The Fabrication And Properties Of Underwater Superhydrophobic Oil/Water Separation Membrane

With the development of the society and the industry,the marine and coastal environment,aqueous ecosystems and the health of human beings was seriously threatened by the frequent oil spill accident and a large volume of oily waste water produced in our daily life and industrial production.An effective separation technologyof oil/water mixtures was urgently needed for oily wastewater remediation.The membrane separation technology was a high-efficiency and low-cost separation technology.Superhydrophilic and underwater superoleophobic oil/water separation membrane was a kind of new material,which can work into the water.The Superhydrophilic and underwater superoleophobic membrane can solve the problem of membrane fouling.Therefore,this underwater superoleophobic membrane can be used in oily wastewater,equipment of ocean transport,oil exploitation and oil spill accident.In this work,the polymers?chitosan,polyvinyl alcohol,cellulose,starch?was used as a surface hydrophilic coating material,SiO₂NPs as the surfaceroughnessmodifier,glutaraldehyde as the cross-linking agentand the nylon and stainless steel meshes as the substratesto fabricate the superhydrophilic and underwater superoleophobic membranes.The separation efficiencies of these membranes were examined.The main conclusions are as follows:?1?The chitosan-silica membrane was fabricated by chitosan and SiO₂NPs coated the nylon and stainless steel meshes,which was superhydrophilic and underwater superoleophobic.The optimum was examined in this work.The CAs of the CS stainless steel meshes and nylon fabrics changed from hydrophophobic to superhydrophibic?CA=0^o?,which can reach superhydrophilicity.Meanwhile,the underwater OCAs of the modified membranes can be above 150^o,which has increased43.5^oand 43.4^ofor CS stainless steel meshes and nylon fabrics,respectively.The maximum separation efficiency for CS stainless steel meshes and nylon fabrics can reach 99.4%and 99.6%,respectively.After 40 cycles,the separation efficiency can still reach above 95%.This chitosan-silica membrane can be used to hexane,cyclohexane,petroleum ether,diesel,soybean oil,lubricating oil and silicone oil.The flux of the CS coated nylon fabric could reach 44161 L^-1m^-2h^-1bar^-1.?2?Nylon and stainless steel mesh were used as substrates to prepare the PVA-SiO₂NPs underwater superoleophobic oil-water separation membrane.PVA 1788 coated membrane got a higher contact angle.The CAs of the PVA-SiO₂modified nylon and stainless steel meshes changed from hydrophobicity to superhydrophilicity?CA=0^o?.Meanwhile,the underwater OCAs of the modified nylon and stainless steel meshes couldreach 155.0^o and 156.6^o.The underwater OCAs of stainless steel meshes decreased to 152.8^o,151.5^o and 151.2^o in pH 4,7 and 10,respectively.after48 h.Though the underwater OCA decreased slightly,all of the immersed PVA-SiO₂coated meshes still exhibited underwater superoleophobicity.The maximum separation efficiency ofthe modified membranes could reach 99.4%,99.3%,99.4%,99.6%,99.0%,98.6%and 98.0%,for hexane,cyclohexane,petroleum ether,diesel,soybean oil,lubricating oil and silicone oil,respectively.After 80 cycles,the separation efficiency could still reach above 95%.The flux of the PVA-SiO₂NPs coated mesh and nylon fabric could reach 9523 L^-11 m^-2h^-1bar^-1and 6794 L^-11 m^-2h^-1bar^-1.?3?Nano-cellulose coated nylon and stainless steel mesh were superhydrophilic and underwater superoleophobic.Nano-starch had an excellentadhesive ability,but it didn't change the wettability of the surface of nylon and stainless steel mesh.Nano-cellulose got a better coating on the nylon surface.The nano-cellulose coated nylon has a high contact angle,it can reach 157.7^o.The maximum separation efficiencycan reach 99.8%.But after 5 cycles,the separation efficiency decrease a lot.The durability need to improve.?4?A durable and high-flux superhydrophilic-underwater superoleophobic oil-water separation membrane were prepared for effective oil-water separation by cellulose-starch-silica surface charging and hydrophilization.The water contact angles of the modified nylon and stainless steel mesh membrane attained 0^o,and underwater oil contact angles reached up to 159.5^o and 157.1^o,respectively.This membrane also exhibited durable underwater superoleophobicity in harsh environment?pH value 4 to 10?.The maximum separation efficiencies of the CSS coated nylon fabric for hexane,cyclohexane,petroleum ether,diesel,soybean oil,lubricating oil and silicone oilcould reach 99.9%,99.8%,99.5%,99.6%,99.4%,99.1%and 98.9%,respectively.And after 100 cycles,the separation efficiency of the modified meshes declined to 97.0%.The flux of the CSS coated nylon fabric could reach 31847 L^-1m^-2h^-1bar^-1.?5?With the comparison of the membranes,the CSS coated nylon fabric had the best separation efficiency,and theCS coated nylon fabric had the highest flux.The cost analysis showed that the PVA-SiO₂ coated nylon fabric had the lowest manufacturing cost,and the CSS coated nylon fabric had the highest profit.