Reformulated FeOOH Acetate Nanoplatelet for Heavy Metal Immobilization

Arsenic is a heavy metal that contaminates the ecosystem and originates global damage to a sustainable environment.¹ The attempt to immobilize arsenic using neither nanostructure-engineered material nor natural nanomaterials is suggested due to its productivity and potential to harm the ecosystem in the soil.²<br/>Here, we suggest a method to enhance the arsenic immobilization via using sustainable nanomaterial amendment, reformulated FeOOH-acetate nanoplatelets (FAN). Iron oxyhydroxide is a clay mineral that is abundant in the earth's crust and is a sustainable natural material.³ FAN is synthesized either by reformulating the natural iron oxyhydroxide form or by the particle attachment-based synthesis, both in an expandable scale. In the crystallization process of FAN, acetate anions are coordinated to the iron atom with bidentate bridging, inducing a stacking of FeO₆ octahedron layers with a large spacing. It has an inorganic-organic hybrid structure with an extended lepidocrocite layered structure with a basal spacing of 1.14 nm. FAN immobilizes arsenic by two mechanisms, electrostatic intercalation with a large interlayer spacing and chemical adsorption on the surface of layers. This synergetic adsorption mechanism enables FAN to enhance the adsorption capacity of arsenic species acting as sustainable engineered nano-amendments. The ability to immobilize the bioavailable arsenic is confirmed with the bioassay of collembolan and plant reproduction, and arsenic adsorption results in arsenic-contaminated artificial soil and mine soil. This research will be the basis for crystallization-based engineering of natural materials for a sustainable environment.<br/><br/>[1] Duker, A. A., Carranza, E. J. & Hale, M. Arsenic geochemistry and health. <i>Environ. Int.</i> <b>31</b>, 631–641 (2005).<br/>[2] Titirici, M. et al. The sustainable materials roadmap. <i>J. Phys. Mater.</i> <b>5</b>, 032001 (2022).<br/>[3] R. B. Frankel, Iron Oxides: From Nature to Applications, 1st edition (Wiley-VCH, 2016)