Physical Chemistry of Dyeing of Cellulosic Fibers with Reactive Dyes

Abstract

The effect of different electrolytes on the sorption of the hydrolyzed form of four different reactive dyes has been investigated. The electrolytes studied were sodium, ammonium, Jithium, and magnesium chlorides, and ammonium sulfate, which differ widely in their ability to increase the sorption of hydrolyzed reactive dyes by cellulose. Their relative efficiencies were in the order: ammonium chloride > ammonium sulfate > sodium chloride > lithium chloride ~ magnesium chloride. The effect of the electrolytes has been discussed in terms of partial screening of the surface charge on cellulose by the crowding of the cations at the cellulose-water interface, pH of the bath, and the ability to modify the structure of water. The ability of the electrolytes to modify the pH of the solution plays a dominant role in sorption increase at lower con centrations of electrolytes, whereas at higher concentrations the ability of the electrolytes to modify the cellulose-water interface plays a decisive role.

Influence of water hardness on acid dyeing with silk

“…At low concentrations, screening effect plays an important role, calcium ions could reduce |] | to a greater extent. However, when the concentration of cation is high, the ability to modify the fibre-water interface plays a decisive role [18]. Since the ability of calcium ion to modify the fibre-water interface is smaller than that of sodium ion, as a result, the rate of the decrease in |] | under the influence of calcium ion became less pronounced with higher concentrations.…”

“…With further increase of electrolyte concentration, over 200 ppm, the influence of dye exhaustion and fixation caused by calcium ions become less, while in the case of sodium ions, the dye exhaustion and fixation increase in a linear manner. When the concentration of electrolytes is high, the ability of the electrolyte to modify the fibre-water interface [18] and to disrupt the water structure of hydrated water around the hydrophobic parts of dye molecules [23] will play a decisive role. It can therefore be postulated that because the abilities of calcium ions to modify fibre-water interface and to disrupt the structure of hydrated water is smaller than that of sodium ions, their promoting effect on exhaustion and fixation becomes smaller.…”

Effect of Counterions and Ureas on Adsorption of Direct Dye on Cellulose

“…Madan and Shrivastava [7] and Sivaraja Iyer and Subramanian [ 13] reported that, in addition to the suppression of surface potentials that help the dye adsorption process on cellulose, cations influence the dye adsorption by disrupting the structure of water bound to the surface of cellulose. In this report, we first indicate that adsorption of direct dye on cellulose in the presence of different kinds of counterions increases in the order Cs+ > K+ > Na+.…”

“…In addition to the fact mentioned above for counterions on dye adsorption, the cation for electrolyte may influence the dye adsorption by the well known effect of electrolytes suppressing surface potential, which helps the dye adsorption process [7,13]. Madan [7] and Sivaraja Iyer [!3] also reported that cations for electrolytes influenced the dye adsorption by disrupting the structure of water bound to the surface of cellulose.…”

“…Madan [7] and Sivaraja Iyer [!3] also reported that cations for electrolytes influenced the dye adsorption by disrupting the structure of water bound to the surface of cellulose. However, one may think that the cations as water structure breakers, which perturb the hydrogen bond of the intermolecular water-water interactions, have no ability to disrupt the structure of water bound tightly to the surface of cellulose, since the strength of the hydrogen bond between water and the hydroxyl group of cellulose, which is a polysaccharide derivative, is considered to be stronger than that between water and water [9].…”