Single and Hybrid Applications of Ultrasound for Decolorization and Degradation of Textile Dye Residuals in Water - Green Chemistry for Dyes Removal from Wastewater - page 264

Table 7.1(b) ( Cont .)

Classification by
application

Applied fiber

Disperse polyester, acetate

Basic wool, silk, acrylic/modified acrylic

Mordant wool, wool blends, silk, cotton, modified cellulose

Pigment cellulose

Reactive cellulose, cotton, flax, wool, nylon fibers

Sulfur cotton

Vat cellulose, cotton, wool

Table 7.2 The auxiliary chemicals and their functions in textile dyeing
operations.

Auxiliaries used Composition Function

Salts Sodium chloride, sodium

sulfate

Neutralize electrical
charge on fiber; retard

Acids Acetic, sulfuric pH control

Bases Sodium hydroxide,

sodium carbonate

pH control

Buffers Phosphate pH control

Sequestering agents EDTA Complex, retard

Dispersers/surface
active reagents

Anionic, cationic,
non-ionic

Regulate, soften

Oxidizing agents Hydrogen peroxide,

sodium nitrite

Insolubilize

Reducing agents Sodium hydrosulfite,

sodium sulfide

Solubilize, remove unfixed
dyes

Carriers Phenyl phenols,

chlorinated benzenes

Enhance absorption

operations due to the stability of the azo structure. On the other hand,
the azo bond is disintegrated both anaerobically and by hydrolysis to pro-
duce carcinogenic amines [13-18]. Additionally, the presence of one or
more sulfonic groups in nearly all azo dye structures makes them highly
polar and water soluble and thus very difficult to separate by conventional
physical-chemical operations, as well [19].
Current experience on the treatment of dyeing mill wastewater is
focused on processes such as adsorption, coagulation, precipitation and