Fabrication of hyperbranched polyether demulsifier modified PVDF membrane for demulsification and separation of oil-in-water emulsion

Abstract

Membrane-based treatment for oil-in-water emulsion remains a significant challenge. The main difficulties are to solve membrane fouling and to destroy the emulsion system to achieve high-efficiency emulsion separation. Herein, chemical demulsification combined with membrane separation technology was proposed for oil/water separation from the emulsion. A hyperbranched phenol-amine resin block polyether demulsifier (AE2311) was grafted onto surface of styrene-co-maleic anhydride (SMA) blend polyvinylidene fluoride (PVDF) membrane by alcoholysis reaction. The successful preparation of the demulsifier modified PVDF membrane was characterized by X - rayphotoelectron spectroscopy (XPS), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and atomic force microscope (AFM). The obtained AE2311@SMA/PVDF membrane with grafting time of 9 h exhibited superhydrophilic (water contact angle of 0°) and underwater superoleophobic properties (underwater oil contact angle over 150°). The modified membrane can break the O/W emulsion and allow water to pass through. The separation efficiency for dichloroethane-in-water, kerosene-in-water, toluene-in-water and petroleum ether-in-water emulsions were all recorded over 99.0%, which indicates that the modified membrane has excellent capability for oil-water separation. Moreover, the modified membrane can be reused and exhibited long-term operation stability owing to the excellent underwater anti-fouling performance. The intrinsic mechanism for the oil/water separation is the synergistic effect of the chemical demulsification of AE2311, the hydrophilic and underwater super hydrophobic properties of the membrane surface, and the sieving effect of the ultrafiltration membrane. The demulsifier functionalized membrane provides a new idea for the fabrication membrane of oil-water emulsion separation in the future.