Study On The Preparation, Structure And Performance Of PVA-Fe₃O₄ Hybrid Ultrafiltration Membrane

The principle and application of ultrafiltration(UF), the fouling of UF membrane and approaches of preventing membrane fouling, as well as the research progress of the poly(vinyl alcohol)(PVA) ultrafiltration membrane were introduced.PVA with good hydrophilicity is a potential excellent material in the preparation of anti-fouling UF membrane. The modification is necessary due to the properties of poor mechanical strength and swelling easily of pure PVA membrane. The PVA-Fe₃O₄ hybrid ultrafiltration membrane was prepared using PVA as the membrane material, Fe₃O₄ as filler, non-woven as base membrane, which has not been reported.PVA-Fe₃O₄ hybrid ultrafiltration membranes were prepared from a casting solution of PVA, water as solvent, acetic acid(HAC) as porogen, Fe₃O₄ as filler, boric acid(H3BO3) as cross-linking agent through the method of immersion precipitation phase inversion. The effects of the composite of casting solution and coagulation conditions on the membrane structure and performance were investigated. The permeated flux, rejection rate to BSA and anti-fouling property were investigated by ultrafiltration experiments. The cross-section and surface were observed by scanning electron microscopy(SEM). The tensile strength and elongation at break were tested by tensile testing machine. The contact angle was measured by contact angle apparatus. The total hot-water dissolving ratio was surveyed. The conclusions are as follows:The pure water flux increases while the rejection ratio decreases with the increasing of the content of Fe₃O₄. The cross-sectional pore size and porosity become greater. The mechanical properties first become better and after poorer. The anti-fouling property improved and the surface hydrophilicity enhanced. The flux basically unchanged when the content of Fe₃O₄ is more than 90wt%. The optimum content of Fe₃O₄ is 90wt%. The pure water flux decreases while the rejection ratio increases with the increasing of the concentration of PVA.The cross-sectional pore size and porosity reduced while the surface was denser. The mechanical properties become better. The anti-fouling property improved and the surface hydrophilicity enhanced. When the concentration of PVA is more than 12wt%, no water permeated through membrane. The BSA rejection ratio was more than 80% when the concentration of PVA is over 10wt%. The optimum concentration of PVA is 10wt%. The pure water flux increases while the rejection ratio decreases with the increasing of the content of HAC. The cross-sectional pore size and porosity increased while the surface was looser. The mechanical properties become poorer. The optimum content of HAC is 10mL. The pure water flux decreases while the rejection ratio increases with the increasing of the concentration of H3BO3. The mechanical properties become better. The surface hydrophilicity reduced. H3BO3 reduced the total hot-water dissolving ratio while improved the insolubility property of the membrane. The optimum concentration of H3BO3 is 1²wt%PVA.The membrane exhibited a good performance when using a solution of Na₂SO₄-KOH-H2O as coagulation bath. The pure water flux increases with coagulation temperature rising while decreases with coagulation time extension. The optimum content of Na₂SO₄, coagulation temperature and time is 50g/300mLH₂O, 25℃and 40min.