An adsorption study of alum-morin dyeing onto silk yarn
Silk yam 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 (E-a) of 45.26 KJ/mol. The value of the enthalpy or activation (Delta H-#) for alum-morin dyeing on silk at pH 4.0 was -31.29 kJ/mol. Also, the free energy (Delta G degrees) and entropy changes (Delta S degrees) 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.