Development of a powerful zeolitic imidazolate framework (ZIF-8)/carbon fiber nanocomposite for separation of hydrocarbons and crude oil from wastewater

Pollution from crude oil spills is a global concern owing to its destructive effect on the environment; in particular, the aquatic life. In this work, a facile synthesis method is applied to produce a novel highly hydrophobic zeolitic imidazolate framework (ZIF-8) coated onto carbon fiber (CF) fabric as a substrate without pre-modification. The product ZIF-8/CF was characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and surface area estimation as well as sorption and desorption tests. The porous structure of ZIF-8/CF consisted of fixed layers of carbon fabric and nanocrystalline ZIF-8. The ZIF-8 crystals increased the water contact angle of the carbon fabric to 150°, whereas the oil contact angle was nearly 0°, creating a shield toward water penetration. ZIF-8/CF displayed high porosity, strong hydrophobicity, low density and high sorption capacity of the hydrocarbons; up to 24 times its weight. Recycling of the sorbed hydrocarbons and crude oil was achieved by squeezing the organic out of the ZIF-8-CF, followed by simple heating to 80°C and two-stage washing of the sorbent using toluene and acetone, respectively. The ZIF-8/CF exhibited excellent reusability and recyclability (up to 20 cycles), without losing its efficiency, proving its high potency for cleaning up oil spills.