ABSTRACT
The current methods of constructing modification strategies for hydrophilic membranes are time-consuming, complex in operation, and poor in universality, which limit their application on membranes. In this work, inspired by the adhesion properties and versatility of caffeic acid (CA) and p-phenylenediamine (PPDA), a simple, rapid, and universal method was designed for the separation of oil-in-water emulsion by preparing a stable hydrophilic coating separation membrane. The preparation time of the membrane was shortened to 40 min. The developed PVDF-PCA/PPDA membrane showed superhydrophilic and underwater superoleophobic properties. When applied to petroleum ether-in-water emulsion, isooctane-in-water emulsion, and dodecane-in-water emulsion separation, the oil rejection was more than 99.0%. In the circulating separation of 10 g/L soybean oil-in-water emulsion, the oil rejection was more than 99.3%, and the highest flux was 1036 L·m-2·h-1. The prepared PVDF-PCA/PPDA membrane performed well in the separation test of oily wastewater. The proposed strategy is simple and rapid; it may become a universal method for preparing membranes with super strong antifouling properties against viscous oil and accelerate the research progress of membrane separation of oil-in-water emulsions.
ABSTRACT
Plant polyphenol-inspired surface modification of membranes is helpful for oil-water separation. However, the preparation of this coating is time-consuming. Herein, we introduce a rapid synthesis of the TA-APTES coating by the addition of sodium periodate (SP). The surface chemical composition and morphology of the resultant TA-APTES hybrid coatings were characterized using SEM, ATR-FTIR, and XPS. The hydrophilicity and membrane performance were investigated by the water contact angle, pure water permeability, and oil rejection for an isooctane-in-water emulsion. The experimental findings revealed that the optimal microfiltration (MF) membrane (MF-TA-APTES-SP-0.05) displayed exceptional hydrophilicity and water permeability (9558 L m-2 h-1 bar-1). The membrane realized highly efficient separation with a permeability (4117 L m-2 h-1 bar-1) and rejection of oils (>99%). Furthermore, it possessed outstanding chemical stability and maintained underwater superoleophobicity even after exposure to harsh conditions. This simple and rapid strategy of developing hydrophilic coatings as a modifier for the poly(vinylidene fluoride) membranes has potential applications in oil-water separation and wastewater treatment.
