Surface-modified polyacrylonitrile nanofibers as supports

Polyacrylonitrile nanofibers (PAN-nfs) are one of the most studied nanofibres because of their excellent characteristics, such as good mechanical strength, chemical resistance, and good thermal stability. Due to the easy dissolution in polar organic solvents, PAN-nfs are mostly produced via electrospinning technique. The electrospun PAN-nfs surfaces are relatively in-active and hydrophobic, and, therefore, hinder some potential applications; however, chemical surface modification reactions, such as amination, reduction, hydrolysis, and amidoximation, have been carried out on them. These reactions bring about functional groups, such as amine, hydroxyl, carboxylic, imine etc, to the surface PAN-nfs and invariably make their surfaces active and hydrophilic. The surface-modified PAN-nfs have been used as supports for organic compounds, enzymes, and antibodies in biological studies. They have also been used for immobilization of various organic ligands for adsorption of metal ions in water. Furthermore, because of their ability to complex metal ions, several surface-modified PAN-nfs have also been used as supports for transition metal catalysts in Fenton’s chemistry.IS

Metal adsorption behavior of 2,4-dinitrophenyl hydrazine modified polyacrylonitrile nanofibers

Electrospun polyacrylonitrile nanofiber mats (es-PAN nanofiber mats) were surface modified by 2,4-dinitrophenyl-hydrazine (2,4-DNPH) to yield the metal ion adsorption material (es-PAN-DNPH nanofiber mats) and were investigated their adsorption behaviors. Functional modification of the es-PAN nanofiber mats and conventional polyacrylonitrile fibers (c-PAN fibers) were prepared by using 4% (w/v) of 2,4-DNPH in 1,2-ethandiol at 110°C for 6 h to obtained c-PAN-DNPH fibers. The average diameter of the es-PAN-DNPH nanofiber mats was 0.25 µm, which was comparatively smaller than the es-PAN precursor. Their functional groups were confirmed by Fourier transform infrared spectroscopy (FT-IR) and their adsorption behaviors to trace Ag(I), Bi(III), Ga(III), and In(III) from aqueous solutions and were investigated by the induced couple plasma technique. The FT-IR spectra showed the existence of NN=C–NHNH–, O=C–NHNH–, and –NO2 functional groups for metal complexes. The adsorption capacities of the obtained es-PAN-DNPH were 7.14 to 36.36% higher than those of c-PAN-DNPH fibers. All adsorption plots onto es-PAN-DNPH nanofiber mats and c-PANDNPH fibers followed the Langmuir isotherm and indicated monolayer adsorption characteristics