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Abstract: The state and progress in the treatment technology of dyeing wastewater are summarized in this paper, especially the new treatment technologies coming about in the latest years. The developing trend of treatment for organic matters is discussed as well.
Key words: Refractory; Dyeing Wastewater; Wastewater Treatment
In recent years, the textile printing and dyeing industry in Zhejiang province has given rise to a serious pollution to the ecological en
Because all types of dyes such as hydrophobic dye, hydrophilic dye, cationic dye, and anionic dye are contained in the wastewater that is produced from printing and dyeing mills and also there are too many and complex types of intermediates, the mixed wastewater treatment turns to be rather difficult from the perspective of technology. In the meantime, the uptake rate of the dye products that are made by the domestic manufacturers is generally low, and excessive additives are added by the printing and dyeing production and processing enterprises into their products more or less, thus giving rise to a large amount of surplus dyes in the dyeing process. This will not only result in the waste of resources, but also make the pollution of each dye product nearly twice as many as that of the developed countries.
2.3 Difficult to Degrade the Increasing Concentration of Organic Compounds
The wide application of the chemical pulps polyvinyl alcohol (PVA) and sodium carboxy methyl cellulose (CMC), the artificial silk saponification matter and many new accessory ingredients as well as the Dacron-contained hydrolysate produced from the alkali weight reduction process of Dacron imitated silk fabrics and the alkali weight reduction wastewater of the compounds such as phthalic acid and ethylene glycol.
3 Current Situation of the Studies of New technologies
In recent years, a series of new technology studies focusing on how to treat the printing and dyeing wastewater economically and efficiently he been made by both domestic and foreign experts. The current situation of the studies of new technologies can be mainly concluded as follows.
In recent years, the micro-electrolysis emerged. Its working principle is as follows: in the water solution containing acid electrolytes, countless tiny primary batteries are formed between scrap iron and carbon particles and also an electric field with a powerful reducing capacity is composed in their action space, making some organic matters of oxidation state restored to original state and thus improving biochemical properties of wastewater. Therefore, this method is feasible for the treatment of printing and dyeing wastewater with low concentration and a all number of molecular.
3.6 High
High-energy physics method is an emerging water treatment process. In the treatment of the printing and dyeing wastewater, the high-energy physics method features a high removal rate of organic matter, covering a all area, and simple operation. However, its disadvantages are also in existence, such as too expensive for producing high-energy particles, high technical requirements, large energy consumption, and low energy utilization rate. Therefore, to really put this method into the actual practice, it is still necessary to do a lot of research work.
3.7 Photo-Fenton and Electro-Fenton Coupling Method
Fenton reagent, because of its powerful oxidizing, has been applied by increasingly more people in removing the organic pollutants from water. In essence, the powerful oxidizing function of the Fenton reagent is that H2O2 can efficiently decompose and generate the hydroxyl free radicals (·OH) of powerful oxidizing function and high electro-negativity or electron affinity (569.3 kJ), and ·OH has the ability to oxidize and degrade the organic pollutants in water, making them ultimately mineralized into matter of all molecules such as CO2, H2O and inorganic salts. However, there are some shortcomings in the traditional Fenton method [19]: (1) it is necessary to add Fe2+ and H2O2 on site, making medicament low higher; (2) H2O2 added in the reactor can be decomposed into water and oxygen, making oxidant wasted; (3) another drawback caused by the random adding is that a large amount of OH· can be produced at the beginning of reaction and the organic matters canbe mineralized completely, but the amount of OH OH· will be less and less along with the proceeding of reaction, making organic matters not degraded thoroughly; (4) it is possible to give rise to a secondary pollution.In comparison with the traditional Fenton method, the Photo-Fenton method that was developed in the 1980s had its own unique features, which can make up the shortcomings of the traditional Fenton mentioned above.
The Electro-Fenton method, as a combination process, has been increasingly more popular in the world because of its multiple advantages such as H2O2 production, high H2O2 utilization rate, low cost, and easy operation. In theElectro-Fenton process, the hydrogen peroxide, which is continuously generated from the reduction reaction of dissolved oxygen molecules on negative electrode surface, is used to he a Fenton reaction with Fe2 + to generate Fe3 +, which is reduced to Fe2 + in the negative electrode and continues to he a Fenton reaction with H2O2. The basic reaction mechani [20, 21] can be simply expressed as follows.
O2 + 2H+ + 2e→H2O2 (1)
Fe2 + +H2O2 →Fe3 + +OH- + ·OH (2)
·OH +RH (organic matter) →P (catabolite) (3)
In the Electro-Fenton oxidation method, a UV lamp is introduced in the Photo-Fenton reactor, and then the Electro-Fenton reaction makes the organic matters efficiently degraded under the action of UV-light because of the cooperation between the photo-reduction of iron ions and the photo-radiation decomposition of hydrogen peroxide. Compared with the Electro-Fenton method, the prominent advantage of the photo-Fenton is that the introduction of UV-light can induce and generate a large amount of ·OH, making an improvement to the current utilization efficiency. Therefore, the treatment effect of the photo-Fenton method is better than that of the Electro-Fenton method [22].
