The cellulose ion formed a covalent bond on the reactive
dye, after which the chloride groups of the reactive dye were
released into the solution (Fig. 5). In this dyeing process,
Na2SO4 was added in the first step of dyeing to prevent
dye hydrolysis and increase the physical adsorption between
the dye and fabric. The synthetic reactive dyeing wastewater
also consisted of reactive dye, Na2SO4, and Na2CO3. Therefore,
the hydroxyl groups of chitosan might be attached to
the reactive dye by covalent bonding under caustic pH, as in
the case of cellulose in dyeing processes.
Table 2 shows the effect of the hydroxyl group on chitosan
and cellulose polymers (cotton wool and microcrys-