Chelating agents are employed in several different applications in the textile industry. In the scouring stages, chelating agents are used in all cleansing and preparation steps of textile finishing. They function to increase cleaning effectiveness and remove metal ions which may be harmful in subsequent bleaching and dyeing operations.
In the bleaching process, heavy metal ions (Cu2+, Mn2+ and Fe3+) cause the catalytic degradation of hydrogen peroxide and other peroxygen bleaching compounds. Besides the loss of bleaching compound, the metal induced catalytic degradation can cause fiber tenderization.
The successful dyeing process also depends on chelation. Dyestuffs are sensitive to divalent and trivalent metal ions. Precipitates may form and cause variation in dye shade because of the presence of calcium, magnesium, iron and copper. Since the dye itself may contain a metal complex, extreme care must be taken in selecting the right chelator.