Studies On Preparation,modification And Properties Of Anti-fouling Ultrafiltration And Nanofiltration Membrane

Nowadays,membrane technology for water treatment occupies a more and more important position in refining and petrochemical industry,but there are some problems such as low hydrophilicity,oil pollution and lower water flux.Modification is an important method to enhance the performance of anti-oil pollution of membrane.In this study,membrane is fabricated and modified to enhance its performance of anti-oil pollution.?1?Firstly,polysulfone ultrafiltration?UF?membrane is fabricated by phase inversion method and then the influence of different mass fraction of polysulfone about water flux is optimizated.?2?Polypiperazine-amide composite nanofiltration?NF?membrane is fabricated by interfacial polymerization on the support of polysulfone ultrafiltration membrane.To optimize the fabrication condition,the influence of different time,pH of interfacial polymerization on the nanofiltration membrane properties which are water flux and rejection ratio are measured.?3?Then the membrane surface is modified by using TiO₂ on the optimal condition to enhance its anti-fouling properties and the influence on properties of modified membrance through water flux,permeability,rejection ratio or contact angle is assessed.?4?Finally,the oil-containing water is treated by UF and NF membranes to test their properties.The result shows that the water flux of polysulfone ultrafiltration membrane is in proportional to the pressure,and the permeability decreases with the increase of the concentration of polysulfone which indicates that the optimal fabrication condition is 15%mass fraction for polysulfone.The pure water flux of nanofiltration membrane decreases with the increase of the time or pH of interfacial polymerization and increases then decreases for rejection ratio which shows that the optimal conditions for interfacial polymerization are 4 minutes and pH with 11.Compared with the pristine membrane,the pure water flux of modified ultrafiltration and nanofiltration membrane decreases by40.66%and 12.92%,indicating the modified layer significantly increases the membrane resistance.However,the contact angle of the modified membrane decreases by 46.91%and 21.68%,which shows that the hydrophilic of the membrane is significantly enhanced.By testing water flux and rejection ratio of modified nanofiltration membrane,the optimal mass of TiO₂ is 0.03 grams with 80 square centimetres of membrane for modification.By filtering the lower and higher oil-containing water?500 mg/L?,a slight decrease of water flux is observed for the modified membrane with stable water flux of15.65%and 2.2 times higher than that of pristine membrane due to the hydrophilicity of the modified membrane surface.Furthermore,for nanofiltration membrane,petroleum and TOC of the filtered lower oil-containing water decrease by 99.79%and 96.63%as well as an obvious increase and stability of water flux for modified membrane of 22.8%higher than pristine membrane.Meanwhile,petroleum and TOC of the filtered higher oil-containing water decrease by 99.83%and 99.89%and a slight decrease of water flux is observed for the modified membrane with stable water flux of 66.1%higher than that of pristine membrane due to the hydrophilicity of the modified membrane surface.For UF/NF system,there is an ideal effect for oil-containing water to be treated and all the properties of modified membrane system are much better than pristine one.In short,this study provides an effective way for membrane fouling in oily wastewater treatment of membrane technology and has practical application value in oily wastewater treatment.