Progress in the application of dye wastewater treatment technology

Author：admin   Date：2017-12-09

Abstract: mainly explains the physical method of dye wastewater treatment technology in (adsorption method, membrane separation method) and chemical method (chemical coagulation, chemical oxidation, wet air oxidation, photocatalytic oxidation), biochemical method, electrochemical method, principle and characteristics of the recent research progress and application. The production process of dye waste water is large and complex, difficult to handle, infection governance costs are high, but fundamentally reduce pollution, is a permanent solution.
Core words: Dye Wastewater physical, chemical, chemical, biochemical and electrochemical methods
Textile dyestuff industry has developed rapidly in recent years. At present, the output of various dyes in China has reached 900 thousand T, and dye wastewater has become one of the most important sources of environmental infection. There are many varieties in the dyestuff industry, and the process is complex. The wastewater contains large amounts of organic matter with salt, have high CODCr, deep color, strong acid and alkaline etc, has always been a problem in wastewater treatment. This paper mainly describes the physical, chemical, electrochemical and biochemical methods of dye wastewater treatment technology, as well as the characteristics, principles and recent research progress and application of these technologies.
1 physical method
1.1 adsorption method
The adsorption method is the use of porous solids (such as activated carbon adsorption resin) contact with dye wastewater by adsorption of surfactant, the organic dye wastewater with adsorption of metal ions and concentrating on its surface, to purify water target.
Activated carbon has strong adsorption capacity, and has good adsorption function for cationic dyes, direct dyes, acid dyes, reactive dyes and other water-soluble dyes, but activated carbon is expensive, and it is not easy to regenerate. The dye adsorbent made from the mixture of chitosan and activated carbon and cellulose has excellent adsorption capacity for reactive dyes and acid dyes. The adsorption capacity is 264 and 421mg/g (the adsorption capacity of coconut activated carbon is less than 80mg/g). The adsorbents have excellent dispersibility in water and can be treated with simple and cheap contact filtration.
Macroporous adsorption resin is a polymer bead like body with a crosslinked network structure, with excellent pore structure and high specific surface area. Adsorption resins can be used for the removal of aromatic sulfonates, naphthol substances, which are difficult to be treated by biological treatment. It is easy to regenerate, and the physicochemical stability is good. Resin adsorption has become one of the effective methods to deal with dye wastewater.
1.2 membrane separation
Membrane separation technology should be used in the treatment of dye wastewater as the main if ultrafiltration and reverse osmosis. It is reported that the decolorization rate of vat dye wastewater by tubular and hollow fiber polysulfone ultrafiltration membrane is between 95% and 98%, the removal rate of CODCr is 60% to 90%, and the dye recovery rate is over 95%. In recent years, a new membrane material with chitosan ultrafiltration membrane and porous carbon membrane has been used to treat the printing and dyeing wastewater, and a better effect has been obtained. Xia Zhining studied the dye wastewater under ultrasonic action by cellulose acetate membrane permeability with salt permeability, it is found that the ultrasound significantly accelerates mass transfer to "concentration polarization" role in membrane separation, sonication time and its permeability is 1.5 times without ultrasonic, a greater impact on salt permeability the retention rate, respectively 94% and 67%.
2 chemical method
2.1 chemical coagulation method
The chemical coagulation method mainly includes the precipitation method and the gas float method. This method is economical and effective, but the chemical sludge needs to be further treated. It is commonly used as a compound of inorganic iron. In recent years, the increasing number of polymer coagulants has been adopted at home and abroad. Natural polymer flocculant mainly starch and starch derivatives, chitin derivatives with lignin derivatives 3 categories. Ceng Shulan and other NaOH used as catalyst to produce cationic starch CST from corn starch and etherification agent M. When the dosage is 7 to 15mg/L, the decolorization rate of acid dyes and reactive dyes is over 90%. Wu Bingyan prepared by grafting polymerization of lignin quaternary ammonium salt flocculant J acid dye wastewater, sulfonic acid groups in the Ji An generation flocculant in the wastewater with ion water insoluble substances, the dosage of 20mg/L, the color removal rate was 90%.
Fang Xin Lan using shrimp, crab shell for treatment of printing and dyeing wastewater as raw materials to prepare chitosan, CODCr removal rate reached more than 85%. Natural polymer flocculants are small in charge density and low in molecular weight. They are easy to be biodegraded and lose flocculation activity. The synthetic organic polymer flocculants have large molecular weight, many functional groups in the molecular chain, good flocculation performance, less dosage and wide range of pH. The representative artificial organic polymer flocculant has PAN- DCD (two cyanogen two amine modified polyacrylonitrile polyelectrolyte), Wx series macromolecule Decolorizing Flocculant, PDADMA-A (two methyl diallyl ammonium chloride polymer) M.
2.2 chemical oxidation method
Chemical oxidation is the use of ozone, chlorine, and its oxide to destroy the chromophore of the dye and decolorizing. The ozone oxidation method can obtain good decolorization effect for most dyes. But the effect of the dyes, such as vulcanization, reduction, and other insoluble dyes, is poor. Fenton reagent oxidation process, the essence of its decolorization is the hydroxyl radical produced by the reaction of H2O2 and Fe2+ to break the chain of dye organic matter. In addition to oxidation, Fenton reagent also has coagulation. The research shows that this method can be used to treat 2- naphthalene sulfonate wastewater. First, it is coagulated and precipitated with FeCl3, then 60min and CODCr99.6% can be removed by oxidizing 60min with H2O22g/gCODCr and Fe2+4g/L water at pH1.5 ~ 2.5.
2.3 wet air oxidation method
Wet air oxidation (WAO) is used in high temperature (125~320), high pressure (0.5 ~ 20MPa) into the air, so that the organic matter in the wastewater is directly oxidized to [20]. Supercritical water oxidation (SCWO) refers to the critical temperature (374 degrees C) and critical pressure (22.05MPa) conditions when the temperature and pressure are higher than the water.