Preparation And Characterization Of TiO₂/Polyamide Composite Reverse Osmosis Membrane

Human being can not survival without fresh water. As water shortage is gettingmore and more serious, it become one of the most important agendas of thegovernments around the world to resolve the water issue in agriculture, industry andliving consumption. Though one of the most widely used and well developed watertreatment technology, reverse osmosis （RO） processes remain relativelyenergy-intensive, non-selective, and fouling-prone, which restrict the reverseosmosis’s development. The research of new reverse osmosis membrane with specialperformance is very important to the RO technology. The advantages of inorganicparticle and organic membranes can be combined by assembling inorganic particleinto porous membranes. The hybrid membrane has been a new direction of ROmembrane. Titanium dioxide （TiO₂） has been applied to solve various problems aboutenvironment because of its photocatalysis and hydrophilic. Therefore we will addTiO₂into the aromatic polyamide thin film composite membrane to improvemembrane’s permeability and fouling-resistance. The hybrid membrane combineadvantages of particle and membrane.Two different methods were used to prepare anatase （TiO₂） and preliminarycondition of different methods was also explored. Synthetized TiO₂werecharacterized by scanning electron microscope（SEM）. SEM figure display TiO₂-Aparticals synthetized by method A is kind of spherical, and particle size is200nm;TiO₂-B particals synthetized by method B is mono-dispersed spherical, and particlesize is600nm. X-ray powder diffraction （XRD） confirmed synthetized TiO₂wasanatase; Dimension of TiO₂-A crystal was11nm and dimension of TiO₂-B crystal was9.9nm.The synthesized TiO₂-A and TiO₂-B were added into the aromatic polyamide thin film composite membrane respectively. The TiO₂-A dispersed into aqueous phaseand organic phase were added into the aromatic polyamide thin film compositemembrane respectively via interfacial polymerization of m-phenylenediamine （MPD）in the aqueous phase and trimesoylchloride （TMC） in the organic phase to improvethe water permeability. The hybrid membrane fabricated by dispersing TiO₂-A intoorganic phase has better permeate quality compared to that fabricated by dispersingTiO₂-A into aqueous phase. The performance of hybrid membrane fabricated bydispersing TiO₂-A into organic phase （0.03%,w/v） was the best (Water Flux40.8L.h^-1.m^-2，Salt Rejection98.3%). The surface and cross-section structure of hybridmembranes were characterized by SEM. SEM displayed that the surface of the hybridmembrane fabricated by dispersing TiO₂-A into aqueous phase appeared less structureof peaks and valleys, and paticles were visible in the finger-like pore. The surface ofthe hybrid membrane fabricated by dispersing TiO₂-A into organic phase appeared theapparent structure of peaks and valleys. And paticles were visible on the membranesurface. Energy dispersing spectra （EDS） analysis confirmed that TiO₂-A wassuccessfully incorporated into the membranes. The synthetized hybrid membranefabricated by dispersing TiO₂-B into organic phase （0.03%, w/v） has betterperformance (Water Flux36.6L.h^-1.m^-2, Salt Rejtction97.5%). SEM and EDS ofsynthetized hybrid membrane was familiar with the hybrid membrane（TiO₂-A）. Theresult is that membrane has better separation performance and membrane structure byadding TiO₂into the aromatic polyamide thin film composite membrane.The separation performance of the hybrid membranes was also tested underforward osmosis condition, the Water Flux of hybrid membranes was twice that ofcomposdit membrane. The anti-fouling of hybrid composite membranes wasinvestigated. The hybrid membrane verified a substantial prevention against themicrobial fouling.