An adsorption study of alum-morin dyeing onto silk yarn

Abstract

Silk yarn was dyed with morin (2′,3,4′,5,7-pentahydroxyflavone) by using alum as mordant. In order to optimize the process, three methods of dyeing involving: pre-mordanting, simultaneous mordanting, and post-mordanting were assessed and compared with a mordant-free process. The adsorption of alum-morin dye onto silk fibers indicated that the adsorption capacities were significantly affected by pH, the initial dye concentration, and temperature. The initial dye adsorption rates of alum-morin dye on silk before equilibrium was reached increased with higher dyeing temperatures. The pseudo second-order kinetic model was indicated for alum-morin dyeing (simultaneous mordanting) of silk at pH 4.0 with an activation energy (Ea) of 45.26 kJ/mol. The value of the enthalpy of activation (ΔH#) for alum-morin dyeing on silk at pH 4.0 was −31.29 kJ/mol. Also, the free energy (ΔGo) and entropy changes (ΔSo) for alum-morin dyeing on silk were −17.73 kJ/mol and −45.7 J/molK, respectively, consistent with a spontaneous and exothermic adsorption process.