Construction And Oil/Water Separation Characteristics Of Multifunctional Porous TPU-Based Monoliths

With the rapid development of global industry,the demand for petroleum and chemical products in various countries is increasing,and the frequent occurrence of marine oil spills and organic chemical leakage incidents has caused extreme damage to the water resources and ecological environment on which mankind depends.Removing oil and industrial organic wastewater from polluted water quickly and conveniently is the fundamental method to solve water pollution.At present,common oily wastewater treatment methods mainly include flotation,curing agent,in-situ combustion,bioremediation,etc.However,most of the above methods are expensive,low efficiency,high energy consumption and can cause secondary pollution.Physical adsorption materials have become one of the research hotspots in the field of oil/water separation because of their environmental friendliness,high separation efficiency,low cost,simple operation,and recyclability.The polymer-based porous monolith is a new type of bulk material with a three-dimensional interconnected porous structure.Due to its high porosity,large specific surface area,hydrophobic and oleophilic characteristics,it exhibits excellent oil/water separation ability as an oil adsorbent.However,the adsorbed materials are not easy to collect and cannot adsorb high-viscosity crude oil,which greatly restricts its practical applications in oil/water separation field.Inspired by this conception,this article aims to develop a multifunctional polymer-based porous monolith by special functionality,overcoming the performance limitations in practical oil/water separation applications and expanding its application range.First,the thermoplastic polyurethane(TPU)porous monolith,as the flexible matrix of the three-dimensional porous oil adsorbent,was fabricated by the thermally induced phase separation method(TIPS).Then,based on the dip-coating method(polydopamine adhesion)and subsequent hydrophobic modification of fluorosilane(trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane,FAS),Fe₃O₄nanoparticles are used as the surface magnetic layer material,the magnetic superhydrophobic TPU/Fe₃O₄@FAS porous monolith was constructed,and the microstructure,magnetic properties and oil-water separation performance of the composite material were analyzed in detail.The results of the study are as follows:(1)The introduction of Fe₃O₄ nanoparticles endows TPU porous monolith with excellent magnetic properties.Under the action of an external magnetic field,the magnetic drive and rapid collection of oil adsorption materials can be achieved;(2)The magnetic TPU/Fe₃O₄@FAS porous monolith presents a three-dimensional connected hierarchical porous structure with a wide range of pore size distribution.Fe₃O₄nanoparticles are uniformly coated on the surface of the porous framework;(3)The water contact angle of the magnetic TPU/Fe₃O₄@FAS porous monolith is 153^o,and oil contact angle is 0^o,revealing superior superhydrophobic/superoleophilic properties,and it can selectively separate different low-viscosity oils/organic solvents and exhibit high saturated adsorption capacity(6.0-41.1 g g^-1);(4)The magnetic TPU/Fe₃O₄@FAS porous monolith still maintains good super-elasticity and fatigue resistance after cyclic compression 1000 times.It adopts simple extrusion to cyclically adsorb and recover oil/organic solvents,demonstrating excellent recycling performance(5)Thanks to the good mechanical properties of the sample,the pump-assisted adsorption device can be used to quickly and continuously selectively adsorb the floating oil and organic solvent on the water surface.Then,the pure TPU porous monolith was used as the flexible porous matrix,and the MXene(Ti₃C₂T_x)nanosheets with excellent photo-thermal conversion performance were used as the surface photo-thermal layer material to prepare the superhydrophobic TPU/MXene@FAS porous monolith with photo-thermal effect.The microstructure,photo-thermal conversion capability and solar-driven crude oil/water separation performance have been studied in depth.The research results show that:(1)TPU/MXene@FAS porous monolith has a three-dimensional connected hierarchical porous structure and high porosity(88%),with a water contact angle of 156^o and an oil contact angle of 0^o,exhibiting good oil/water separation selectivity;(2)UV-Vis-NIR absorption spectrum analysis results show that the TPU/MXene@FAS porous monolith has excellent full solar spectrum absorption capacity(light wavelength range 200-2500 nm),and the light absorption rate is as high as 96%;(3)The TPU/MXene@FAS porous monolith exhibits excellent photo-thermal conversion efficiency.Under simulated sunlight conditions(1.0k W/m²),the top surface of the material can be self-heated to 69.7?within 1 min,and the highest equilibrium temperature is 80.5?(5 min);(4)The TPU/MXene@FAS porous monolith can quickly adsorb high-viscosity crude oil via light irradiation,resulting from the composite porous monolith directly converts the absorbed sunlight into heat energy by virtue of its own photo-thermal conversion mechanism.The porous material rapidly heats up and transfers heat to the crude oil to reduce its viscosity,which significantly improves the fluidity and diffusion rate of crude oil in the porous structure.(5)With the aid of the pump-assisted continuous adsorption device,the crude oil adsorption rate is increased by 16.7 times compared with the non-light conditions,and the oil absorption flow rate reaches 352.36 kg m^-2h^-1,which can achieve high-efficiency and selective separation of high-viscosity crude oil.