Polyethylenimine-Modified Glass Fiber by a Sulfur-Based Coupling Reaction for Selective Demulsification of Oil/Water Emulsions

Separating oily wastewater, especially surfactant-stabilizedemulsions,is an urgent problem to solve because of its severe threats to theenvironment and human health. Polyethylenimine (PEI) molecules withabundant amine groups could reduce the stability of emulsions. Herein,PEI-modified glass fiber (GF) was fabricated using a facile and effectivesurface modification strategy: a sulfur-based three-component couplingreaction between PEI and (& gamma;-aminopropyl)triethoxysilane-treatedGF. After wet-laying the fabric, the obtained membranes presentedsuperamphiphilicity in air, underwater superoleophobicity, and positivesurface charges in water. Based on electrostatic and hydrogen-bondinteractions originating from PEI, the prepared membranes exhibiteddifferent separation efficiencies from the oil-in-water emulsionsprepared using anionic, nonionic, zwitterionic, and cationic surfactants.The separation efficiency was only 31.8% for the emulsion stabilizedby a cationic surfactant and raised to over 94.7% for the emulsionstabilized by anionic, nonionic, and zwitterionic surfactants. Inparticular, it was observed that different emulsion droplets displayedvarious adsorption-coalescence phenomena on the prepared membranes,and a mechanism of selective demulsification was further proposed.These results suggest that the fabrication strategy is beneficialto fabricating membranes with outstanding separation efficiency.