Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g(-1) of AG at pH 4 and 81.3 mg g(-1) of MB at pH 11. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47056.