Effects of added metal ions on the interaction of chitin and partially deacetylated chitin with an azo dye carrying hydroxyl groups

Abstract

The binding of chrome violet, which is a monoazo dye and involves two hydroxyl groups in the o and o′ positions to an azo group, to chintin and partially decetylated chitin, was examined in the presence of metal ions. Zn²⁺ and Cu²⁺ ions do not perceptively influence the binding affinity of chrome voilet to chitin. In contrast, Co²⁺ ion enhances the binding and Ni²⁺ ion suppresses it. In the lower free dye concentrations the dye uptake by partially deceteylated chitin was tremendously enhanced by adding. Co²⁺ ion in the buffer solution of pH 5. The dye uptake by the polymer was considerably increased by the addition of Cu²⁺ ion at pH 5 and became much larger at pH 6. The amount corresponded to that in the presence of Co²⁺ ion. To investigate further the action of added metal ions, a cobalt‐ or a chrome–complex dye was prepared, and the binding properties for the polymers were compared with those of chrome violet in the presence of Co²⁺ and Cu²⁺ ions. Some possible mechanisms for the enhancement of chrome violet binding by the addition of Co²⁺ and Cu²⁺ ions are described. © 1995 John Wiley & Sons, Inc.