Creation of micro and mesoporous FeIII materials utilizing organic template followed by carboxylates exchange for the low concentrations of arsenite removal

The instability of inorganic framework has been the greatest barrier to synthesize micro and mesoporous FeIII/II materials. This paper uses dodecylsulfate to organize lamellar-structure FeOx(OH)y composite followed by smaller carboxylates exchange (formate, acetate, or propionate) to create micropores. XRD, nitrogen sorption/desorption, HR-TEM, FT-IR, ICP, EPMA, TG–DTA, and Fe K-edge EXAFS measurements were used for the characterizations. The lamellar-structure reorganized to wormhole-like framework stabilized with carboxylate anions adsorbed inside micropores. Upon heating at 423 K, a half of acetates/propionates diminished and the specific surface area increased to as much as 230 m2 g−1. Based on the Fe K-edge EXAFS for FeOx(OH)y composite and derivative porous FeIII materials, Fe–O bonds were observed at 2.04–2.09 Å with the coordination number 5–6. Farther Fe⋯Fe bonds also appeared at 3.21–3.25 Å. The coordination number was obtained to 2–3, reflecting higher dispersion and higher surface area for these porous FeIII materials. The acetate-exchanged FeOx(OH)y heated at 423 K exhibited greatest saturated sorption amount (21mgAsgadsorbent-1) and equilibrium sorption constant (1.0×107mlgAs-1) in 0.2–32 ppm of arsenite test solutions among other relevant FeIII materials and FeIII nanoparticles intercalated between clay layers.