An adsorption and kinetic study of lac dyeing on silk
Introduction
Lac dye is a natural reddish dyestuff extracted from stick lac which is a secretion of the insect Coccus laccae (Laccifer lacca Kerr). The insect C. laccae is often found in South and Southeast Asia, especially in Thailand and India. In Thailand, the lac insect grows most commonly on the Rain tree, Samanea saman (Jacq.) Merr. (Pithecolobium saman, Mimosaceae) [1]. Lac dye, which is the soluble part of stick lac, is composed mainly of two major anthraquinone-based components: laccaic acids A and B [2], [3], [4], [5], [6], [7], [8]; the minor components, laccaic acids C, D and E, have also been isolated [9], [10] (Fig. 1). All have an anthraquinone moiety with dicarboxylic acid groups, except for laccaic acid D which is a monocarboxylic acid. The quantities of these laccaic acid components depend on the locality and the season. Erythrolaccin (Fig. 1) is another component of the lac dye [2], but this can be removed by ethanol extraction.
Lac dye is used extensively as a natural food additive [7], [11], and in cosmetics [7], as well as a colourant for silk and cotton dyeing [1]. In the north and the northeast of Thailand, it is used as a natural red dyestuff for cotton and silk dyeing but the fastness properties and reproducibility to give consistency in production are still problems to be solved. As part of the approach to tackle these problems, fundamental physical studies on the dyeing process are important.
The thermodynamics of adsorption of laccaic acids on silk has been studied [12], but without pH control and the results indicated that the adsorption isotherm of silk dyeing with laccaic acids, from which the erythrolaccin had been removed, was of the Langmuir type. Also values for the heat and entropy of dyeing were reported [12]. However, there have not been any complementary studies on the kinetics of the dyeing process and such studies are now reported in this paper. The adsorption rates were measured and determined quantitatively in relation to dye solution pH values, contact time, initial dye concentration, and material to liquor ratio (MLR). The Langmuir and Freundlich equations were used to fit the equilibria.
Section snippets
Silk yarn
The silk yarn used was purchased from villagers living in Nakhon Ratchasima, Thailand. To remove the sericin gum, the silk yarn (1 kg) was added to boiling water (5 L) to which soap flakes had been added (ca 100 g), sodium silicate (10 g), sodium carbonate (50 g) and 40% hydrogen peroxide (100 mL). The mixture was then boiled for 2 h. The silk was then removed, washed with water, squeezed to remove excess liquor and air dried. Finally, it was treated with 1 M HCl (ca 3 L) at room temperature for 30 min
Optimal conditions for lac dye onto silk
In order to investigate the adsorption of lac dye onto silk, the experiment parameters including pH, material to liquor ratio (MLR), contact time, initial dye concentration and temperature were determined to find the optimal conditions for adsorption.
Conclusions
The adsorption isotherm and kinetics of lac dyeing were studied. The following results were obtained:
- 1.
Adsorption data were modeled by using the Freundlich and Langmuir adsorption isotherms. A high correlation coefficient (R2 > 0.99) with both isotherms was obtained.
- 2.
Initially, the rate of adsorption of lac dye onto silk yarn was very fast. This was then followed by a slower rate, and gradually approached a plateau.
- 3.
Before equilibrium was reached, an increase in temperature lead to an increase in the
Acknowledgements
We gratefully acknowledge support from the Ministry of University Affairs, Thai Government for Montra Chairat. We also thank Suranaree University of Technology, Walailak University, and the University of Wollongong for support.
References (24)
- et al.
The constitution of laccaic acid B*
Tetrahedron Letters
(1967) - et al.
Separation of lac dye components by high-speed counter-current chromatography
Journal of Chromatography A
(1998) - et al.
Desoxyerythrolaccin and laccaic acid D*
Tetrahedron Letters
(1968) - et al.
Thermodynamics of adsorption of laccaic acid on silk
Dyes and Pigments
(2002) - et al.
Equilibrium and kinetic modeling of adsorption of reactive dye on cross-linked chitosan beads
Journal of Hazardous Materials
(2002) - et al.
Adsorption behaviour of reactive dye in aqueous solution on chemical cross-linked chitosan beads
Chemosphere
(2003) - et al.
Adsorption of anionic dyes in acid solutions using chemically cross-linked chitosan beads
Dyes and Pigments
(2004) - et al.
Orange peel as an adsorbent in the removal of Acid violet 17 (acid dye) from aqueous solutions
Waste Management
(2001) - et al.
Utilization of industrial waste products as adsorbents for the removal of dyes
Journal of Hazardous Materials
(2003) - et al.
Adsorption kinetics of methyl violet onto perlite
Chemosphere
(2003)
Kinetic modeling of liquid-phase adsorption of reactive dyes and metal ions on chitosan
Water Research
Erythrolaccin
Tetrahedron Letters
Cited by (155)
Natural dyes and pigments as a source of medicine
2023, Renewable Dyes and Pigments