Preparation And Properties Of Polyarylether Composite Ultrafiltration Membranes

Shortage of clean water is becoming an increasingly serious problem with the discharge of the industrial wastewater and domestic sewage.Compared with traditional separation and purification technology,membrane separation technology is a kind of efficient and environmental-friendly strategy for wastewater treatment and seawater desalination.However,membrane separation technology faces many problems including low permeability,severe membrane fouling and high modification costs,which is mainly related to the chemical properties and structure of the membranes.In these works,a series of composite ultrafiltration membranes were prepared by using polyarylethersulfone as membrane matrix and functionalized multi-walled carbon nanotubes,sulfonated polyetheretherketone,and polymeric nanoparticles as hydrophilic additives.The chemical properties and structure of the membranes are effectively improved by these means,thereby achieving a significant increase in membrane permeability and antifouling properties.Multi-walled carbon nanotubes are often chosen as an additive to improve membrane permeability due to its hollow tubular structure,which is a good water transfer channel.But their severe agglomeration makes them difficult to uniformly disperse in the solvent and membrane matrix.First,the pure carbon nanotubes were functionalized by chemical grafting,and then the zwitterionic carbon nanotubes were introduced to membrane matrix as hydrophilic additives,which effectively increased the volume porosity and hydrophilicity of the membranes,thereby improving the membrane permeability and the antifouling properties.Among them,the composite membrane containing 0.2 wt%of zwitterionic carbon nanotubes exhibited the most excellent performance,including 306 L/(m2 h)of pure water flux,85%of the flux recovery rate,and 94.5%of rejection of bovine serum albumin.Considering the tedious of chemical modification,it is necessary to seek a simple and effective modification method.Environmentally friendly polydopamine and polyvinylpyrrolidone were used to coat carbon nanotubes,and polymer modified carbon nanotubes with good hydrophilicity and good dispersibility were prepared.The introduction of polymer-coated carbon nanotubes significantly improved the filtration performance of the composite membranes.Especially,the composite membranes incorporating 0.1 wt%polyvinylpyrrolidone-modified carbon nanotubes exhibited the best ultrafiltration performance,including 290 L/(m2 h)of pure water flux,96.4%of rejection of bovine serum albumin,and 95%of flux recovery.In order to solve the balance problem between hydrophilicity and mechanical stability in the modification of ultrafiltration membranes,the commercial polyetheretherketones were conduct to sulfonation treatment,and functionalized polysulfone with crosslinkable groups(tertiary amine)was synthesized.The sulfonated polyetheretherketone was blended with the crosslinkable polysulfone,and a suitable amount of crosslinker was added to the casting solution to prepare a series of composite ultrafiltration membranes.On the one hand,sulfonates can provide high hydrophilicity of the membrane,on the other hand,the crosslinkable groups can maintain good mechanical strength and dimensional stability of the membrane.Thus,the composite membrane with good hydrophilicity and stable mechanical properties was prepared.To further reduce the production costs,and optimize membrane performance,a more simple method have been developed to prepare composite membranes:polymeric nanoparticle reinforced composite membranes.When the two kinds of casting solutions containing oppositely charged polyelectrolytes were mixed together,the polyelectrolytes can self-assemble to polymeric nanoparticles driven by electrostatic interaction.The polymeric nanoparticles exhibit excellent dispersibility and can withstand a broad pH range(pH 1-11)and a relatively high temperature(80℃).The introduction of nanoparticles greatly improved the overall performance of the membranes.The highest pure water flux of the composite membranes reached 460 L/(m2 h),and more importantly,it also maintained a high rejection rate of bovine serum albumin(97.6%).The polymer nanoparticle-reinforced composite membranes have been further optimized both in the preparation method and the membrane performance,and are expected to be widely used in water treatment.