(Maghemite/Chitosan/Polypyrrole) nanocomposites for the efficient removal of Cr (VI) from aqueous media

We report the preparation of a new hybrid magnetic nanocomposite (HMNC) based on maghemite (gamma-Fe2O3), chitosan (Chi), and polypyrrole (PPY), and its use in water remediation protocols. We prepared the gamma-Fe2O3 nanoparticles by a coprecipitation route in the presence of chitosan, whose role is to envelop the nanoparticles, easing the posterior incorporation of PPY chains. We characterized the resulting hybrid composites by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared (FTIR) spectroscopy, water contact angle, and magnetic measurements. The gamma-Fe2O3@Chi@PPY HMNC exhibited spherical morphology, with an average diameter of 34 nm, and a saturation magnetization of 9.8 emu.g(-1). Due to this characteristic, these composites can be easily removed through the application of an external magnetic field. The HMNC showed their best capacity of removing Cr (VI) ions from aqueous media at pH 2.0, attaining a 100% degree of capture for concentrations below 10 mg.L-1, with a maximum removal capacity (301.2 mg.g(-1)) that is higher than those of other polypyrrole based materials discussed in the literature. Recycling studies showed that the HMNC presented excellent performance and could be reused in at least five consecutive adsorption/desorption cycles without significant losses in their original adsorption capacity. For allying high adsorbing characteristics to a simple manner of removal of the captured contaminant from aqueous media, this gamma-Fe2O3@Chi@PPY HMNC appears as a very promising platform for wastewater treatment.

Automated summary

In this study, a new hybrid magnetic nanocomposite (HMNC) based on maghemite, chitosan, and polypyrrole was prepared and utilized for water remediation protocols. The HMNC showed excellent removal capacity for Cr (VI) ions in aqueous media and demonstrated high reusability through multiple adsorption/desorption cycles. The hybrid composites offer a promising platform for wastewater treatment due to their high adsorption capabilities and easy removal of captured contaminants.