Interactions in the system: Clay‐detergent‐cellulose

Abstract

AbstractThe McBain equation describing detergency was used to study the process cellulose·clay+detergent= cellulose·detergent+clay·detergent, by taking thoroughly purified cotton, montmorillonite swelling clay, and n−C12H25O (CH2CH2O)−14H as well as other nonionic and anionic detergents. The three binary equilibria which add up to this ternary system were also studied.X‐ray diffraction showed that monionic detergents sorbed by the clay were intercalated between adjacent, 9.5 Å thick lattice layers of clay with their chains parallel to these layers, in sheets one or two molecules thick. The process was accompanied by dehydration and proceeded down to low equilibrium detergent concentrations. The deflocculation of sodium montmorillonite suspensions by polyoxyethylated compounds was shown by an increase in turbidity and decreases in viscosity and sedimentation volume. Cellulose sorbed C12H25O (CH2CH2O)14H reversibly. Its uptake was considerably less than that of clay on a weight basis but was comparable on an area basis.Kaolinite and calcium montmorillonite picked up by cellulose from aqueous suspensions were gradually removed by washing with water, following first‐order kinetics.Of the sodium montmorillonite picked up, 0.13±0.01% could not be removed by washing with water. This level of tenaciously retained clay was independent of clay concentration, rate of stirring, and temperature. The ash of fabric treated with sodium montmorillonite was a shrunken replica of the fabric, preserving microscopic details faithfully. This and comparison of the specific surface areas of cotton and sodium montmorillonite indicate that cotton was completely coated with clay to an average depth of three to four lattice layers. The reason for this thickness is that the primary particles in sodium montmorillonite dispersions are packets of three to four lattice layers.Anionic and cationic detergents removed little or none of the 0.13% sodium montmorillonite. Polyoxyethylated and polyoxypropylated compounds removed part but always left behind at least 0.04%. This is the amount of clay required to cover the cellulose surface completely with a sheet of single, nonoverlapping lattice layers. However, when brought into contact in the presence of nonionic detergents, cellulose retained no sodium montmorillonite at all.