Graphene Oxide Supported Metal Oxide Nanohybrids for Groundwater Arsenic Removal

Abstract Submission: In this work, two graphene oxide (GO)-Fe nanohybrids, namely GO-supported nano magnetite (GM) and GO-supported nanoscale zero-valent iron (GFeN), were compared for arsenic removal. Based on normalized iron content in the adsorbents, the nanohybrids (GFeN and GM) removed arsenic more efficiently compared to the bare nanoparticles with GFeN performing the best. In GFeN and FeNP, surface complexation was dominant in the adsorption of both As(III) and As(V), and electrostatic attraction played a limited role. In GM and M, As(V) removal was controlled by electrostatic attraction while As(III) adsorption was ligand exchange and surface complexation. Arsenic adsorption capacities of GFeN were found to be 306 mg/g for As(III) and 431 mg/g for As(V). The GO-sheets in GFeN acted as reservoirs for the electrons released during surface corrosion of the FeNPs. The stored electrons were transferred back to the FeNPs to reduce the oxidized iron surface, and the rejuvenated surface helped in additional arsenic removal. The arsenic desorption pattern from two As(V)-sorbed nanohybrids (GFeN and graphene oxide-supported ceria (GO-CeO2)) was studied. GFeN released ~5.73% and GO-CeO2 released ~0.94% of sorbed arsenic over a period of two years. The surface oxide composition in GFeN (FeOOH and Fe2O3) and GO-CeO2 (Ce3+/Ce4+ ratio) changed over time and that played a role in arsenic desorption.

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