Synthesis of a maghemite-polypyrrole nanocomposite for the removal of congo red dye from aqueous solutions

A magnetic nanocomposite (MNC) of γ-Fe2O3 nanoparticles (NPs) and polypyrrole (PPY) was synthesized by in-situ chemical oxidative polymerization of pyrrole in presence of FeCl3 as oxidizing agent in order to evaluate its adsorption capacity of Congo red (CR) in aqueous solutions. γ-Fe2O3 NPs were first synthetized by a co-precipitation method with an average particle size of 14 ± 8 nm. In a subsequent step, the MNC was synthesized by the polymerization of pyrrole in an aqueous solution containing the γ-Fe2O3 NPs. The resulting material consisted of maghemite NPs embedded within the polymeric matrix of PPY. The magnetization curves demonstrated the superparamagnetic behavior of the γ-Fe2O3 NPs at room temperature (Ms = 60 emu/g), while the magnetization value of the γ-Fe2O3/PPY MNC decreased up to 14 emu/g. We evaluated the CR adsorption removal of the MNC as a function of the pH, interaction time and the initial dye concentration. The maximum adsorption capacity (qe) achieved was 269.5 mg/g at pH 7.0 and 60 min of interaction time. The present work shows the production of an effective and economic magnetic adsorbent for the removal of dyes from aqueous solutions.