Fabrication And Oil/water Separation Characteristics Of Flexible Porous TPU-based Monoliths

In recent years,frequently occurring oil spillage and organic chemical leakage events on a global scale,causing serious harm to the ecological environment and human health,how to remove and collect oil pollutants from polluted water efficiently and environmentally have become an urgent problem to be solved,have aroused extensive concern of government worldwide.The current treatment methods mainly include gravity deposition,flotation,adsorption,in-situ burning,dispersion,solidification,bioremediation,etc.Among them,physical absorption has great application potential in the field of oil/water separation due to environmental friendliness,simple operation,high efficiency and recyclable,etc.As an adsorption material,the polymer-based porous materials exhibit excellent oil/water separation performance because of its high porosity,large specific surface area,3D interconnected pore structure,etc.However,the brittleness of the material often leads to its recycling performance and service life is greatly restricted.In view of this,the purpose of this paper is to develop a flexible polymer-based porous material with excellent mechanical and oil/water separation properties,so as to overcome the performance constraints of the practice oil/water separation application of the porous monolith.Firstly,the flexible of high hydrophobic porous TPU monoliths were first prepared by thermally induced phase separation(TIPS)with the raw materials of thermoplastic polyurethane(TPU),the influence of fabrication parameters on the microstructure of the material was discussed.The microstructure,compression mechanics and oil/water separation performance of porous monolith were characterized in detail by scanning electron microscopy,mercury porosimetry,contact angle tester and universal testing machine,etc.The results are as follows:(1)When the polymer concentration is 8%(wt/v),phase separation temperature is 0?,phase separation time is 30 min,and the mixed solvent ratio is 9:1(v/v),the corresponding porous monolith shows a novel hollowed-out spherical hierarchical porous structure.At low magnification,it is mainly consisting of spherical voids(average diameter of?100?m)and connected pores(pore size of 30-50?m),at high-magnification,lots of smaller pores with nanoscale size(200-1000 nm)are observed on the three-dimensional skeleton with uniform distribution.The unique hierarchical porous structure not only increases the surface roughness,but also presents a wider pore size distribution;(2)TPU-8%porous monolith with water contact angle of 143~o and oil contact angle of 0~o,shows superior high hydrophobic and superoleophilicity,therefore,the TPU-8%monolith is capable to selectively absorb various oils/organic solvents from oil/water mixtures with saturated absorption capacity can reach to5.95-40.60 times for its own weight;(3)Super-elastic TPU-8%monolith exhibits remarkable large reversible compressibility and outstanding fatigue resistance under large strain(1500 cycles at 80%strain),allowing it to repetitively absorb oil/organic solvents via simple squeezing,shows excellent recycling performance;(4)The TPU-8%monolith has excellent chemical stability and environmental adaptability,the oil/water separation performance of the monolith is basically stable under different p H values(2-12),temperatures(0-100?)and extremely turbulent surface environment;(5)Based on the good mechanical properties of the material,it can also quickly and continuously absorb and remove oil/organic solvent from water surface by a pump-assisted filtration system.Subsequently,a certain concentration of carbon black dispersion was prepared,the porous TPU monoliths with different polymer concentrations were modified by simple dip-coating,further improve its comprehensive performance.The results show that:(1)CB@TPU-8%porous monolith presents a three-dimensional connected micro/nano hierarchical porous structure,with a water contact angle of up to 156~o and an oil contact angle of 0~o,realizing the transformation from high hydrophobic to superhydrophobic,the mechanical properties test shows that the compressive strength of the CB@TPU-8%monolith increased by 266%;(2)CB@TPU-8%monolith possesses excellent self-cleaning performance and oil/water separation ability,it can separate emulsion efficiently and quickly;(3)The CB@TPU-8%monolith has good superhydrophobic stability and chemical corrosion resistance in extreme environments.meanwhile,the addition of carbon black particles greatly improves the thermal stability of the monolith;(4)The cycle performance test shows that the CB@TPU-8%monolith has superior cyclic stability to various kinds of oils or organic solvents.