The Superhydrophobic Modification Of Porous Flexible Material And Its Application In Oil/Water Separation

The use of oil-absorbing materials for physical adsorption is currently the most widely used method of handling oil spills.In this paper,the process of chemical roughening followed by sol-gel method was proposed to modify the EPDM foam rubber and the modification effect was evaluated.The paper studied the effect of operating conditions on the superhydrophobic modification and determined the best modification conditions.Subsequently,the characterization was carried out to analyze the modification mechanism and the properties of oil/water selectivity,oil adsorption capacity and reusability were tested.Finally,the prepared EPDM-FR combined with specific device was used to recover oil from water surface.The results showed that the water contact angle of the superhydrophobic EPDM-FR increased from 105oto 142o.The results of the characterization by SEM,FT-IR and XPS indicated that the hydrolysis and polycondensation reaction of MTCS introduced the polysiloxane coating with low surface energy and 3D framework structure to the rubber surface,resulting in the properties of superhydrophobicity and superoleophilicity.The results showed that the best modification condition was chemical coarsening time of 4h,modification time of 60min,speed of 200rpm,MTCS concentration of 1.0vol.%,MTCS/distilled water ratio of 1:1,and solvent type of n-hexane.The modified EPDM-FR had a water contact angle of 156o,showing superhydrophobic property.The results showed that the superhydrophobic EPDM-FR showed excellent superhydrophobic/superlipophilic property and outstanding oil/water selectivity.The oil absorption capacity was 8-12 times its own quality both to low viscosity oil and high viscosity oil.The superhydrophobic EPDM-FR could still maintain the stability of the polysiloxane coating structure after compression cycle or ultrasonic treatment in organic solvent,showing excellent reusability and durability.After 100 cycles of compression,the modified sample recovered to its initial shape without any plastic deformation and the mechanical strength was over 30 times higher than the pristine sample,showing excellent flexibility,mechanical durability and mechanical strength.In the oil continuous recovery from water surface,the oil recovery capacity was improved 4 times after the modification.The modified sample could recover oil with the rate of 3.57L/(s·m~2)at 4kPa,showing a very high rate of oil recovery,which could be raised by increasing the driving pressure.No water was observed in the collected liquid with the measured moisture content of only 1060ppm,demonstrating high oil-water separation efficiency of up to 99.9%.Moreover,the superhydrophobic EPDM foam rubber has a higher critical hydrophobic pressure,leading to stronger water resistance and better adaptability to complicated practical oil pollution in water body.