Background and overview
Dyes synthesized with hydrazine or its derivatives, or dyes having a fluorene structure in the dye molecule are called anthraquinone dyes (such as 2-Methylanthraquinone). These dyes account for about 20% of synthetic dyes. They can be further classified into acid dyes, disperse dyes, vat dyes, direct dyes and reactive dyes according to application properties and application methods. Anthraquinone dyes (such as 2-Methylanthraquinone) are currently the second most widely used dyes. It has two main advantages: one is excellent in light fastness, and the other is to produce bright colors. In dark dyes of red, purple, blue and green, anthraquinone dyes (such as 2-Methylanthraquinone) are irreplaceable. The important position. Moreover, dark dyes are dominated by anthraquinone dyes, especially for high-end lightfast dyes, such as 2-Methylanthraquinone. Despite this, in the study of the relationship between the light fastness and the structure of anthraquinone dyes (such as 2-Methylanthraquinone), more attention is paid to the light fastness problem of commercial anthraquinone dyes (such as 2-Methylanthraquinone), different dyes. The use of complexing to obtain good color fastness is a hot topic of current research. However, since commercial dyeing is usually a mixture of several chemical structures, it is difficult to make a reliable comparison of the obtained fastness data. There are many factors affecting the light fastness of anthraquinone dyes (such as 2-Methylanthraquinone), such as the impurities remaining in the dye, the type of fiber, the additives in the dyebath, the environment in which the fibers are located, and the degree of aggregation of the dye on the fibers. Wait.
Light fading mechanism and mode
The light fastness of an anthraquinone dye (such as 2-Methylanthraquinone) depends mainly on the molecular structure of the dye itself. The photofading process of anthraquinone dyes is a very complicated process. For example, in the aerobic condition, the most important stage of photofading is to form a hydroxylamine compound, and then continue to deep oxidation; in addition, dealkylation occurs, and fiber reddening occurs. It is generally believed that the higher the density of the amino electron cloud, that is, the stronger the basicity of the amino group, the easier it is to oxidize to hydroxylamine, and the lower the light fastness of the dye. Therefore, if an electron withdrawing group is introduced in the ortho position of the amino group, the amino group is lowered. The electron cloud density and the light fastness of the dye will increase.
When studying the light fastness of the substituted aminoguanidine, it was found that the light fastness of the dye is linear with the basicity of the amino group on the anthracene ring. If the introduced substituent increases the electron density of the N atom on the amino group, the amino group The alkalinity enhances the light fastness of the dye; on the contrary, it improves the light fastness of the dye. There are usually three modes for the fading process of anthraquinone dyes: (1) the change of the UV-visible absorption curve of the dyed fibers before and after fading is small, and the peak shape of the absorption curve does not change; (2) The absorption curve of the fibers before and after fading The size of the change is large, and the peak shape of the absorption curve changes little; (3) the size and peak shape of the absorption curve of the fiber before and after fading vary greatly. In the three fading modes, the order of change in dye light fastness is (1)>(2)>(3).
At present, the treatment methods of domestic and foreign anthraquinone dyes (such as 2-Methylanthraquinone) wastewater mainly include physical methods, biological methods, and chemical methods. In view of the development of domestic and foreign technology, the degradation methods of bismuth dyes (such as 2-Methylanthraquinone) are far ahead of the domestic. In the 1970s, Japan, Russia and the United States carried out advanced hydrazine dye wastewater. In the study of electron beam decolorization treatment, various degradation methods for anthraquinone dyes (such as 2-Methylanthraquinone) have matured in the 1990s, and in the late 1990s, anthraquinone dyes (such as 2-Methylanthraquinone) gradually appeared. Wastewater degradation methods, mainly concentrated on simple treatment methods such as coagulation and traditional biology. In recent years, emerging microbial adsorption or degradation methods in biological treatment, emerging adsorbents in physical treatment, and chemical treatments have gradually emerged. Advanced oxidation method.
The physical methods commonly used in the treatment of anthraquinone dyes (such as 2-Methylanthraquinone) are adsorption, membrane separation, and extraction.
1) Adsorption method. The adsorption method utilizes the porous solid to contact with the dye wastewater for adsorption, and does not need to add any chemicals, and no sludge is produced. US608406A uses activated carbon to adsorb anthraquinone dyes (such as 2-Methylanthraquinone), which has strong adsorption capacity but is not easy to regenerate. The CN1280102A solves the above regeneration problem by resin adsorption, and the resin is desorbed and regenerated, and can be reused. Subsequently, there have been a variety of adsorbents for waste treatment and waste reduction, CN103464090A, CN103406105A, CN103657592A, CN103922433A, CN105498716A and CN105618000A, etc. The adsorption speed is fast, the dosage is small, and there is no secondary pollution.
