Preparation Of Superhydrophobic Elastic SiO₂/Polyurethane Sponges And Their Adsorption And Regeneration Performance In Oily Wastewater

80 percent of China’s auto repair shops are small in scale,low in technology,widely distributed,and some are even established in residential areas or other sensitive areas.limited by their own conditions,most of the oily wastewater is discharged into public sewers or the surrounding environment without proper treatment.It has become an environmental pollution that needs to be solved urgently.Hydrophobic Si O₂aerogels with water glass as precursor is simple and inexpensive to prepare,and with high porosity,and oleophilic.It’s an ideal adsorbent for fast and efficient treatment of oily wastewater from auto repair.However,the low mechanical strength and fragility of conventional hydrophobic Si O₂ aerogels greatly limit the practical application in the field of oil-water separation.Therefore,in this study,superhydrophobic Si O₂ aerogels（SA）and elastic superhydrophobic Si O₂/polyurethane sponges（SA/PUS）were prepared by sol-gel method at room temperature and pressure using inexpensive industrial water glass,commercial polyurethane sponge（PUS）and trimethylchlorosilane（TMCS）as precursors,skeleton and hydrophobic modifier.The SA/PUS overcomes the deficiency of low mechanical strength of traditional hydrophobic Si O₂ aerogels and expands the application scope of Si O₂ aerogels.The microscopic morphology and structure of the materials were also characterized by X-ray diffraction analysis（XRD）,Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,contact angle measurement,specific surface area and porosity analysis（BET）,and thermogravimetric-differential thermal analysis（TG）.The adsorption mechanisms and factors influencing the adsorption of suspended oil and oil-in-water emulsions by SA and SA/PUS were investigated.The main research findings are as follows:（1）For SA/PUS,the preparation conditions were optimized by orthogonal experimental method,and the optimal preparation conditions were as follows:the pretreatment time of PUS is 8 h,the p H value of adhesive formation is 3.0,the aging time is 24 h,and the amount of TMCS modifier is 50 m L.In this condition,the water contact angle of SA/PUS is 158.5°.It is a superhydrophobic material with simple preparation process and low cost,which is suitable for the treatment of oily wastewater in auto repair enterprises.（2）SEM results show that the surface particles of SA after hydrophobic modification are rough and fluffy in structure,with the typical microsurface of hydrophobic materials.SA has a specific surface area of 460.31 m²/g and an average pore size of 6.50 nm.While the surface of SA/PUS is covered by a layer of Si O₂ nanoparticles and retains the three-dimensional network structure of PUS,with a specific surface area of 686.10 m²/g.SA/PUS can withstand up to 61.90%of compressive strain and quickly recover the original shape after stress release,and its compressive strength only decreased by 13%after five fatigue cycles of compression,which is in contrast to the low strength and high brittleness of SA,making SA/PUS more effective in the treatment process of oily wastewater is more convenient to recover and improve efficiency.（3）The hydrophobic group-CH₃ on the surface of Si O₂ aerogels makes both SA and SA/PUS have excellent adsorption performance on oil-in-water emulsions:the adsorption capacity of SA and SA/PUS on emulsified oil can reach up to941.32 mg/g and 1068.46 mg/g,respectively.Due to the electrostatic adsorption,the adsorption capacity decreases with the increase of p H.The best adsorption effect is achieved when the solution p H is 3.（4）Although SA has good adsorption capacity for oil-in-water emulsion,SA is in the form of powder with low mechanical strength and fragile,and in the process of adsorption of suspended oil in water,agglomeration is very likely to occur,which makes it difficult to recover.On the contrary,SA/PUS is in the form of block,which improves the mechanical strength of SA and has good separation capacity for suspended oil in water,and its adsorption capacity can reach 11190.36mg/g.The oil adsorbed on SA/PUS can be recovered by external extrusion,and the oil recovery efficiency can reach up to 92.70%.Even after 10 adsorption-desorption cycles,the oil recovery efficiency can still reach 89.86%.SA/PUS expands the application scope of SA and shows great potential in oil-water separation and recycling.