Isolation of natural colorants from Lagerstroemia indica: Kinetic and adsorption studies

Abstract

The color components extracted and isolated from the fruits of Lagerstroemia indica were characterized by NMR, mass, IR and UV/visible spectral techniques. The bio-colorants isolated were found to be quercetin and apigenin. The dyed samples exhibited good colour fastness to washing and perspiration. CIE Lab values have also been evaluated. The rate of dyeing was higher at higher temperature. The thermodynamic parameters were evaluated using Arrhenius plot. The positive value of enthalpy change (ΔH≠) indicated endothermic nature of adsorption, the high negative entropy (ΔS ≠) revealed that the color components adsorb more orderly on silk and the positive value of free energy (ΔG≠) validated the strong affinity between adsorbent and adsorbate. Adsorption study was carried out based on the model proposed by Langmuir, Freundlich, Tempkin and Pyzhev isotherm to account for the observed results. The Freundlich isotherm was found to fit best with high regression coefficient. The colorants obtained from Lagerstroemia indica fruit could form a potential source as a dye for textile dyeing. © 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.