An in situ approach to entrap ultra-small iron oxide nanoparticles inside hydrophilic electrospun nanofibers with high arsenic adsorption

Abstract

The problem of arsenic contamination in water demands sustainable, scalable, and easy-to-implement solutions. Various nano-adsorbents flourished in the last decade, but their use alone requires additional filtering processes to avoid environmental contamination. This work presents a simple, efficient, green approach to overcome this inconvenience while maximizing adsorption capacity. We show for the first time a novel approach to synthesizing ultra-small nanoparticles (IONPs) within electrospun hydrophilic poly(vinyl alcohol) (PVA) nanofibers, avoiding NPs release into the environment when submerged in water. The in-situ synthesis favor enhanced arsenic adsorption capacity due to the excellent dispersion, tiny size, and surface availability of IONPs, reaching 3.5 mg/g at 10 μg/L. We show that IONPs alter the polymeric matrix properties, such as the glass transition temperature and crystallinity, by preventing the formation of strong hydrogen bond inter/intramolecular interactions of PVA. Insolubility and swelling capacity are essential characteristics of this membrane, which allow solution interchange for arsenic adsorption onto IONPs. Isotherm studies show that the increase from 1 wt% to 3 wt% of IONPs content decreases the active sites for adsorption per mass of IONPs. Still, it does not alter the reusability of the membrane, which reaches at least 3 adsorption cycles with 80 % efficiency. We discuss the adsorption mechanisms and show that phosphate anions partially inhibit As(V) adsorption and that the membranes are also highly capable of removing Cr(VI), independently of the presence of Ni(II).