Adsorption study on removal of Cr(VI) ions by polyaniline composite

The polyaniline composite composed of 0.2 mol L-1 aniline and 2% w/v polyvinyl alcohol was prepared by in situ polymerization technique. When this polyaniline/polyvinyl alcohol (PANI/PVA) composite was used as an adsorbent, it removes Cr(VI) ions from water effectively. Further investigations using FTIR, SEM-EDX, and XRD reveal that this composite has a unique structure and morphology, which favors higher Cr(VI) ion adsorption with the maximum sorption capacity of 111.23 mg of Cr(VI)/0.1 g of adsorbent. Subsequently, results from a batch adsorption system suggest that it requires relatively less contact time (60 min) at pH 4 with the initial concentration range of Cr(VI) ions (200 mg L-1). Adsorption of Cr(VI) by PANI/PVA composite obeys Freundlich isotherm. Furthermore, the nature of Cr(VI) sorption is found to be spontaneous and endothermic which does not require any pre-treatment. It follows the pseudo-second-order kinetics and resembles pore diffusion model. Overall, the Cr(VI) removal by composite is driven by the adsorption-coupled reduction. Considering all these unique characteristics, the composite can be considered for potential removal of Cr(VI) from aqueous solution on a larger scale.