Superwetting membranes with in-situ ZIF-90 immobilization during phase inversion: A synchronous strategy for high-performance emulsion separation and heavy metal adsorption

Superwetting membrane have gained significant attention as a highly effective solution for oily wastewater treatment. However, its effectiveness was restricted when separating different types of oil-in-water (O/W) and water-in-oil (W/O) emulsions due to the limited single wettability of the membrane surfaces. Developing superwetting membranes with broad applicability and high separation efficiency is crucial for the continued advancement of membrane separation technology. In this study, a hydrophilic polymer, poly 2-hydroxybutyl methacrylate (PHBMA) was introduced into the polyacrylonitrile (PAN) substrate, and zeolitic imidazolate framework-90 (ZIF-90) particles were synchronously grown and in-situ immobilized on the membrane surface in process of phase inversion, forming a ZIF-90@P-PAN membrane with switchable superwettability. With increasing ZIF-90 growth time, the membrane surface first became rougher due to crystal formation, then gradually denser as particle accumulation increased. This membrane exhibited super-amphiphilicity in air and super-amphiphobicity under liquid, demonstrating high permeation flux and excellent separation efficiency (>99 %) for different types of emulsions. The effects of ZIF-90 particles with different growth times on the membrane morphology, wettability and oil–water separation performance were systematically studied. Additionally, the removal efficiency (>80 %) and recycling performance of the ZIF-90@P-PAN membrane for four different heavy metal ions were investigated. This work contributed to the development of superwetting membranes for efficient recovery of oily wastewater.