New Erbium(ΙΙΙ) Complexes as Mordants for Natural Dyeing of Silk

This research aims to develop new mordants and a wide range of colors for natural dyeing of silk. For this purpose, two new erbium(ΙΙΙ) complexes, [Er(AO)(H2O)7](OAc)3 and [Er(AMH)(H2O)6](OAc)3 (AO = acridine orange, AMH = azomethine-H, and OAc = acetate anion), were synthesized, characterized, and used as the mordant for the natural dyeing of silk yarns with green walnut husk extract. The mordanting method and the effective dyeing parameters, including the quantity of the dye, pH, and temperature of the dyeing bath, mordant concentration, and dyeing time, were optimized. The colorimetric properties (L*, a*, b* and K/S) and color fastness characteristics (light and washing) of the dyed samples were also investigated. The mordanted silk yarns with the synthesized erbium(ΙΙΙ) complexes were compared to the unmordanted dyed samples, as well as the mordanted dyed samples only with the pure salts, including starting erbium salt (erbium(ΙΙΙ) acetate), stannous chloride, and aluminum potassium sulfate. The results indicated that the dyeing of silk in the presence of [Er(AO)(H2O)7](OAc)3 as the mordant provides the most eminent color contrast, whereas the treated silk with [Er(AMH)(H2O)6](OAc)3 exhibits the most color strength value (K/S). Furthermore, all mordanted and unmordanted samples exhibited proper color fastness characteristics.