Roles of electrostatic interactions in the peroxide systems for bleaching of cotton fiber

Abstract The industrial bleaching of cotton fiber is often carried out in an aqueous solution of hydrogen peroxide (H2O2) with the addition of sodium hydroxide (NaOH) at a boiling temperature. In order to overcome the higher energy consumption problem of the H2O2/NaOH system, activated peroxide systems are proposed by adding so-called bleach activators to the H2O2 solution in which bleach activators can react with H2O2 to generate more kinetically active bleaching species enabling cotton fiber to be bleached at lower temperatures. In previous studies, most researchers focused their attention on the chemical behaviors of bleaching species. In this paper, it was found that the electrostatic interactions between bleaching species and cotton fiber might be played an important role in the peroxide systems for bleaching of cotton fiber. In order to disclose the effects of electrostatic interactions on the bleaching performance, cotton fiber was modified with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC) which changed the negative surface charge of cotton fiber to positive one, and bleached with the H2O2/NaOH system and activated peroxide systems that generated bleaching species with various ionic charges. It was found that the electrostatic attraction between bleaching species and cotton fiber contributed to improving the bleaching performance, but the electrostatic repulsion between bleaching species and cotton fiber undermined the bleaching performance. The addition of a neutral electrolyte (e.g. NaCl) and ionic surfactants to these bleaching systems could give rise to similar charge effect. Hence, the findings in this work provide further understanding that the performance of the peroxide systems for bleaching of cotton fiber depends not only on the chemical activities of the bleaching species but also on the electrostatic interactions between the bleaching species and cotton fiber.