Investigation Of The Performance Of Superhydrophobic Modified Sepiolite-coated Polyurethane Sponge For The Collection Of Oil From Water Surface

With the rapid development of oil production and the ocean transportation industry,a large amount of industrial oily wastewater and frequent oil spills have brought great threats to the ecological environment.It is urgent to develop a simple adsorbent material for the collection of oil and organic solvent from water surface.In recent years,superhydrophobic sponge has attracted wide attention due to its good elasticity,adsorption capacity and selectivity,and has a good application prospect in oil-water separation.Sepiolite is a natural clay mineral that is easily surface modified due to its own ion exchange capacity and a large amount of Mg-OH on the surface.In this study,octadecyltrimethylammonium bromide(OTAB)and octadecyltrichlorosilane(OTS)were used for organic modification and superhydrophobic modification of sepiolite respectively,preparing superhydrophobic sepiolite.One-step ultrasonic dip-coating process is used to coated the superhydrophobic modified sepiolite on the surface of the three-dimensional porous polyurethane(PU)sponge,so that the prepared composites have superhydrophobic properties,thereby achieving selective separation of oil from water surface.In this study,Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS)were used to characterize the chemical composition of the surface of sepiolite modified before and after.The contact angles of the composites with different loading ratios were text and the optimum loading ratios was determined.We used scanning electron microscopy(SEM)to observe the surface morphology of polyurethane sponges coated before and after.The effects of pH,salt solution and temperature on the hydrophobicity of the composites were analyzed.The oil absorption capacity and oil-water separation performance of the composite materials were tested.And the conclusions are as follows:(1)The FT-IR and XPS results confirmed that the sepiolite were modified with OTAB and OTS successfully.And the optimum loading ratios(19%)of superhydrophobic modified sepiolite was determined by water contact angle measurement.The corresponding composites has a water contact angle of 158±2.9°.(2)It can be seen from the SEM photograph that the original three-dimensional porous structure of the sponge was not destroyed during the ultrasonic dip-coating process,and the micro-nano rough structure was constructed on the surface of the sponge skeleton.The micro-nano rough structure combined with the low surface energy substance(OTS)on the surface of the sepiolite was required for the PU sponge to possess superhydrophobic property.(3)In the experiment of hydrophobic stability of composites,it was found that pH,salt solution and temperature have no obvious influence on the hydrophobicity of the composites,and its superhydrophobic property can be maintained for at least 24 hours.(4)In the wetting property and oil absorption capacity test,it is found that the composites have the characteristics of rapid oil absorption and complete hydrophobicity;And it has a high adsorption capacity and can absorb oil of 29 to 68 times of its own weight,the adsorption capacity is mainly affected by the density and viscosity of oils;Moreover,the composite can maintain a high adsorption capacity during 10 cycles.(5)Oil-water separation experiments show that the composites possess high oil-water selectivity and oil-water separation efficiency.The initial separation efficiency of the four oil-water mixtures was above 99.66%,and the residual oil content in the water after separation was also below 34 ppm.After 10 cycles,the separation efficiency was still higher than 99.45%,and the oil content was also below 55 ppm.However,after 10 cycles of oil-water separation,the contact angle of the composites decreased to 145.6°,losing its superhydrophobic property.