Effects of Added Metal Ions on the Interaction of Wool Keratin Derivatives and an Azo Dye Carrying Hydroxyl Groups

Abstract

The extent of binding of chrome violet, which is a monoazo dye involving two hydroxyl groups in the o and o' positions to an azo group, by wool keratin derivatives such as S-carboxymethylated, S-cyanoethylated, and regenerated keratin derivatives is markedly enhanced in the presence of Co2+ ion. The amount of binding in the presence of 1 times 10-4 mol/I of Co2+ ion increases by a factor of 12∼20 compared to that in the absence of the metal ion. Cu2+, Ni2+, and Zn2+ ions do not perceptibly influence the binding affinity of the dye. Al3+ ion, in contrast, suppresses the binding. To further investigate the action of added metal ions, we prepared a cobalt-complex dye and compared its binding property for the polymers with that of chrome violet in the presence of metal ions. We also measured the binding of the metal ions by the polymers. Co2+ ion did not exhibit remarkable binding affinity toward the polymers. Some possible mechanisms for enhancing chrome violet binding by the addition of Co2+ ion are described.