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Biofilm and Granular Sludge Bioreactors for Textile Wastewater Treatment
Published in Y.V. Nancharaiah, Vayalam P. Venugopalan, Microbial Biofilms in Bioremediation and Wastewater Treatment, 2019
G. Kiran Kumar Reddy, Y.V. Nancharaiah
Dyes are classified based on their origin, chemical/physical properties and application type (Bafana et al. 2011, Wesenberg et al. 2003). Based on chemical composition, dyes are classified into azo, nitro, nitroso, diarylmethane, triarylmethane, xanthene, anthraquinoid, acridine, cyanine, quinone-imine, pthalocyanine, and thiazole dyes. Based on the application type, dyes are classified as acid, azoic, basic, direct, disperse, mordant, reactive, sulphur and vat dyes. The colour of the dye depends on absorption of specific wavelength of visible light, which in turn depends on the chemical structure of the dye molecules. The chromophore groups such as azo, anthraquinone, methine, nitro, arylmethane and carbonyl are responsible for imparting colour to dye molecules. The auxochrome groups such as amine, carboxyl, sulfonate and hydroxyl groups are responsible for deepening the colour intensity. The auxochrome groups are often bonded to the aromatic or heterocyclic rings of dye molecules.
Dyeing and Recent Developments
Published in Asis Patnaik, Sweta Patnaik, Fibres to Smart Textiles, 2019
Prithwiraj Mal, Debojyoti Ganguly
Colours can be added to textiles either using dye or pigments. Pigments are those colouring materials that are insoluble in water and do not possess attraction towards any fibres. They are comparatively bigger in size and adhere to the surface of textiles by binders. Dyes are water-soluble colouring materials and contain two portions – ‘chromophores’ or colour bearing groups and ‘auxochrome’ or colour helping groups (Gohl and Vilensky 2005). The chromophore decides the colour of the dye molecule, whereas auxochrome intensifies the hue of the colour, fastness property, solubility, etc. Certain dyes are attracted to certain fibres. They are absorbed by the fibres and can be fixed either by chemical or physical bonds (ionic bond, hydrogen bond and van der Waals forces of attraction) with the polymers. The affinity of different dyes towards different fibres and the type of dye–fibre bonds are shown in Table 9.1.
Ultraviolet–Visible Absorption Spectroscopy: Link with Fluorescence
Published in Ali Pourhashemi, Sankar Chandra Deka, A. K. Haghi, Research Methods and Applications in Chemical and Biological Engineering, 2019
Francisco Torrens, Gloria Castellano
Effect of substituents. Auxochrome: functional group that does not absorb in UV region but presents effect of shifting chromophore peaks to longer λ (red shift) and increasing their intensities (hyperchromic). It presents at least a pair of n electrons capable of interacting with ring π electrons. Table 4.5 shows that −OH and −NH2 present an auxochromic effect on chromophore benzene, particularly compared to peak B.
Coagulation/flocculation process for textile mill effluent treatment: experimental and numerical perspectives
Published in International Journal of Sustainable Engineering, 2021
Ahmed Karam, Emad S. Bakhoum, Khaled Zaher
Water pollution is one of the main causes of public health deterioration. A proper strategy has to be applied to diminish water pollution and optimise the use of recycled water. The textile industry is one of the greatest substantial pollution sources. Moreover, it is very voracious to consume fresh water during its production processes (Ghaly et al. 2014). In general, textile wastewaters contain dissolved organic and inorganic ingredients, such as dyes, heavy metals, detergents, starch etc. It can be characterised by elevated chemical oxygen demand (COD), turbidity, temperature, pH and robust colour (Holkar et al. 2016; Yaseen and Scholz 2019). The colour of the discharged textile effluents is mainly owing to the use of dyes which primarily have complex aromatic molecular structure (Carmen and Daniela 2012). Dyes are usually organic and non-biodegradable. It mainly consists of a group of atoms called ‘Chromophore’ responsible for their colour in addition to donating substituent called ‘Auxochrome’ which improves the colour of chromophore (Dos Santos, Cervantes, and van Lier 2007; Ghanbari and Moradi 2016). The most common chromophores are carbonyl (–C = O), azo (–N = N–) and nitro (–NO2) groups. The dye molecules can be strongly fixed by forming covalent bonds that caused by chemical reactions between substitutes on the dye molecules and the fibres (Carmen and Daniela 2012). Dyes in water are frequently toxic and has a significant influence on causing carcinogenicity to the marine organisms and humans (Lellis et al. 2019). On the other side, marine’s life is significantly affected by the increase of organic and inorganic substances as well as suspended solids accompanying the discharged water. They can prevent natural light from penetrating the water which catalyse the occurrence of the eutrophication process (Lellis et al. 2019; Holkar et al. 2016). All of these detrimental characteristics donate to the primacy of textile wastewater treatment before discharging into the environment (Carmen and Daniela 2012). There are several effective methods applied for treating real textile wastewater such as, nanofiltration (Kurt et al. 2012; Riera-Torres, Gutiérrez-Bouzán, and Crespi 2010), ultrafiltration (Alventosa-deLara et al. 2012), electrochemical processes (Chatzisymeon et al. 2006), electrocoagulation (Merzouk et al. 2009), ozonation (Fatimah and Wiharto 2017), reverse osmosis (Kurt et al. 2012), adsorption (Karam, Zaher, and Mahmoud 2020), photocatalysis (Noman et al. 2020) and advanced oxidation processes (Patel and Vashi 2015). All of these methods are either difficult to operate or periodic maintenance (Ghaly et al. 2014). The conventional biological treatment is common used for textile wastewater treatment attributable to its great ability to remove dissolved matters from effluents (Yaseen and Scholz 2019; Elawwad, Karam, and Zaher 2017). Nevertheless, it is not a sufficiently effective method for removing colour due to the poor biodegradation of some types of dyes (Rai et al. 2005).