Solubility of Two Disperse Dyes Derived from N‐Alkyl and N‐Carboxylic Acid Naphthalimides in the Presence of Gemini Cationic Surfactants

Abstract

AbstractThe solubility of naphthalimide‐based monoazo dyes containing N‐ethyl and N‐ethanoic acid groups was investigated in the presence of a conventional monomeric counterpart (DTAB) and two cationic gemini surfactants (12‐4‐12 or 14‐4‐14) individually. The effective parameters on dye solubility such as temperature, time and concentration of surfactants were investigated by UV–Visible spectrophotometry. The results demonstrate that the solubility of both dyes was considerably increased at concentrations above the surfactant CMC. The wavelength for the maximum absorbance of dyes in the aqueous solution shifts toward longer wavelengths with changes in the concentration of the cationic surfactants. A kinetic study of solubilization of dyes in cationic surfactants solution showed that the rate of solubilization follows the pseudo‐first‐order reactions. Rates of solubilization were in the range of 0.5 × 10−3 to 6.8 × 10−3 min−1 for both dyes. The disperse dye containing a carboxylic acid group (dye 2) has a higher solubility rate than the dye containing an alkyl group (dye 1). The type of surfactant has a very low effect on adsorption of dye 1 onto the polyester fibers, whereas changing the surfactant type from DTAB to 12‐4‐12 or 14‐4‐14 causes adsorption of dye 2 on polyester to decrease.