Synthesis, physicochemical characterization and Cr(VI) adsorption study of functionalized polyaniline-polyamide nanocomposites

Abstract Polyaniline and polyamide have electron-active sites, which make them one of the most attractive materials for the adsorption of Cr (VI) from aqueous media. Their adsorption capacity for Cr (VI) can be enhanced through modification and blending techniques. In this study, sulfonated polyaniline–nylon 6 (SPAN–Ny6) nanocomposites were synthesized via in-situ oxidative polymerization of aniline using ammonium persulfate as an initiator in a formic acid medium. Concentrated sulfuric acid was added dropwise in the presence of 15%, 30%, 50%, and 70% aniline relative to nylon 6. Then, these nanocomposites were identified and characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and thermogravimetric analysis, and their morphology was studied by field emission scanning electron microscopy (FE-SEM). Conductivity of the prepared nanocomposites was also measured using the four-point method, and the highest measured conductivity was 0.248 S cm −1 for the SPAN-Ny6-70% nanocomposite. Additionally, the processability of the nanocomposites was studied by the electrospinning technique in formic acid as a solvent. Morphology of the nanofibers was identified by FE-SEM. The hydrophilicity of the nanofibers was investigated by contact angle analysis, which indicated a significant decrease in hydrophilicity of the nanocomposites with increasing percentage of polyaniline sulfonate. Subsequently, the synthesized nanocomposites were used to absorb the Cr (VI) contamination from aqueous solutions after optimizing the adsorption pH, time, temperature, and initial chromium ion concentration. The adsorption isotherm and kinetics were studied in optimized conditions, which revealed that the adsorption process was consistent with the Langmuir isotherm and pseudo-second-order kinetic model.