Dyeing Studies with Eucalyptus, Quercetin, Rutin, and Tannin: A Research on Effect of Ferrous Sulfate Mordant

Natural dyes from Eucalyptus leaf extract, quercetin, rutin, and tannin were applied to silk fabric by pad-batch and pad-dry techniques under different conditions. Ferrous sulfate was used as a mordant. The dyeing properties were evaluated by measuring K/S and CIELAB values. In addition, the different fastness properties were evaluated. The effect of dyes at different concentration levels with respect to their colour strength was also studied. 1. Introduction Natural dyes are comprised of dyes and pigments that are obtained from various parts of plants including roots, bark, leaves, flowers, and fruit [1]. The major applications are coloring of food, leather, wood, and natural fibers like wool, silk, cotton, and flax. Natural dyes may have a wide range of shades. Dyeing with natural dyes, however, normally requires the use of mordants, which are metallic salts of aluminum, iron, chromium, and copper, among others, to ensure a reasonable color fastness to sunlight and washing [2]. The metal ions of these mordants can act as electron acceptors for electron donors to form coordination bonds with the dye molecules, making them insoluble in water [3]. Lately, there has been increasing interest in natural dyes, as the public is becoming more aware of the ecological and environmental problems related to the use of synthetic dyes. The use of natural dyes cuts down significantly on the amount of toxic effluent resulting from synthetic dye processes. Natural dyes have also been used for printing and dye-sensitized solar cells [4–7]. Alongside their aesthetic qualities, natural dyes may offer other benefits, being antibacterial, deodorizing, and UV protective [8–14]. The use of natural dyes in textile applications is growing rapidly, reflecting the strict environmental standards being established in many countries, and the concern about the health hazards associated with synthetic dyes, for example, the recent ban on the use of azo dyes by the European Union, has also increased the scope for the use of natural dyes [15]. Eucalyptus is one of the most important sources of natural dye, yielding several yellowish-brown colorant. Eucalyptus has ample natural tannins and polyphenols ranging from 10% to 12% [16]. The major coloring component of Eucalyptus bark is quercetin, which is also an antioxidant. It has been used as a food dye with strong antioxidant properties [17]. Eucalyptus leaves contain up to 11% of the major components of tannin (gallic acid and ellagic acid) with flavonoids (quercetin, rutin, etc.) as minor substances [18–20]. Tannins and flavonoids are