Studies On Biodegradability Of Vat Dyes

As the development of dyes,there are abound of man-made dyes gaining acess to the environment,a part of them can be biodegrated by the microorganism in the wastewater or in the soil,but because of that most of the dyes have the different chemical structure from the natural organism ,so at present there is not a very effective microorganism system that can biodegrate these dyes. Because of the biodegradeability is poor,so the dyes is threat the human's environment and healthy. Around the studies of these problems,the biodegradeability of the dyes is still a considerable factor.Vat dyes have many styles,and kinds of colours,beside ,they have high grade color fastness. They are not only applied in cotton fiber and rayon fiber,but also used in other mixed-fiber,and more,through a few treatment,it can be changed to organic color and enlarge its applied field. In the drastic competition between active dyes,direct dyes and vat dyes,because of its inherent features,the vat dyes is also a kind of dyes.In this reseach, we selected the mainly used 14 vat dyes of 5 kinds as the object of study .We test their aerobic degradation by way of BOD₅/COD and microbiological respiratory rate test,and study their anaerobic degradation by way of the microbiological respiratory rate test of the upper clearified liquid. And then we treat one kind of dye wastewater by the processs of anaerobic-aerobic.Under the aerobic condition,the aerobic degradation of the 14 vat dyes are poor. And we can see from the respiratory rate curve that only vat blue BO dye's degradation is good,and there are 3 vat dyes(vat black RB,vat green FFB,vat red GG) can be degraded under low concentration,but their biodegradation are poor. By comparision of relative value of B/C,we find that the biodegradation of the vat dyes have the intimate relation with their structures. From 14 kinds of chosen dyestuff,we can get the result: the biological performance of anthraquinone,anthrone,carbazole anthraquinone,heteronuclearketone,composite dyes is lower in turn.The dye with symmetrical texture is easily biodegradated and with heavier molecular is relatively poorer. Besides,the type and amount of the substituted radical on the aromatic cyclic of the dyes also affect the biodegradation. Generally, the promotional radical will enhance the biodegradation,while the inhibitory radical let the aromatic cyclic more stable. If there are more promotional radicals on the dye aromatic cyclic,the dye will be degraded easily and the inverse circumstance , the dye will be degraded hardily. The test of biodegradation of the dyes under anaerobic condition show that the 14 vat dyes can be degraded after a few time's of anaerobic reaction .All of which show that the anaerobic process is very important in improving the biodegradation of the dye wastewater.We treat the simulate wastewater of vat blue BO by anaerobic-aerobic processs, from which we find anaerobic process is key to the color removal and biodegradability improvement . And with the operation of the reactor the good treatment effect will be available after it level off.This paper about the biodegradation of thevat dyes and its conclusions can not only provide basis for the biotreatment of the vat dye wastewater, but offer reference for the production and use of the vat dyes and the exploitation of environmental protected dyes.