Citric acid-modified acrylic micro and nanofibers for removal of heavy metal ions from aqueous media

The present work describes a new modification process for producing chelating fibers for removal of heavy metal ions from aqueous solutions. Commercial acrylic fibers were hydrolyzed with sodium hydroxide to convert the CN groups on the molecular chains of the polymer to carboxylic acid groups. To increase the density of carboxyl groups on the fibers surface, citric acid was grafted to carboxylic acid groups. Furthermore, for comparison of the effect of surface area on the adsorption capacity, modified fibers were electrospun and the ability of both modified micro and nanofibers for the removal of Cu2+ and Ni2+ ions from aqueous media was evaluated. The chemical and morphological modifications of the fibers were evaluated using ATR-FTIR, thermo gravimetric analysis, and scanning electron microscopy. ATR-FTIR spectra showed reduction in the intensity of CN stretching vibrations and creation of carboxylic groups on the fibers surface. Atomic absorption spectroscopy was used to determine the ability of fibers for adsorption of metal ions from aqueous media. The modified fibers showed great ability to adsorb Cu2+ and Ni2+ ions from aqueous media.