At present, many difficult new technologies for the treatment of the printing and dyeing wastewater are still in the explorative experimental stage. Therefore, to attain a large scale of industrial application, it is still necessary to solve many problems such as the in-depth researches of reaction mechanis, the optimized combination of all processes, the design of larger reactors, etc.
16.Lecheng Lei, Dajiang Wang. Study on the Advanced Oxidation of Polyvinyl-Alcohol by the Photo-Fenton Reaction [J]. Acta Scientiae Circumstantiae, 2000, 20 (2): 53-59.
17.Zhan Qian, Chaohai Wei, Yaping Zhang, et al. Study on Degradation of Reactive Brilliant Orange X-Gn by Uv/Fe3+/H2o2 System [J]. Environmental Chemistry, 2006, 25(2): 194-198.
18.Lianjun Zhang, Fucai Yin, et al. Study on the Biodegradability of Printing and Dyeing Wastewater by Ultrasonic We [J]. Anhui Chemical Industry, 2007, 8(4): 50-52.
19.[19] Hua Xiao, Rongfeng Zhou. Current Ele
20.Zhang Hui, Chol Heung-jin, Huang Chin-pao. Optimization of Fenton Process for the Treatment of Landfill Leachate. Hazard. Mater. , 2005, 125 (3): 166～174.
21.Fang Zhang, Guangming Li, Xiuhua Zhao, et al. Study Status and Progress in Wastewater Treatment by Electro-Fenton Method. Industrial Wastewater Treatment, 2004, 24 (12): 9-13.
22.Ahmet Altin. An Alternative Type of Photoelectron-Fentonp rocess for the Treatment of Landfill Leachate. Sepn. and Pu-rifn. Technol, 2008, 61: 391-397.
Key words: Refractory; Dyeing Wastewater; Wastewater Treatment
1 Introduction
The beauty of south China is originated from water. At the present stage, the current water resource in Zhejiang province which is located in south China is less than 2000 square meters, which has been closer to the internationally-recognized water stress warning level (1700 cubic meters). In the meantime, regional and water-quality water shortages he also been proven to be the bottlenecks for imposing restrictions on the development of the society and economy after land and energy.In recent years, the textile printing and dyeing industry in Zhejiang province has given rise to a serious pollution to the ecological en
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vironment as well as the water environment when promoting the rapid development of the local places . The survivals of the fish and other kinds of aquatic organis he been threatened by the printing and dyeing wastewater. Besides, the organic matters, which are drowned in the bottom of water, will produce harmful gases such as hydrogen sulfide and make environment deteriorated because of the anaerobic digestion. Most of the dyeing and printing wastewater is alkaline, and thus will make soil salinizated after entering croplands; the color luster of printing and dyeing wastewater is generally dark, which can seriously affect the appearance of water .2 Problems and Difficulties
There are a great number of problems and difficulties in the printing and dyeing wastewater treatment technologies. These problems and difficulties can be mainly concluded from the several respects in the following.2.1 Difficult to degrade COD
In treatment technology, the dyeing wastewater mainly comprises of organic matters and can be biochemical from the perspective of theory in most cases, but the BOD and COD ratios in the quality of the dyeing wastewater are generally low, and therefore it is not so easy to be biochemical although it can be. At the same time, it is also not so easy for the activated sludge in the aeration tanks to domesticate and adapt to the wastewater of the changing-over dye intermediates, thus playing an effect on the biological degradation ability.2.2 Difficult toDiscolor the High-colored WastewaterBecause all types of dyes such as hydrophobic dye, hydrophilic dye, cationic dye, and anionic dye are contained in the wastewater that is produced from printing and dyeing mills and also there are too many and complex types of intermediates, the mixed wastewater treatment turns to be rather difficult from the perspective of technology. In the meantime, the uptake rate of the dye products that are made by the domestic manufacturers is generally low, and excessive additives are added by the printing and dyeing production and processing enterprises into their products more or less, thus giving rise to a large amount of surplus dyes in the dyeing process. This will not only result in the waste of resources, but also make the pollution of each dye product nearly twice as many as that of the developed countries.
2.3 Difficult to Degrade the Increasing Concentration of Organic Compounds
The wide application of the chemical pulps polyvinyl alcohol (PVA) and sodium carboxy methyl cellulose (CMC), the artificial silk saponification matter and many new accessory ingredients as well as the Dacron-contained hydrolysate produced from the alkali weight reduction process of Dacron imitated silk fabrics and the alkali weight reduction wastewater of the compounds such as phthalic acid and ethylene glycol.
