| In recent years,frequent oil spill and chemical leakage have caused serious environmental pollution and waste of non-renewable resources,posing a great threat to the sustainable development of human beings.How to treat oily wastewater efficiently in an environmentally friendly way has become an urgent problem to be solved,which has attracted extensive attention from scholars all over the world.The common treatment methods of oily wastewater mainly include flotation,physical adsorption,chemical decomposition,in-situ combustion,biodegradation and so on.Among them,physical adsorption materials have broad application prospects in the field of oil/water separation because of environmental friendly,high separation efficiency,low cost,recycling,oil can be recovered and other advantages.Polymer-based three-dimensional porous materials with special wettability have shown excellent oil/water separation ability as oil adsorbents by virtue of their characteristics of low density,large porosity,high specific surface area,connected pore structure,hydrophobic and lipophilic etc.,and have become one of the research hotspots in the field of oil/water separation materials.However,the low hydrophobicity and high brittleness of polymer based 3D porous materials often restrict the separation efficiency and service life.Therefore,this paper aims to develop polymer-based porous composites with excellent super-hydrophobicity,elasticity and oil/water separation performance to achieve efficient and selective separation of oil-contaminated water.Firstly,thermoplastic polyurethane(TPU)was used as the raw material of flexible porous matrix,and carboxylated multi-walled carbon nanotubes(cMWNTs)were used as nano fillers(0.5-3 wt%).The super-hydrophobic TPU/cMWNTs porous composites with three-dimensional hierarchical porous structure were prepared by thermally induced phase separation(TIPS)method.Then,the microstructure,compressive mechanical properties and oil/water separation properties of the materials were characterized and analyzed by scanning electron microscope,fourier transform infrared spectrometer,automatic mercury injection apparatus,contact angle tester and universal testing machine.The results are as follows:(1)The microstructure analysis of the composites shows that cMWNTs are completely coated in the porous TPU skeleton and dispersed uniformly.Using the supporting effect of cMWNTs on the porous skeleton,the porous structure of the composites can be regulated by changing the content of nano-fillers.When the content of cMWNTs is 2wt%(TPU/cMWNTs-2),the porous composites have the best hierarchical porous structure.(2)Compared with pure TPU monolith,the water contact angle(151°)and saturated adsorption capacity(6.9-42.3 g g-1)of TPU/cMWNTs-2 porous composites were significantly increased.(3)The TPU/cMWNTs-2 porous composite exhibits excellent reversible compressibility and fatigue resistance during 1000 cycles of compression,so it can be quickly reused and oil recovery by adsorption-squeezing method.(4)TPU/cMWNTs-2 porous composites can maintain excellent hydrophobicity and oil adsorption capacity under different p H values(1-14)and high/low temperature(0-100?)conditions,showing good environmental adaptability.Subsequently,in order to further improve the comprehensive properties of TPU-based porous composites,reduced graphene oxide(RGO)was selected as nano-filler(0.5-2 wt%)to prepare super-hydrophobic TPU/RGO porous composites with hierarchical structure,and the microstructure and properties of the composites were studied in detail.The results show that:(1)When the content of RGO is 1.5wt%(TPU/RGO-1.5%),the porous structure of the composite is the most uniform,and the average pore size(50?m)and porosity(87.1%)are the largest.(2)The water contact angle of TPU/RGO-1.5%porous composite is 155°,the oil contact angle is 0°,showing excellent super-hydrophobic/super-oleophilic properties,and can be used for efficient selective separation of oil/water mixture.(3)The compressive strength of TPU/RGO-1.5%porous composites is 307 k Pa,which is about 98%higher than that of pure TPU monolith.Under the condition of large strain(80%)cyclic compression(1000 cycles),it exhibits excellent reversible compressibility and fatigue resistance.(4)The oil/water separation performance of TPU/RGO-1.5%porous composite is stable in strong acid and alkali,high/low temperature and liquid disturbance environment,showing excellent environmental adaptability.(5)Using pump-assisted adsorption device,TPU/RGO-1.5%porous composite can achieve continuous and rapid selective separation of oils/organic solvents on the water surface,the separation efficiency is up to 98%,and the continuous oil adsorption capacity can reach at least15000 times its own weight. |
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