Although cationisation is an effective way to reduce salt consumptioninreactive
coloring,there are still other issues that cannot
be ignored. Under alkaline fixation condition (pH over 10.5), the
reactive dyes can react not only with the hydroxyl groups in cotton
but also with water to form hydrolyzed dyes as well. Undoubtedly,
this competitive process will significantly compromise the coloring
efficiency of cotton with reactive dyes. Moreover, the hydrolyzed
dyes may be weakly attached to cotton by secondary forces and
must be thoroughly washed off at the end of coloring cycle for satisfactory
fastness (Burkinshaw & Katsarelias, 1997; Burkinshaw &
Paraskevas, 2011). As a result, large volumes of wastewater, containing
significant amounts of hydrolyzed dyes and chemicals, have
to be discharged from a typical cotton coloring works (Xue, Li, & He,
2009).