Electrophoretic mobility of latex spheres in the presence of divalent ions: experiments and modeling

Electrophoretic mobilities (EPM) of negatively charged latex spheres were measured as a function of salt type and salt concentration. The measured values of EPM were analyzed using a standard electrokinetic model that includes double layer relaxation and the Poisson–Boltzmann model of diffuse double layer. Calculated values of EPM were in good agreement with experimental data taken in simple 1:1 (KCl) and 1:2 (Na2SO4) electrolyte solutions without using any fit parameters. For 2:1 electrolytes (CaCl2 and MgCl2), however, the magnitude of EPM calculated by the model was higher than the measured values of EPM at higher electrolyte concentrations. The difference between measured and calculated EPM was reduced by assuming the distance of slipping plane x s = 0.25 nm or by assuming the decrease of the magnitude of surface charge density from −0.07 to −0.025 C/m2. These are probably due to the accumulation of divalent counterions in the vicinity of a particle’s surface

Staining of undyed fabrics when washed with dyed cotton fabrics using alkyl polyglucoside mixtures with anionic surfactant

The increasingly widespread use of non-ionic surfactants as main ingredients in domestic detergent formulations requires an understanding of their performance during washing, not only as separate products but also as binary mixtures with anionic surfactants. In order to attain acceptable levels of biodegradability and toxicity, alkyl polyglucosides (APGs) have appeared on the market. These non-ionic surfactants, obtained from natural substances (saccharides), are 100% biodegradable and have very attractive features for application to washing. They are highly soluble, only slightly sensitive to the presence of electrolytes and rarely affected by water hardness. The aim of our work was to analyze behavior in the staining of undyed cotton fabric with the dye desorbed in the washing of cotton fabric previously dyed and finished with resin and softened, by means of the use of the surfactant APGs with sodium dodecyl benzene sulfonate, separately and in mixtures in different proportions. Likewise, the staining of undyed diacetate, polyamide, polyester, acrylic, cotton and wool fabrics was obtained. The cotton was previously dyed with red, orange and blue direct dyes. The behavior of the discoloration of dyed and finished and unfinished cotton fabric and the staining of undyed fabrics in washing were related to the zeta potentials of the fabrics obtained by the streaming potential method in the presence of the surfactants and their mixtures used After washing, the undyed fabric with the anionic surfactant showed a greater difference in color than non-ionic surfactant and when the concentration of the non-ionic surfactant in the mixture was increased the color difference decreased. The zeta potentials (absolute values) of undyed and dyed and finished cotton fabric in the presence of these surfactants gave the same order values, which increased with the surfactant concentrationPostprint (author’s final draft