Study On Preparation Of PES Hollow Fiber Nanofiltration Membrane And Its Separation Performance

Nanofiltration membrane plays an important role in sewage treatment and reuse and deep purification of drinking water.The traditional hollow fiber nanofiltration membrane often uses polyether sulfone（PES）ultrafiltration membrane as the base membrane to prepare polyaromatic amide nanofiltration membrane layer by interfacial polymerization method.However,due to the poor hydrophilicity of PES hollow fiber wipes membrane,it has a bad effect on the separation performance of nanofiltration membrane formed.In this thesis,the modifier Twain 80 was added to PES casting liquid to improve the preparation of PES hollow fiber ultrafiltration membrane hydrophilicity and interception ability,and to the modified ultrafiltration membrane as the base membrane,through the interface polymerization method and physical deposition method prepared three types of PES hollow fiber nanofiltration membrane,investigated the water purification capacity of different types of nanofiltration membrane,in order to provide reference for related research.In this thesis,PES hollow fiber ultrafiltration membrane was prepared by dry-wet spinning method,and the influence of the amount of Tween 80 in the casting solution on the hydrophilicity and interception ability of ultrafiltration membrane was investigated.The experiment shows that:When PES concentration was 19 wt%,Tween-80 concentration was 9wt%,PEG-400 concentration was 5 wt%,PVP concentration was 4 wt%and DMAC concentration was 62 wt%,the performance of the ultrafiltration membrane prepared under this formula was the best.At 1 bar,the maximum water flux could reach 234.8 L/（m²Â·h）.The water contact Angle reached 62.87°,the hydrophilicity was improved,and the Congo red and BSA had high interception performance.In this thesis,the optimal ultrafiltration membrane as the base membrane,respectively in its inner and outer surface through the interfacial polymerization method to obtain two PES hollow fiber nanofiltration membrane,and explore the preparation of internal and external pressure nanofiltration membrane,monomer concentration of water phase and organic phase,interfacial polymerization reaction time,heat treatment conditions on the preparation of nanofiltration membrane.The internal and external pressure nanofiltration membranes prepared were characterized by FT-IR,scanning electron microscopy and other characterization methods.The water filtration flux,the ability to detain dyes and inorganic salts,and the anti-pollution ability of the two nanofiltration membranes were investigated.The results showed that:When the operating pressure was 5 bar,the water flux of internal pressure nanofiltration membrane was 43.65 L/（m²Â·h）,and that of external pressure nanofiltration membrane was 35.48 L/（m²Â·h）.The water flux attenuation rates of internal pressure nanofiltration membrane and external pressure nanofiltration membrane were 4.9%and 11.7%,respectively.The flux recovery rates of the internal pressure and external pressure nanofiltration membranes were 96.1%and 90.6%,respectively.The interception rates of the internal pressure and external pressure nanofiltration membranes for Congo red,chrome black T,Victoria Blue B and methyl blue could reach more than 90%.For inorganic salt,the interception law was as follows（R）:Na₂SO₄>Mg SO₄>Mg Cl₂>Na Cl,and the retention effect and water permeability of the prepared internal pressure nanofiltration membrane were better than those of the external pressure nanofiltration membrane.Finally,the quaternary ammonium oxide（QGO）nanosheet material was deposited inside the modified PES hollow fiber ultrafiltration membrane by means of high-speed cross-flow circulation,and the quaternary ammonium oxide composite nanofiltration membrane was prepared.The QGO and QGO composite nanofiltration membranes were characterized by infrared characterization,XPS and scanning electron microscopy,and the properties of QGO composite nanofiltration membranes were tested.The results show that the water flux of QGO composite membrane is 169.3 L/（m²Â·h）under the operating pressure of 5 bar.The adsorption of HA,EBT,VBB,MB and CR by QGO nanofiltration membrane can reach more than 90%,and the water flux attenuation rate is 3%.In addition,the antibacterial test of QGO composite nanofiltration membrane was carried out,and the bacteriostatic rate of QGO membrane reached87.6%,which was because the quaternary ammonium salt group on the surface of QGO would destroy the bacteria and inhibit the growth of bacteria.Moreover,QGO has good hydrophilic surface,which can form a hydration layer and inhibit bacterial reproduction on the membrane surface.