Adsorptive removal of methyl orange with polyaniline nanofibers: an unconventional adsorbent for water treatment

Abstract

ABSTRACT The present study reports the adsorptive removal of methyl orange (MO) from its aqueous solution by the utilization of polyaniline (PANI) nanofibers. PANI nanofibers were synthesized by the conventional interfacial polymerization method using ammonium persulphate as an oxidant in an acidic medium. The average diameter of the synthesized PANI nanofibers was found to be 60 ± 5 nm as detected by high resolution transmission electron microscope and scanning electron microscope techniques. The synthesized PANI nanofibers were characterized by fourier transform infrared spectroscopy, X-ray diffraction, UV–VIS spectroscopy, Brunauer-Emmett-Teller surface area analyzer (BET), zero energy thermonuclear apparatus and four-probe conductivity techniques and were further used for the adsorption of the MO dye from its aqueous solution using batch mode experiments. Due to their positively charged backbone, PANI nanofibers are found to be suitable for the adsorption of anionic dyes such as MO. The BET surface area of the synthesized polyaniline nanofibers was found to be 48.83 m2 g−1 (higher than conventionally synthesized polyaniline). The influence of important adsorption parameters, i.e. initial dye concentration, pH and duration of contact was also studied, and the equilibrium values of these parameters are noted to be 7 mg L−1, pH ∼7 and 80 min, respectively. The experimental data were found to be best fitted to the pseudo-second order model (R 2 = 0.99). The Freundlich isotherm was found to be best fitted for the adsorption of MO onto PANI nanofibers with R 2 = 0.91.