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Thermodynamic Characterization of the Adsorption Process of Mordant Black 17 Dye onto Polyamide Fabric
Author(s) -
EspinosaJiménez M.,
PadillaWeigand R.,
OntiverosOrtega A.,
PereaCarpio R.
Publication year - 2001
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/1439-2054(20010501)286:5<302::aid-mame302>3.0.co;2-6
Subject(s) - mordant , adsorption , freundlich equation , enthalpy , sorption , thermodynamics , materials science , polyamide , ionic strength , chemistry , polymer chemistry , dyeing , composite material , organic chemistry , aqueous solution , physics
Data are presented on the kinetics and thermodynamics of adsorption of Mordant Black 17 by Polyamide‐6,6 fabric at different temperatures and at an ionic strength constant of 10 –3 m of NaCl in the solutions of the dye. Increased temperature of the system increases the dye content of the fabric in the presence or absence of NaCl in the liquid phase. The presence of NaCl in the liquid phase increases the amount of dye taken up by the fabric. The experimental time‐sorption isotherms are represented by the exponential kinetic equation, M t = M eq (1 – e – kt ), where M t and M eq refer to the amounts of dye taken up by Polyamide‐6,6 at time t and equilibrium, respectively, and k refers to the rate constant. The empirical rate constant increases with increasing temperature of the process in absence of NaCl in the liquid phase. On the other hand, the empirical rate constant decreases with the temperature of the process in the presence of NaCl in the liquid phase. Values of half‐adsorption time at different temperatures are presented. Sorption equilibria of Mordant Black 17 by Polyamide‐6,6 are described by a Freundlich isotherm equation. Changes of enthalpy and entropy related to the process of adsorption of Mordant Black 17 onto Polyamide‐6,6 in the presence of NaCl in the liquid phase are calculated from the Clausius‐Clapeyron equation. Isosteric heats of adsorption are positive, between 30 and 180 kJ/mol. The global change of entropy is positive, between ca. 200 and 650 J/mol· K. The best thermodynamic conditions for dye uptake by Polyamide‐6,6 appear at the highest temperatures, when the standard free energy of adsorption takes the most negative values. From the results, we find that the adsorption of Mordant Black 17 by Polyamide‐6,6 in the temperature interval investigated takes place with establishment of chemical bonds between the OH – negative groups of the dye and the carboxyl groups of the fabric, although physical contributions of an electrostatic or van der Waals nature between the molecules of the dye and the end‐groups of the Polyamide‐6,6 cannot be neglected.