Surface modification of electrospun PAN nanofibers by amine compounds for adsorption of anionic dyes

Within the present study, polyacrylonitrile (PAN) nanofibers were produced by electrospinning technique. The surface of the webs was then modified by three different sources of amine-containing compounds, including diethylamine, diethylenetriamine, and triethylenetetramine. Chemical, morphological, and surface properties of nanofibers were investigated by attenuated total internal reflection (ATR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The maximum grafting yield of amine groups to PAN nanofibers was calculated by the gravimetric method. The ATR results indicated that amide groups were formed on the fiber surface by a chemical reaction between the nitrile groups of PAN and the amine groups of amine-containing compounds. The SEM images showed a rough, conglutinated, and intertwined surface morphology of nanofibers induced by amine-containing materials. The AFM results showed that after the functionalization process, the surfaces of the PAN nanofiber were rougher when compared with untreated PAN nanofiber. Finally, their dye removal ability was evaluated using UV-vis spectroscopy using Direct red 80 (DR80) and Direct red 23 (DR23) as model compounds. The amounts of the dye adsorbed onto the functionalized PAN nanofibers (FPAN) were influenced by the initial pH, FPAN dosage, contact time, and the initial concentration of the dye solutions. It was found that both dyes adsorption followed the Langmuir isotherm. In addition, adsorption kinetics of both dyes was found to conform to pseudo-second-order kinetics. We finally found that the functionalized PAN nanofibers were good candidates for anionic dye adsorption from colored wastewater with high dye adsorption capacity