Compensation for Hydrolysis in the Reuse of Reactive Dyes

Abstract

In conventional exhaust processes for applying reactive dyes, the alkali accelerates dye hydrolysis, restricting subsequent reuse. Step-up and chemical build-up can complicate accurate color duplication with reused dyes as well. A two-bath method of first applying the dye from a salt and dye bath followed by treatment in a separate alkali bath eliminates the possibility of alkali-induced hydrolysis, step-up, and chemical build-up effects. In this study, four reactive dyes differing in reactive group and dyeing temperatures are applied to cotton poplin fabric from original and reused dyebaths by one- and two-bath application methods, and the percent fixation of adsorbed dyes and the K/S values are determined. Dye hydrolysis and step-up and wash-off effects that occur in the one-bath method interfere with reuse. These complications are eliminated when the reactive dyes are reused by the two-bath method.

Effect of disperse dye structure on dye sorption onto PLA fiber

“…1 were built using the Visualizer module of MS Modeling 3.0. These disperse dyes were selected for this study because data are available in the literature for their percentage sorption on PLA fiber [1,5,6].…”

“…A molecular dynamics (MD) simulation was then performed, using a constant volume/constant temperature ensemble at 383 K. This temperature was selected since experimental data for their percentage sorption on PLA at 100-110 • C are available in Refs. [1,5,6]. The MD simulation was performed for 100,000 steps with a time step of 10 −15 s and with an equilibration time of 400 × 10 −12 s. This length of time was necessary for the potential energy of the system to stabilize.…”

“…The percentage sorption data were obtained from the literature and are shown in Fig. 1 [1,5,6]. A linear regression was performed for the percentage sorption of the dyes against the U dye-PLA values because increasing percentage sorption onto PLA was expected to correspond to more negative interaction energy between the dye and PLA.…”

“…The commercial PLA fabric was a double knit fabric with a weight of 0.16 kg/m 2 and was made of 90 denier filament yarn and 25 Ne staple fiber yarn. The PLA fabric was washed before dyeing according to AATCC Standard Test Method 124, and it was dyed under the same conditions used by Scheyer and Chiweshe, which were an initial dye bath concentration of 2% owf, a 50:1 liquor ratio, pH 5, and 100 • C dyeing temperature [5]. PLA fiber with a fineness of 12.6 denier was extruded, and the fiber was dyed using an initial dye bath concentration of 3% owf, a 100:1 liquor ratio, pH 5, and 100 • C dyeing temperature.…”

“…PLA fiber is most commonly dyed with disperse dyes. One major concern with PLA is that only a limited number of disperse dyes have been found to have good sorption on PLA at the appropriate dyeing temperature [1][2][3][4][5][6][7]. PLA filaments with higher melting points have yielded greater dye sorption in the cross section of the filaments than have PLA filaments with lower melting points [8].…”