Synthesis of magnetic orderly mesoporous α-Fe₂O₃ nanocluster derived from MIL-100(Fe) for rapid and efficient arsenic(III,V) removal

A calcination time regulation method has been unprecedentedly used to adjust the orderly meso-structure of novel α-Fe₂O₃ nanoclusters derived from MIL-100(Fe) (MIL: Materials of Institute Lavoisier). The as-synthesized magnetic orderly mesoporous α-Fe₂O₃ nanoclusters were characterized by XRD, SEM, TEM, TGA, N₂ adsorption-desorption isotherms, VSM, Zeta potential, FTIR and XPS. The 6h calcinated α-Fe₂O₃ nanocluster exhibited the optimal properties, including the high specific surface area and the orderly mesoporous properties, which facilitate the arsenic(III,V) adsorption capacity. The maximum adsorption capacities of As(III) and As(V) were 109.89 and 181.82mgg^-1, respectively, and adsorption equilibrium can be reached just within 30min. The kinetics intra-particle diffusion model and adsorption isotherms reveal that the adsorption rate is controlled by pore diffusion and the adsorption process belongs to Langmuir monolayer adsorption. These results indicate that the orderly mesoporous structure of α-Fe₂O₃ nanoclusters plays a key role in rapid and efficient adsorption for arsenic(III,V). Meanwhile, adsorption mechanism verifies that arsenic can react with active sites (Fe-OH) to form complexes by Fe-O-As bond. Moreover, α-Fe₂O₃ nanocluster can be separated easily due to its excellent magnetism. Above all, the magnetism orderly mesoporous α-Fe₂O₃ nanocluster is a promising adsorbent for emergent treatment of arsenic in practice.