Comparative study of arsenic removal by iron-based nanomaterials: Potential candidates for field applications

Graphene oxide supported magnetite (GM) and graphene oxide supported nanoscale zero-valent iron (GNZVI) nanohybrids were compared for arsenic removal at a wide pH range (3-9). While already published work reported high process efficiency for GM and GNZVI, they cannot be compared one-on-one given the non-identical experimental conditions. Each researcher team used different initial arsenic concentration, solution pH, and adsorbent dose. This study evaluated GM and GNZVI, bare magnetite (M), and bare nanoscale zero-valent iron (NZVI) for aqueous arsenic removal under similar experimental conditions. GNZVI worked more efficiently (>90%) in a wide pH range (3-9) for both As(III) and As(V), while GM was efficient (>90%) only at pH 3 for As(V) and As(III) removal was maximum of ~80% at pH 9. GNZVI also exhibited better aqueous dispersibility with a zeta potential of -21.02 mV compared to other adsorbents in this experiment. The arsenic removal based on normalized iron content indicated that the nanohybrids recorded improved arsenic removal compare to bare nanoparticles, and GNZVI worked the best. In NZVI-based nanomaterials (GNZVI and NZVI), electrostatic attraction played a limited role while surface complexation was dominant in removal of both the arsenic species. In case of M-based nanomaterials (GM and M), As(V) removal was controlled by electrostatic attraction while As(III) adsorption was ligand exchange and surface complexation. GNZVI has the potential for field application for drinking water arsenic removal.