Direct epitaxial synthesis of magnetic Fe3O4@UiO-66 composite for efficient removal of arsenate from water

Facile fabrication of magnetic metal-organic frameworks (MOFs) using a direct epitaxial approach for eliminating arsenic from water is highly desirable. Herein, a two-step solvothermal method of elegant design is proposed to synthesize Fe3O4@UiO-66. Such resulting composite was systematically characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FUR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 adsorption-desorption isotherms, and thermogravimetric analysis (TGA). Results clearly reveal that this novel composite exhibits a unique core-shell structure with high specific surface area and plentiful micropores as well as good thermal stability. Specifically, batch adsorption data for arsenate demonstrate that a pseudo-second order kinetic model (R-2 = 0.9996) better describes this adsorption process than a pseudo-first order model (R-2 = 0.8582), revealing the chemical interaction between the composite and arsenate. The Freundlich model with better coefficient (R-2 = 0.9566) further verified multi-layer heterogeneous adsorption, which may be ascribed to the unique core-shell structure of this composite (Fe3O4@UiO-66). Its excellent adsorption performance for arsenate (73.2 mg (As) g(-1) (adsorbent)) is comparable to most MOFs-containing adsorbents but is also magnetic, allowing for ready separation of the composite from aqueous solution. Given this combination of qualities, this new composite could offer a promising alternative for wastewater remediation.