The sorption of ions by polyamides

Abstract

S~O P S i SAn analysis is given of the principal thermodynamic factors that influence the distribution of an ion between a macroscopically homogeneous polymer phase and a second homogeneous phase and a general method is proposed for the computation of the equilibrium ion sorptions in well-defined model systems. Particular attention is paid to the sorption of ions by polymers containing ionizable groups and the method is used to clarify some of the current problems in the theoretical explanation of the mechanism of sorption of acid dye anions by polyamide fiben. The method is applicable in principle to any dyeing system in which the fiber phase may be regarded a t equilibrium as a macroscopically homogeneous, equipotential volume.

The graphical evaluation of ionic dye sorption isotherms using dimensionless groups

“…(2) for the unknown parameter A, followed by the use of eq. (1) to calculate the Ct. This procedure must be followed for each change in the solution concentrations Cf, or in any of the parameters of eqs.…”

Investigation of the Polyamide 6,6 dyeing process with Acid Blue 45 dye. Part I. Thermodynamics of Acid Blue 45 adsorption

“…The rst is diffusion of the dye molecules to the bre surface; then its actual adsorption onto the surface (driven by the entropy changes), followed by diffusion into the bre (also determined by entropy and enthalpy changes); and nally, the formation of bonds between the absorbed and adsorbed dye and the polymer molecules. McGregor and Harris [17] have developed a theoretical model for the adsorption of a dye to a polyamide. In a simpli ed model, they considered surface adsorption of the dye to be unimportant and assumed a homogeneous structure of the polyamide phase.…”

“…This will be further discussed in Part II [16]. In McGregor and Harris' [17] derivation of the adsorption equation, which was discussed above, the surface adsorption was assumed as unimportant, and the absorption process was considered only without any speci c interactions between the dye anions and charged amino groups of the bre. The charged groups were, however, taken into account as a necessary condition for neutrality, which is included in the¸parameter [equation (1)].…”

“…Langmuir type) and subgroup 2, and can occur for adsorption from molecularly dispersed as well as aggregated solutes, probably with a at orientation of the molecules [17,18]. According to the authors [17,18], this type of isotherm occurs when the activation energy terms (of the solute, solution, and any other component of the solution) are independent of the concentration. In bre systems giving L-type isotherms, it can be assumed that the sorption is initiated by absorption (penetration) of the molecules into the bre structure [20].…”

“…Anyway, despite the possible mechanism of the observed slight pH increase, it must be caused by the dye adsorption. It is should be recalled that the pH of these systems is much smaller than the pH of the abrupt increase in the dye sorption (pH > 10) predicted by McGregor and Harris' model [17]. From the plateau in the sorption isotherm one can evaluate the speci c surface area of the polyamide fabric.…”