2) Membrane separation method. Membrane separation technology applied to dye wastewater treatment is mainly ultrafiltration, nanofiltration and reverse osmosis, high efficiency and environmental protection. In 1987, JPS62186986A used ultrafiltration membranes to treat hydrazine dyes (such as 2-Methylanthraquinone) wastewater with high removal rates. Subsequently, the technology has been widely used, but there are still shortcomings such as requiring special equipment, high investment, and easy fouling of the membrane. Based on this, CN103449572A solves the above problems by electrically modifying the traditional neutral ultrafiltration membrane by using an effective chemical reaction to obtain charged ultrafiltration membranes of different spacer lengths.
3) Extraction method. The extraction method utilizes the difference in solubility between an anthraquinone dye (such as 2-Methylanthraquinone) in water and an organic solvent to rapidly transfer the dye from the water to the solvent phase, which has the advantage that the extractant can be recycled after being regenerated.
2. Biological Method
1) Traditional biological treatment. The biological methods for treating hydrazine dyes (such as 2-Methylanthraquinone) wastewater are mainly aerobic and anaerobic methods. However, due to the lack of a single biological method, most of the anaerobic-aerobic combination processes are currently used. In order to improve the treatment efficiency, CN1958477A uses a modified anaerobic-aerobic cycle method to treat hydrazine wastewater. The purpose of continuous circulation is to make the anaerobic and aerobic biological groups in a suitable water environment and improve the degradation efficiency.
2) Emerging microbial/bacterial adsorption or degradation methods. In recent years, a large number of reports have been reported at home and abroad on the use of bacteria, fungi and genetically engineered bacteria to treat anthraquinone dyes by adsorption or degradation, with strong pertinence and good treatment effect. The bacterial species used in the hydrazine dye wastewater are mainly distributed in Aeromonas, Pseudomonas, and Bacillus. Anthraquinone dyes (such as 2-Methylanthraquinone) are mainly distributed in Penicillium, Rhodotorula, Aspergillus, Cephalosporium, Trametes, Geotrichum and the like. The treatment of anthraquinone dyes (such as 2-Methylanthraquinone) wastewater by using Aspergillus oryzae, Pseudomonas aeruginosa, P. chrysosporium, etc., has a high removal rate. Although a variety of microbial strains have been screened to degrade anthraquinone dyes (eg 2-Methylanthraquinone), some
The strain is still difficult to adapt to the environment and cannot meet the degradation requirements. Therefore, the degrading gene is transferred into or cloned into the strain to construct a genetic engineering bacteria.
3. Chemical Method
Common chemical methods for hydrazine dyes (such as 2-Methylanthraquinone) wastewater include coagulation, chemical oxidation, and advanced oxidation.
1) Coagulation method. Coagulation is commonly used for pretreatment or advanced treatment of anthraquinone dyes such as 2-Methylanthraquinone. Commonly used flocculants are aluminum salts and iron salts, and the treatment effect is good.
2) Chemical oxidation method. The chemical oxidation method is to oxidize and degrade pollutants by an oxidizing agent, and the commonly used oxidizing agents include ozone, hydrogen peroxide, sodium hypochlorite, chlorine dioxide and the like. For example, CN101412571A uses the Fenton method to degrade disperse blue, and the removal effect is good. However, since the pH needs to be adjusted to be acidic before the Fenton process, the weak alkalinity needs to be adjusted after the treatment to complete the agglomeration, the consumption of the agent is large, and sludge is generated. Therefore, CN103241826A uses a weak magnetic field to strengthen the H2O2-FeO Fenton reaction. The treatment of hydrazine dyes (such as 2-Methylanthraquinone) wastewater overcomes the shortcomings of the traditional Fenton process, has a high reaction rate, and has a wider pH range.
3) Advanced oxidation method. The advanced oxidation technology mainly includes wet oxidation method, electrochemical oxidation method, photocatalytic oxidation method, plasma method and electron beam method, etc., and the removal rate is high, and there is no secondary pollution. CN105130062A Degradation of anthraquinone dye (such as 2-Methylanthraquinone) wastewater by high temperature and high pressure by wet oxidation. Electrochemical oxidation method uses the free radical generated by electrochemical action to oxidize the ring, scission, and further oxidize to small molecular compounds such as CO2 and H2O.
At present, the research mainly focuses on the improvement of catalytic performance of electrode materials and the improvement of current efficiency and energy consumption, such as CN101508477A and CN102225795A. Photocatalytic oxidation is the treatment of anthraquinone dyes (such as 2-Methylanthraquinone) wastewater by metal-based semiconductor photocatalytic oxidation. At present, the research content mainly involves catalysts and their modification (semiconductor photocatalysts are developing rapidly, such as CN104549404A, CN1415549A) combined with oxidants and other methods. Common low temperature plasma processing techniques include high voltage pulse discharge, glow discharge, sliding arc discharge, and dielectric barrier discharge. CN101254960A utilizes a plasma generated gas to impinge on the treatment of anthraquinone dye (e.g., 2-Methylanthraquinone) wastewater to solve the problem of low processing efficiency. The electron beam decoloring treatment uses 60Co as a radiation source. This method can be combined with chemical methods, biological methods, etc. to reduce the radiation dose and reduce the cost. JPS52113054A uses an electron beam irradiation combined with coagulation technology to treat anthraquinone dyes (such as 2-Methylanthraquinone).