3 Current Situation of the Studies of New technologies
In recent years, a series of new technology studies focusing on how to treat the printing and dyeing wastewater economically and efficiently he been made by both domestic and foreign experts. The current situation of the studies of new technologies can be mainly concluded as follows.
3.1 Catalytic Wet Air Oxidation Method
Wet air oxidation is a way of oxygenizing or deoxidizing the water-dissolved or suspended organic matters by using oxygen or air as the oxidant in liquid phase at high temperature and high pressure [3]. The catalytic wet oxidation method, which is developed on the basis of the traditional wet摘自：毕业论文提纲范文www.udooo.com
oxidation method, has the ability to promote reactions to be complete in more moderate conditions and a shorter time. Specifically, the main principle of the catalytic wet air oxidation is adding solid or liquid catalysts in the traditional wet oxidation process for the purpose of reducing the temperature and pressure that are demanded by the reactions and also making an improvement to oxidative decomposition ability and shortening thetime.3.2 Electrochemical Method
Electrochemical method is to implement electrolytic oxidation and flocculent settling (i.e. electrolytic method and electro-air-flotation method) on dye molecules under the effect of electric field effect by using the iron plate, graphite and aluminum sheet as electrodes and the salt in salt-contained wastewater solution as conductive medium. This method can play a good role in discoloring the low-concentration active dyes and the soluble dye wastewater, etc. According to the reports, the discoloring rate can be higher than 80%, the COD removal rate can reach 40%, and also the biochemical property of wastewater can be greatly improved if this method can be applied in the treatment of the printing and dyeing wastewater [4-7].In recent years, the micro-electrolysis emerged. Its working principle is as follows: in the water solution containing acid electrolytes, countless tiny primary batteries are formed between scrap iron and carbon particles and also an electric field with a powerful reducing capacity is composed in their action space, making some organic matters of oxidation state restored to original state and thus improving biochemical properties of wastewater. Therefore, this method is feasible for the treatment of printing and dyeing wastewater with low concentration and a all number of molecular.
3.3 Photo-catalytic Oxidation Method
The photo-catalytic oxidation process features easy-to-operate, no secondary pollution, ability to completely mineralizing the organic matters, etc. The most representatives mainly include the advanced oxidation technology and the advanced Fenton technology that people he paid increasingly more attention to in the treatment of the printing and dyeing wastewater [8-17].3.4 Membrane Reactor
Reverse oosis method is to make the wastewater discolored by selectively getting rid of the solutes in wastewater via a semi-permeable membrane. Membrane bioreactor is an emerging wastewater treatment and recycling process. It has the ability to not only highly effectively separate solid liquid and also directly acquire recycling water by replacing the secondary sedimentation tanks in the normal activated sludge with a membrane separation devic摘自：毕业论文 格式www.udooo.com
e. Besides, the interception performance of the membrane is helpful for maintaining the microorgani quantities of high concentration within a biological reactor, and thus the capacity load of the treatment devices canbe greatly improved and also the floor area can be efficiently sed.3.5 Ultrasonic Technology
The principle of the method is as follows: the wastewater enters an air we vibration room after added with the selected flocculating agent via a balance tank; a part of organic matters of the wastewater is spaced into all molecules under an intense vibration with rated vibration frequency, and the flocculating agent is quickly flocculated under the thermal motion of the accelerated water molecules and subsequently color, COD & aniline concentration fall. Therefore, this method can play a role in reducing the concentration of the organic matters in wastewater. At present, great results he been achieved in the studies of ultrasonic technology in water treatment. However, the majorettes of studies are still limited to the level of laboratory [18].3.6 High
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-energy Physics MethodHigh-energy physics method is an emerging water treatment process. In the treatment of the printing and dyeing wastewater, the high-energy physics method features a high removal rate of organic matter, covering a all area, and simple operation. However, its disadvantages are also in existence, such as too expensive for producing high-energy particles, high technical requirements, large energy consumption, and low energy utilization rate. Therefore, to really put this method into the actual practice, it is still necessary to do a lot of research work.
