 99% methyl orange within the 5h,2g·L^-1GAC can decolorize 99% methyl orange within the 10.5h;The degradation of 2g·L^-1GAC and composite bacteria before and after decolorization of methyl orange were consistent with two degradation kinetic equation,and the decolorization rate were 0.175 and 0.17,the difference is small,while strain death phenomenon was happened in complex reaction GAC and strain experiments after 10 h in the experimental reaction,indicating that GAC may affect tolerance strain decolorization of methyl orange.?3?by adding AQS into the bacterial anaerobic fermentation process,found the decolorization MO can reach 60% in the case of AQS without 25 h,and 0.08mmol·L^-1 AQS in 10 h MO was up to 100%,and the strain grew well in the anaerobic fermentation process of AQS,and the emergence of hydrogen producd in the anaerobic fermentation stage,so at the paper will focus on the promotion of AQS Klebsiella oxytoca GS-4-08 on hydrogen production by anaerobic fermentation.?4?The effect of different AQS concentration on the decolorization of methyl orange by Klebsiella oxytoca GS-4-08 was studied,It was analyzed that methyl orange decolorization kinetics,hydrogen production kinetics,sucrose degradation kinetics,and bacterial growth,and in the process of anaerobic digestion,mesophilic bacteria Klebsiella oxytoca GS-4-08 as a single strain of anaerobic fermentation,AQS as electron shuttle changing electron transfer rate,influence on electronic balance and energy conversion.The results show that Klebsiella oxytoca GS-4-08 can degrade sucrose to 92.2%?25h?,decolorize methyl orange?10h?to 100%,produce 2.33 mmol·L^-1 ethanol,2.35 mmol·L^-1 acetic acid,100.5 mL hydrogen in 0.1 mmol·L^-1AQS.Decolorization process of methyl orange conforms to the first-order kinetic equation,hydrogen production kinetics confirms to Gompertz dynamics.Electron yield is 90.5%,energy generation rate is 802 kJ·mol^-1sucrose.Therefore,using Klebsiella oxytoca GS-4-08 to produce at least two types biofuels via fermentation process seems to be feasible in future applications.