Application of sand particles modified with NH2-MIL-101(Fe) as an efficient visible-light photocatalyst for Cr(VI) reduction.

This study presented chemical immobilization of an iron(III)-based metal-organic framework [NH2-MIL-101(Fe)] on the surface of sand particles and its application for Cr(VI) photocatalytic reduction using visible light. The surface of sand particles was functionalized with (3-chloropropyl)trimethoxy silane to provide the active sites for bond formation with MOF particles. Using a heat treatment step, MOF particles were bonded on the surface of sand particles, thereby providing a photocatalyst more applicable in real environments. The presence of amino-functional groups in MOF was influential in bond formation. Furthermore, they are effective in the activation of the photocatalyst under visible-light irradiation. The photocatalyst properties were investigated by FESEM, FTIR, XPS, EDS, and DRS analysis. The impact of various parameters, such as light power, irradiation and contact time, TDS impact, and pH, was examined. The composite produced by immobilization of NH2-101(Fe) on the surface of sand-Cl showed the high Cr(VI) removal efficiency (80% at 20 mg L-1) as a result of the strong chemical bond formation through the suitable functional groups incorporated in materials. Under the optimum conditions, the reduction rate reached more than 99% using irradiation by 1000 W visible light for 30 min.