Dual‐mode sorption of nonionic azo dyes by Nylon 6

Abstract

SYNOPSISSorption isotherms of 2,4-&nitroaniline and three 4-amino-azobenzene derivatives ( nonionic dyes with adequate solubility in water) on Nylon 6 (film and fiber) from water were determined at various temperatures. The observed isotherms were curved, not linear. They were very well described in terms of the dual-mode sorption model, Nernst-type partitioning, plus Langmuir sorption. The contribution of the Langmuir sorption to the total dye sorption decreased with increasing temperature. The saturation value for the Langmuir sorption increased with the crystallinity of Nylon 6 film, suggesting that the Langmuir sorption is associated with the crystalline phase. Keywords: sorption isotherms of nonionic azo dyes from water on polyamide Nylon 6, sorption of nonionic azo dyes from aqueous solution by crystalline phase of Nylon 6 and sorption of nonionic azo dyes

Relation between molecular size of non-ionic dyes and their diffusivity in nylon 6 film.

“…Normally, the dissolved species is predominant (15,17), and the actual diffusion coeffi cient (DL(Q) of the adsorbed species is much smaller than that (Dpp) of the dissolved one (15,17). Howev er, the ratio of the concentration (CL) of the adsorbed species to that (Ce) of the dissolved one, CL/Ce in creases in low Cf range [15,16]. These result in the deviation of the experimental points from the calcu lated profiles in the low C/Co range as shown in Fig.…”

“…Each curve fits well to the experimental points except in the range of very small C/Co. The deviation of the experimental points from the curve in this range is explained in terms of the dual-mode sorption of the penetrants by the film (15)(16)(17). Two concurrent sorption mechanisms are operative by the dye sorption by nylon 6 film; a Nernst type partition and a Langmuir type sorption.…”

Effect of Dispersants on the Sorption Isotherm of Nonionic Dyes on Polymers from Water.

“…Recently, however, we have found that the sorption isotherms of purified disperse dyes on various polymers from water in the absence of dispersants are usually curved, convex upward, particularly in the range of low dye concentration Cs in water (7)(8)(9)(10) . The isotherms were well described in terms of the dual-mode sorption model expressed by Eq.l (7)(8)(9)(10).…”

“…The isotherms were well described in terms of the dual-mode sorption model expressed by Eq.l (7)(8)(9)(10). (1) where Cp and CL are the equilibrium concentration of dye on polymer sorbed by Nernst type partitioning and Langmuir sorption, respectively; S is the saturation value for Langmuir sorption and KL is the Langmuir constant.…”

“…Sorption isotherms were measured by means of similar manner as used in previous works (7)(8)(9). The calcula tions were made on a NEC-9801 RA-21 personal com puter equipped with a numerical coprocessor (80387).…”