Synthesis of MIL-101@nanoporous graphene composites as hydrophobic adsorbents for oil removal

Abstract

Abstract The marine environment is being more and more polluted by oil spills on a daily basis, posing a serious threat to humans. The substances possessing high adsorption capacity and hydrophobic nature, generally play an important role in crude oil adsorption from aqueous solutions. The synthesis of new porous materials has attracted attention of many researchers in a large number of systems. Metal Organic Frameworks such as MIL-101(Cr) with high surface area and pore volume have been widely investigated to use in many applications such as separation. To enhance the MIL-101′s properties, hybrid composites with high specific surface area and pore volume have been considered. MIL-101 and MIL-101@ nanoporous graphene (NPG), which have been fabricated for the first time, with different nanoporous graphene contents (30, 60, and 90 wt%) were herein synthesized via a solvothermal method .The prepared adsorbents were characterized using field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR spectroscopy, thermal gravimetric analysis (TGA), adsorption of nitrogen at 77.4 K, and contact angle (CA). The high oil adsorption capacity (14 g/g) was achieved for the synthesized adsorbents with the high surface area of MIL-101 (4293 m2/g) and MIL-101@NPG 60 wt% (4642 m2/g), and the high pore volume of MIL-101 (2.42 cm3/g) and MIL-101@NPG 60 wt% (2.62 cm3/g). The results show that the crude oil adsorption capacity enhanced by adding NPG to the virgin MIL-101, which is higher than that of previous scientific reports. The conformity of various adsorption models, including Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich (D-R) to the equilibrium data were evaluated, and among which Freundlich isotherm model gave the best fitting result. The synthesized adsorbents can be further reused for several times, with no significant adsorption loss capacity and hydrophobicity.