3.7 Photo-Fenton and Electro-Fenton Coupling Method
Fenton reagent, because of its powerful oxidizing, has been applied by increasingly more people in removing the organic pollutants from water. In essence, the powerful oxidizing function of the Fenton reagent is that H2O2 can efficiently decompose and generate the hydroxyl free radicals (·OH) of powerful oxidizing function and high electro-negativity or electron affinity (569.3 kJ), and ·OH has the ability to oxidize and degrade the organic pollutants in water, making them ultimately mineralized into matter of all molecules such as CO2, H2O and inorganic salts. However, there are some shortcomings in the traditional Fenton method [19]: (1) it is necessary to add Fe2+ and H2O2 on site, making medicament low higher; (2) H2O2 added in the reactor can be decomposed into water and oxygen, making oxidant wasted; (3) another drawback caused by the random adding is that a large amount of OH· can be produced at the beginning of reaction and the organic matters canbe mineralized completely, but the amount of OH OH· will be less and less along with the proceeding of reaction, making organic matters not degraded thoroughly; (4) it is possible to give rise to a secondary pollution.In comparison with the traditional Fenton method, the Photo-Fenton method that was developed in the 1980s had its own unique features, which can make up the shortcomings of the traditional Fenton mentioned above.
The Electro-Fenton method, as a combination process, has been increasingly more popular in the world because of its multiple advantages such as H2O2 production, high H2O2 utilization rate, low cost, and easy operation. In theElectro-Fenton process, the hydrogen peroxide, which is continuously generated from the reduction reaction of dissolved oxygen molecules on negative electrode surface, is used to he a Fenton reaction with Fe2 + to generate Fe3 +, which is reduced to Fe2 + in the negative electrode and continues to he a Fenton reaction with H2O2. The basic reaction mechani [20, 21] can be simply expressed as follows.
O2 + 2H+ + 2e→H2O2 (1)
Fe2 + +H2O2 →Fe3 + +OH- + ·OH (2)
·OH +RH (organic matter) →P (catabolite) (3)
In the Electro-Fenton oxidation method, a UV lamp is introduced in the Photo-Fenton reactor, and then the Electro-Fenton reaction makes the organic matters efficiently degraded under the action of UV-light because of the cooperation between the photo-reduction of iron ions and the photo-radiation decomposition of hydrogen peroxide. Compared with the Electro-Fenton method, the prominent advantage of the photo-Fenton is that the introduction of UV-light can induce and generate a large amount of ·OH, making an improvement to the current utilization efficiency. Therefore, the treatment effect of the photo-Fenton method is better than that of the Electro-Fenton method [22].
At present, many difficult new technologies for the treatment of the printing and dyeing wastewater are still in the explorative experimental stage. Therefore, to attain a large scale of industrial application, it is still necessary to solve many problems such as the in-depth researches of reaction mechanis, the optimized combination of all processes, the design of larger reactors, etc.
4 Conclusion
At present, energy conservation and emission reduction he proven to be very important tasks for the governments at all levels. Zhejiang province is striving for the goal of constructing an ecological province. However, correctly dealing with the relationship between the源于：论文怎么写www.udooo.com
economic growth and the energy conservation and emission reduction is a problem, which is necessary to be solved in the development of all industries. In the meanwhile, taking bold measures and solving wastewater treatment and recycled water problems through technical research and policy guidance are important tasks for the printing and dyeing enterprises at present, and also very urgent for protecting water resources, realizing the sustainable development, and constructing a harmonious society. Therefore, the development of the effective, economic high and composite technologies for the treatment of the difficultly-degradable printing and dyeing wastewater has a wide application prospect.源于：论文致谢范文www.udooo.com
15.Kuo W G. Decolorizing Dye Wastewater with Fenton Reagent [J].Wat Res., 1992, 26(7):881-886.16.Lecheng Lei, Dajiang Wang. Study on the Advanced Oxidation of Polyvinyl-Alcohol by the Photo-Fenton Reaction [J]. Acta Scientiae Circumstantiae, 2000, 20 (2): 53-59.
17.Zhan Qian, Chaohai Wei, Yaping Zhang, et al. Study on Degradation of Reactive Brilliant Orange X-Gn by Uv/Fe3+/H2o2 System [J]. Environmental Chemistry, 2006, 25(2): 194-198.
18.Lianjun Zhang, Fucai Yin, et al. Study on the Biodegradability of Printing and Dyeing Wastewater by Ultrasonic We [J]. Anhui Chemical Industry, 2007, 8(4): 50-52.
19.[19] Hua Xiao, Rongfeng Zhou. Current Ele
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ctro-Fenton Research Situation and Development. Shanghai Environmental Science, 2004, 23(6): 253.20.Zhang Hui, Chol Heung-jin, Huang Chin-pao. Optimization of Fenton Process for the Treatment of Landfill Leachate. Hazard. Mater. , 2005, 125 (3): 166～174.
21.Fang Zhang, Guangming Li, Xiuhua Zhao, et al. Study Status and Progress in Wastewater Treatment by Electro-Fenton Method. Industrial Wastewater Treatment, 2004, 24 (12): 9-13.
22.Ahmet Altin. An Alternative Type of Photoelectron-Fentonp rocess for the Treatment of Landfill Leachate. Sepn. and Pu-rifn. Technol, 2008, 61: 391-397.