Use of Fungal Laccases and Peroxidases for Enzymatic Treatment of Wastewater Containing Synthetic Dyes - Green Chemistry for Dyes Removal from Wastewater - page 206

vat, acid, and basic), its hue, and a serial number [18]. For example, an
anthraquinone dye Remazol Brilliant Blue R is also called Reactive Blue 19
and C. I. 61200 (Figure 6.1). For more information, consult Colour Index
International's website. In this chapter, the C. I. generic names, if known,
are used primarily in the text and tables.
6.2.2 ChemicalStructures
As an organic compound, a dye has several common moieties for its func-
tions. There are two critical moieties, namely:
t Chromophore - A functional group or a group of func-
tional groups that is responsible for visible light absorption
and color, typically multiple aromatic rings combined with
alkene, carbonyl (>C=O), azo (-N=N-), and nitro (-NO 2 )
groups that form a long conjugated pi-bond system.
t Auxochrome - A functional group that modiies the ability
of chromophore to absorb light and change the wavelength
and intensity of the color, such as hydroxyl (-OH), amino
(-NH 3 ), and sulfonate (-SO 3 - ) groups. Auxochromes also
make the dye more hydrophilic and water soluble and pro-
vide binding capacity to the dyes onto the textile materials
via hydrogen bonds.
Several common chromophores used in synthetic textile dyes are listed
in Table 6.1. In this chapter, synthetic dyes are mostly classified by their
chromophores. Figures 6.1-6.8 present the chemical structures of the dyes
covered in this chapter. Common names (such as Orange G and Congo
red) used in the reviewed references are shown below the chemical struc-
tures and the C. I. generic names with brackets. Please note that the list
shown in Table 6.1 is not exhaustive and there are several other chemical
classes of dyes, such as diazo, triazo, and formazan dyes. Interested read-
ers should consult with C. I. International, as well as other chapters of this
topic and literature such as Zaharia and Suteu [1].
Some auxochromes such as chlorotriazole and vinyl sulfonyl groups
are vital for fixation of reactive dyes that are commonly used in dyeing of
cotton, flax, wool, and nylon. See Figure 6.6 for a chlorotriazole group in
Reactive Blue 15 and Figures 6.1 and 6.3 for vinyl sulfonyl group precur-
sors in Reactive Blue 19 and Reactive Black 5, respectively. In the case of
cellulosic textiles, such as cotton and flax, these functional groups can be