Well-dispersed magnetic iron oxide nanocrystals on sepiolite nanofibers for arsenic removal

A novel nanostructure composed of magnetic iron oxide nanocrystals (MI) anchored on a sepiolite nanofiber backbone with excellent arsenic adsorption performance has been successfully developed. Sepiolites (SEPs) as typical nano-geomaterials with low cost, large specific surface (ca. 300 m2 g−1) and tunable surface chemistry are chosen as the host matrix. Transmission electron microscopy confirms that uniform Fe2O3 nanocrystals with an average particle size of ∼9 nm are spatially well-dispersed and anchored on the sepiolite backbone at a high Fe2O3 content of 33.2 wt%, rather than forming aggregates on the external surface. MI/SEPs have a high specific surface area, high loading amount, the non-aggregated nature of Fe2O3 nanocrystals, good dispersion and magnetic properties, making them promising for use as a separable adsorbent for As(III) removal with high adsorption capacity and magnetic separation properties. The maximum adsorption capacity has a wonderful value of 50.35 mg g−1 for As(III) on the MI/SEPs, which is higher than those of previously reported adsorbents. Moreover, MI/SEPs can reduce the concentration of As(III) from 140 to 1.5 μg L−1. MI/SEPs also show high removal ratios of 96.4% without any pre-treatment in real groundwater with an arsenic concentration of 456.5 μg L−1.