Preparation of GO/MIL-101(Fe,Cu) composite and its adsorption mechanisms for phosphate in aqueous solution.

In this study, MIL-101(Fe), MIL-101(Fe,Cu), and graphene oxide (GO)/MIL-101(Fe,Cu) were synthesized to compose a novel sorbent. The adsorption properties of these three MOF-based composites were compared toward the removal of phosphate. Furthermore, the influencing factors including adsorption time, pH, temperature, and initial concentration on the adsorption capacity of phosphate on these materials as well as the reusability of the material were discussed. The structure of fabricated materials and the removal mechanism of phosphate on the composite material were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, and zeta potential. The results show that the maximum adsorption capacity of phosphate by the composite GO/MIL-101(Fe,Cu)-2% was 204.60 mg·g-1, which is higher than that of MIL-101(Fe,Cu) and MIL-101(Fe). likewise the specific surface area of GO/MIL-101(Fe,Cu)-2% is 778.11 m2/g is higher than that of MIL-101(Fe,Cuand MIL-101(Fe),which are 747.75 and 510.66 m2/g, respectively. The adsorption mechanism of phosphate is electrostatic attraction, forming coordination bonds and hydrogen bonds. The fabricated material is a promising adsorbent for the removal of phosphate with good reusability.