Sorption of Zinc Ions by a Nonwoven Polypropylene Material Modified with Poly(acrylic acid) Grafted to the Fiber Surface: The Role of Grafting Density and Hydrogen Bonds

A microfiber carboxylic cationite is prepared via the photoinduced polymerization of acrylic acid on the surface of nonwoven polypropylene material. Changes in the amount of the graft polymer (grafting density) and in the strength of hydrogen bonds between its carboxyl groups, depending on the polymerization time, are investigated by attenuated total internal reflectance FTIR spectroscopy. The sorption properties of the obtained ionite in the acidic (COOH) and salt (COONa) forms with respect to Zn2+ ions at various grafting densities are studied. The sorption capacity of the investigated cationite in its salt form is higher than that in the acidic form, and this difference increases quickly with the grafting density. The data of IR spectroscopy showed that this behavior is caused by the formation of stronger hydrogen bonds between COOH groups of the grafted polyacrylic acid, complicating their ionization and, thus, preventing the ion exchange.