Synthesis of polyaniline–magnetite nanocomposites using swollen liquid crystal templates for magnetically separable dye adsorbent applications

Abstract

Solid phase extraction of pollutants requires the adsorbents to have high adsorption capacities, ease of separation and fast adsorption–desorption kinetics. Here we describe the development of magnetically separable adsorbents for dyes based on nanocomposites of polyaniline–iron oxide having a unique rod like morphology of polyaniline in which nanowires of iron oxide are embedded. Polyaniline–iron oxide nanocomposites having unique morphology were synthesized using swollen liquid crystals (SLCs) as soft structure directing agents. The SLCs are formed from a quaternary mixture of aqueous phase, oil phase, surfactant and co-surfactant. Mesophases of aniline or ferric chloride were synthesized by trapping a small amount of aniline in the oil phase or by replacing the brine phase with aqueous ferric chloride in the SLCs, respectively. The unique morphology of the nanocomposites enables them to adsorb dyes rapidly from an aqueous medium. Moreover, the adsorption kinetics could be modelled using a pseudo second order reaction indicating that the adsorption was not limited by mass transport, probably due to the short diffusion lengths in the nanocomposites. The nanocomposites showed adsorption based on electrostatic interaction and had very high adsorption capacities of upto ∼100 mg g⁻¹.