Simple route for the generation of differently functionalized PVC@graphene-polyaniline fiber bundles for the removal of Congo red from wastewater

This paper reports a simple route for the generation of fibrous polyvinyl chloride (PVC) and graphene (GN) fibers (PVC@GN). The prepared fibrous PVC@GN was functionalized further with polyaniline (Pani) via simple in situ oxidative polymerization to prepare PVC@GN-Pani fibers. The resulting PVC@GN-Pani fibers were treated with HCl, NH4OH and cetyltrimethylammonium bromide (CTAB) to impart additional functionality. The fibers were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible diffuse absorbance spectroscopy. The applications of differently doped fibers to the adsorptive removal of Congo red (CR) dye were assessed. The results showed that the surfactant, CTAB, doped, i.e., PVC@GN-Pani-s, has the highest adsorption capacity for CR removal compared to the acid doped, i.e., PVC@GN-Pani-a, and base treated, i.e., PVC@GN-Pani-b fibers. The maximum removal of CR was observed at pH 4.5 suggesting that pH plays an important role in the dye adsorption process. The thermodynamic parameters showed that a low temperature favors the adsorption of CR onto all the fibers studied. The adsorption equilibrium data was fitted to the Langmuir and Freundlich adsorption isotherm models. The best fitted results were obtained using the Langmuir model indicating monolayer adsorption of CR onto the PVC@GN-Pani-b, PVC@GN-Pani-a and PVC@GN-Pani-s surfaces. This study showed that these functionalized PVC@GN-Pani nanofibers can be potential adsorbents for the removal of organic pollutants from aqueous solution.