3.2.1. Elution test of dye-adsorbed chitosan under acidic
conditions
Table 3 shows that water could not elute the SRDW from
chitosan polymer, whereas NaOH could elute only 32%. In
addition, the synthetic reactive dye had many sulfate anionic
groups in the dye polymer, which could attach to
many amine groups on the chitosan polymer, and electrostatic
interaction occurred. However, the amine groups are
hydrogen-bonded to the sulfate anions and the water molecules
form infinite (H2O)n chains of dye and, through the
sulfate anions, link the amine group in the three-dimensional hydrogen bond network [12]. Therefore, the interaction between
sulfate anions and amine groups difficulty in elution
to 100% using 1 M NaOH. In addition, this result also con-
firmed that the adsorption mechanism was chemical adsorption.