Comparative analysis of absorption capacity of Cr(VI) polyaniline and cellulose/polyaniline composites synthesized in aqueous solutions of organic acids

Abstract

Samples of polyaniline (PAn) doped by different organic acids, namely PAn-FA, PAn-AA, PAn-OA, and PAn-CA, were synthesized by oxidation of aniline (An) with ammonium peroxydisulfate in the 0.5 M aqueous solutions of formic (FA), acetic (AC), oxalic (OA), and citric acids (CA) respectively. Samples of composites of cellulose (Cel) with doped polyaniline (Cel/PAn-FA, Cel/PAn-AA, Cel/PAn-OA, and Cel/PAn-CA)were produced by the same method under the presence of a suspension of microfibrillar bleached cellulose in the reaction mixture. The mass ratio of An : Cel was 1 : 1. The structure of obtained samples was studied using X-ray diffraction, FTIR spectral analysis, and scanning electron microscopy. Adsorption capacity as concerns Cr(VI) by produced samples of both individual polyanilines and composites and adsorption kinetics has been studied by electronic (UV) and fluorescence X-ray spectroscopy and also X-ray energy dispersion analysis methods. Practically full removal of Cr(VI) ions (98–100 %) of such investigated samples of PAns and its composites has been determined. The adsorption kinetics is well described by equations of pseudo first and second orders. According to the results, the Langmuir and Freundlich adsorption isotherms are plotted. It was found that the process of adsorption Cr(VI) ions by doped samples of PAn and Cel/PAn accords to adsorption model of Langmuir. It has been shown, that adsorbed chromium remains in the samples of adsorbents in the form of chromium (III). Keywords : polyaniline, cellulose, composites, structure, Cr(VI), adsorption.