Adsorption of anionic surface active substances (SAS) on charged membranes

We investigated the adsorption of aqueous solutions of sodium dodecylsulphate (NaDS) on poly-amide membranes of different composition. Experimental membranes PA-100((+)) were a mixture of polyphenyl-phthlamide and copolymer of acrylonitrile with dimethyl diallyl ammonium chloride (60:40) and PA-100((-)). These were based on the product of copolycondensation of sodium salt of 4,4'-diamindiphenilamine-2-sulphonic acid (8 mol.%) and m-phenylenediamine with isophthaloyl chloride with pore sizes 5.7-9.0 rim and a small surface charge. Also used was a PA-10 membrane of poly-phenileisophthalamide with a pore radius of 2.9 to 5.8 nm. It was shown that maximum adsorption on the PA-10 was determined mainly by the electrostatic interaction of NaDS with the PA-10 surface. Analysis of the adsorption mechanism on PA-100((+)) and PA-100((-)) showed that the adsorption layer structure determining the characteristics of the membranes for these membranes was effectively different, which was confirmed by the data on desorption of NaDS by water from the membrane surface.