Preparation And Properties Of Environment-Friendly Polyurethane Composite Fiber As Oil-Water Separation Membrane

With the rapid development of modern industry,the water pollution problems tend to be more serious.The oil pollution in water body is the most serious and common pollution,such as oil spills at sea,oil tanker and blowout accidents,sewage discharged from port operations,and oily wastewater produced by oil industry,catering and car washing industry.The traditional oil-water separation methods have high energy consumption,high cost,low efficiency,poor selectivity,and easily produce secondary pollution.At present,the research on superwetting separation membrane has been widely concerned,especially the superhydrophobic membrane materials show excellent separation performance.Most hydrophobic polymers used in superhydrophobic fiber membranes,such as polyamide（PA）,polyvinylidene difluoride（PVDF）,polytetrafluoroethylene（PTFE）,are not degradable and cause secondary pollution during the recycling process.Therefore,the exploring of sustainable,durable and superwetting composite fiber membrane for oil-water separation is one of the biggest challenges in the field of wastewater treatment.Polyurethane materials（PU）have good mechanical properties and stability.The PUs prepared by using biodegradable polymers with hydroxy-terminated and diisocyanate as reactants are expected to have good biocompatibility and environmental friendliness.The hydrophobic modification of prepared PU matrix as oil-water separation membrane material has not been reported so far.In this paper,polycaprolactone diols（PCL_d）and diisocyanate were used to prepare environment-friendly polyurethane material（bio-PU）.The superhydrophobic bio-PU based composite membranes as an efficient oil-water separation membrane were modified by adding different components for functional modification and adjusting the microstructure of bio-PU composite membranes.The oil-water separation performances and mechanisms were discussed in detail.This study had two parts:（1）The bio-PU was synthesized by introducing biodegradable PCL_dsegments.The superhydrophobic modified titanium carbide nanoparticle（TiC_P）by1H,1H,2H,2H-Perfluorodecyltrimethoxysilane（PFDTS）was dispersed on eletrospun bio-PU nanofiber matrix by ultrasound,so that the composite fiber membrane presented a hierarchical structure composed of nanofibers,microspheres and nanoparticles.The prepared bio-PU/TiC_Pcomposite fiber membrane displayed superhydrophobicity with WCA of 153.1±1.2°.Even for oil-water emulsion,the bio-PU/TiC_Pmembrane exhibited the outstanding separation efficiency（99.65%）and high flux(2464.79 L m^-2h^-1).Moreover,the bio-PU/TiC_Pmembrane also had the excellent self-cleaning,water repellency and recyclability.These characters endowed bio-PU/TiC_Pmembrane great potential application in sustainable oil-water separation.（2）In order to further expand the sustainable application of bio-PU in wastewater treatment,the bio-PU composite fibers as oil-water separation membrane with self-healing performance was prepared.The bio-PU24 was synthesized by isophorone diisocyanate（IPDI）and PCL_d.The bio-PU24 fiber membrane was prepared by electrospinning as substrate membrane,and the titanium carbide（TiC）modified titanium dioxide（TiC@TiO₂）and silica aerogel（Si O₂）were uniformly dispersed on the surface of bio-PU24 fiber membrane by ultrasound to obtain bio-PU24/Ti@Ti/Si-10 superhydrophobic composite membrane.The hierarchical structure of the composite membrane surface was formed by the introduction of different inorganic nanoparticles.The addition of Si O₂reduced the surface energy.Bio-PU24/Ti@Ti/Si-10 membrane showed superhydrophobicity with WCA of 158.3±0.7°.The separation flux and efficiency for oil-water emulsion were 2101.12 L m^-2h^-1and 99.1%,respectively.Because TiC@TiO₂endowed the composite membrane with photocatalytic performance,the bio-PU24/Ti@Ti/Si-10 membrane irradiated in the visible range had excellent self-healing performance and cycling stability.After 10emulsion cycles,the separation flux and efficiency of the membrane remained at2046.44 L m^-2h^-1and 99.08%.In addition,bio-PU24/Ti@Ti/Si-10 membrane also had good physical and chemical stability,water repellency and self-cleaning.