Durable polyvinylpyrrolidone superhydrophilic modified ZIF-8 mesh membrane for gravitational oil-water separation and oil recovery

Developing a superhydrophilic/underwater oleophobic mesh membrane using an economical and eco-friendly method is still challenging to achieve high efficiency for oily wastewater separation. In this study, we proposed a novel approach to fabricate superhydrophilic/underwater oleophobic PVP/ZIF-8 coatings on stainless steel (SS) mesh using a low-cost and environmentally friendly electrodeposition method. The prepared PVP/ZIF-8@SS mesh membrane exhibited remarkable self-cleaning and anti-oil-fouling properties, along with a strong chemical robustness in extreme environments. Additionally, the mesh membrane demonstrated strong antimicrobial ability and excellent corrosion resistance property. The mesh membrane also showed promising potential in gravitational oil-water separation and oil recovery, achieving a separation efficiency of 99.0% and a water flux of 3.8 × 103 L·m−2·h−1 for rapeseed oil-water mixtures. Importantly, the PVP/ZIF-8@SS mesh membrane maintained exceptional separation efficiency, high water flux, and underwater oleophobicity properties even after undergoing 35 cycles of oil-water separations. The oil-water separation mechanism of the PVP/ZIF-8@SS mesh membrane suggested that the surface of the mesh membrane contained PVP/ZIF-8 particles with a significant negative charge. These particles preferentially interacted with positively charged water, facilitating the rapid passage of water phase through the pores, while impeding the permeation of negatively charged oil phase. This research provides an effective strategy for practical applications, including marine oil spill cleanup, oily wastewater treatment, and recycling of residual cooking oil in the restaurant industry.