Chitosan-derived iron oxide systems for magnetically guided and efficient water purification processes from polycyclic aromatic hydrocarbons

Chitosan and pyrolyzed chitosan, acting as protective frameworks of magnetic nanoparticles (magnetite/maghemite and/or metallic Fe), have been investigated to be used in magnetically guided water remediation processes from polycyclic aromatic hydrocarbons (PAHs). Chitosan-derived magnet-sensitive materials were first obtained by a one-step coprecipitation method, and then two carbon-derived magnetic chitosan materials were obtained under N2 gas flow at 550 and 800 °C, respectively. The obtained materials were investigated by means of X-ray diffraction (XRD), FTIR spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), magnetic force microscopy (MFM), and magnetization measurements. Thermal treatment conditions, along with the amounts of chitosan used in the synthesis processes, played a critical role in the crystal structure and magnetic properties of the obtained nanomaterials. The adsorption capacity of chitosan-derived magnet-sensitive materials was tested toward PAHs. The results indicate high sorption capacity for anthracene and naphthalene onto the chitosan-derived material pyrolyzed at 550 °C. Furthermore, experiments performed with a mixture of eight PAHs show that PAH molecules with higher hydrophobicity and more extended aromaticity had stronger sorption capacity. Interestingly, due to the obtained results, the use of chitosan is encouraged as a platform for the creation of green adsorbents for further developments in wastewater purification treatments