Thermodynamics Study of Natural Indigo Adsorption on Silk Yarn
Paisan Kongkachuichay, Aroonsiri Shitangkoon, and Sakowrath Hirunkitmonkon* Author for corresponding; e-mail address: fengpsk@ku.ac.th
Volume: Vol.37 No.2 (MAY 2010)
Short Communication
DOI:
Received: 14 January 2010, Revised: -, Accepted: 9 March 2010, Published: -
Citation: Kongkachuichay P., Shitangkoon A. and Hirunkitmonkon S., Thermodynamics Study of Natural Indigo Adsorption on Silk Yarn, Chiang Mai Journal of Science, 2010; 37(2): 363-367.
Abstract
Leaves of Indigofera tinctoria were fermented in water. During fermentation, indican in leaves decomposed completely to indoxyl and was consecutively oxidized to indigo that finally precipitated from the fermented solution. The hybrid-race silk yarn was then dyed till equilibrium with obtained indigo reduced by Na2S2O4 under alkaline condition and thermodynamics of dyeing process was investigated. The obtained adsorption isotherm was classified as a Langmuir type. The apparent diffusion coefficients at 33, 40 and 50oC are 1.23x10-12, 8.26x10-13 and 4.26x10-13 m2s-1, respectively. The heat of adsorption and the change of entropy are -9.43 kcalmol-1 and 0.023 kcalmol-1 K-1, respectively. In addition, the saturated dye uptake was found to be decreased when the dyeing temperature was increased. The obtained results are useful for designing appropriate dyeing equipment and conditions for dyeing silk with natural indigo.