Preparation of temperature-dependent flux controllable cellulose nanofiber-based films and their application in oil-water separation

Abstract

The discharge of industrial oily wastewater causes a significant waste of resources and serious environmental pollution problems. Oil- water separation and recycling waste oil are effective ways for human society to achieve sustainable development. In this work, a series of temperature dependent flux adjustable “dehydration type” cellulose nanofiber-based (CNFS) films was constructed for achieving efficient oil-water separation, which were obtained by using physical blending of polyvinyl alcohol (PVA) and cellulose nanofibers (CNF) modified by sulfobetaine fragment (SB). CNFS-based films with high SB content had high water flux. At room temperature, after 20 cycles, the water flux of CNFS-5/15%PVA film was 881 L m⁻² h⁻¹ for separating petroleum ether/water lotion, and the oil-water separation efficiency was 93.4 %. CNFS-based films exhibited higher water fluxes at high temperatures. For example, at 35 °C, the water flux of CNFS-5/15%PVA film was 1.5 times that at room temperature. The higher water flux of CNFS-based films at high temperatures was attributed to their higher hydrophilicity. In this work, SB was used to endow CNF with temperature response. And the CNFS-based films can effectively separate oil lotion by regulating the water fluxes through temperature, which provides a new idea for oil-water separation and recycling waste oil.