Infuence Of Fatliquor And Aromatic Tannin On The Degradation Of Dyes

Biodegradation of leather chemicals have received much attention in recent years,because the application of harmless and biodegradable chemicals is essential for tanningenterprises to seek market development space. The researches on the biodegradation ofleather chemicals to be present in the co-substrates have two purposes. The predictionsof residual concentrations of leather agents after the wastewater treatment are moreaccurate. And on the other hand, these results could provide some theories for themolecular design of more environmental leather chemicals.Dyes contribute as one of the most important pollutions in the tannery wastewater,and which contains complex aromatic molecular structures. Moreover, Remnants of thedyes can reduce the transmittance of the effluents and result in changing themircoorganic species even in the small concentrations. The current state of the art forthe bio-treatment of the dyes mainly depends on two processes which are the anaerobicazo-reduction and aerobic adsorption. By contrast with other leather chemicals,fatliquor is biodegraded easily, and it has a potential of to provide effective carbon andenergy for the degradation of the dye.In this paper, variously commercial fatliquors contribute as the experimental object,and the influence of fatliquors on the dye degradation had been measured. The resultsshow that under aerobic conditions, the easily degraded fatliquors are able to improvethe biological growth, and lead to enhance the dye adsorption of the active sludge.Under anaerobic conditions, Fatliquor with phosphate groups leads to a considerablegrowth phosphate accumulating bacteria. And the synthesis of poly-hydroxybutyrate(PHB), which is product by these phosphorus accumulating bacteria under anaerobicconditions, competes for the reduction state of nicotinamide adenine dinucleotide(NADH) and reduced state flavin (FADH2) with the reduction of azo dyes. Therefore,the degradation of the dyes was inhibited completely. Moreover, the dose-responserelationship of these fatliquors to inhibit the dye degradation is in accordance withMonod model. Acid fuchsin6B as the experimental material, Emax and K values ofLecithin fatliquor to inhibit the dye degradation were-0.597days-1and212.503mg/Lrespectively, and Emax and K values of Phosphoric esters fatliquor to inhibit the dyedegradation were-0.510days-1and170.573mg/L respectively. Easily degradedfatliquors without phosphate groups could improve the reduction of azo dyes due to a numerous formation of NADH and FADH2in the degradation of these fatliquor, andthereby improve the anaerobic dye degradation. Moreover, the dose-responserelationship of these fatliquors to improve the dye degradation is in accordance withMoser model. Acid fuchsin6B as the experimental material, Emax, K and n values ofSulfonated fatliquor to improve the dye degradation were0.491days-1,667.981mg/Land6.053respectively. And Emax, K and n values of Oxidized-sulfited neat’s foot oilto improve this dye degradation were0.436days-1,467.088mg/L and8.311respectively.And Emax, K and n values of Oxidized-sulfited fish oil to improve this dyedegradation were0.626days-1,645.914mg/L and3.017respectively. WhenOxidized-sulfited neat’s foot oil contributed as the co-substrates,40kinds of commercialleather dyes had been improved on the decolorization activities in certain degree.Mineral oil-based fatliquors are hardly bio-degreded, which have neitherimprovement nor inhibition on the dye decolorization. However, fatliquors with cationicgroups have a certain bio-toxicity, with the consequence that they could inhibit the dyedecoloriation. By contrast with the fatliquor with phosphate groups, the inhibitions ofthese fatliquors with cationic groups are a little.The white-rot fungi are able to degrade dyes under aerobic conditions, and detoxifythe biological toxicity of dyes. In this paper, a white-rot fungus had been isolated fromthe local enviro nment and was named as Y. Fungus. And the potential of the isolatedfungus for effective decolorization of azo dyes had been evaluated. Nine kinds ofcommercial dyes as the experimental objects, under the aerobic conditions, after48hours of the cultures all of these dyes were decolorized by Y. Fungus in obvious degrees.Optimum enviro nmental factors of Y.Fungus to decolorize the dye are4.5pH,40℃and100rpm of the shaking frequency. Y.Fungus also has a strong ability to degradehigh concentrations of dyes. When the initial concentrations of Direct Fast Bordeauxand Acid Red74are lower than100mg/L, the degraded concentrations of the two dyesrose linearly with the increase of the initial concentrations of the dyes. The degradationof the dyes by the white-rot fungi attribute to lignin degrading enzymes, which arethought to be expressed in most cases only during secondary metabolism followinggrowth when carbon and/or nitrogen sources become limited. And therefore there is aretaining time in the degradation of dyes by Y.Fungus. The retaining times of Acid Red74and Direct Black38are6.074hours and6.047hours respectively. According to thecharacteristics of the white-rot fungi, the aromatic tannins may affect the degradation ofdyes by the white-rot fungi. Four kinds of vegetable tannins and a synthetic tanningagent with phenolic aldehyde as the co-substrates, the decolorization activities of Acid Red74in various cultures had been measured. The results showed that4kinds of thetannins except the tannin extract of betelnut had inhibited the dye decolorization ofY.Fungus, and the inhibition of the synthetic tanning agent with phenolic aldehyde is themaximum. According to the activities of lignin degrading enzymes, the inhibition of thevegetable tannins on the decolorization activity is mainly due to the competition for theenzymes between the tannins and the dye, whereas the synthetic tanning agent competethe enzymes with the dye and inhibits the synthesis of the enzymes that result in theinhibition on the decolorization. Moreover, when the four kinds of vegetable tanninscontribute as the co-substrate, with an increase in the initial concentration of the dye,the inhibitions of the vegetable tannins on the dye decolorization also are increased.And Quebracho extract and the synthetic tannin as the co-substrate, with the increase inthe initial concentration of the tanning agents, the inhibitions of the vegetable tannins onthe decolorization of AR47also are increased.