| As a green and energy-efficient separation technology, ultrafiltration has been widely applied in various fields. However, membrane fouling occurs not only shorted the service life, but also restricted largely the development of ultrafiltration membranes. Major approaches, such as developing novel hydrophilic membrane and hydrophilic modification of membrane have been carried out for fouling reduction. Based on the change of pore structure and surface hydrophilicity of ultrafiltration membrane, cellulose acetate(CA) was selected to prepare ulreafiltration membrane for the aim of reducing membrane fouling.The concrete content is as follows:Firstly, the influence on fiber quality of modified solvent method and the synthesis of cellulose acetate were discussed. Orthogonal experiment was designed to extract cellulose from sugarcane bagasse by using the improved method of high boiling solvent, and then CA was prepared through the two-step approach. The test results showed that the optimal scheme of cellulose extraction: 80% of solvent concentration, 1:12 of solid-liquid ratio, 5.5 h of the reaction time.And the order of these factors on the experimental results: solvent concentration> solid-liquid ratio> reaction time. With the higher productivity of cellulose,the quality is better than that of the traditional acid and alkali preparation process. Tegree of substitution for synthesized CA was 2.8, which could be belonged to the scope of cellulose triacetate.Secondly, the effects of additives P123 on the performance of CA ultrafiltration membrane were explored. The results showed that modified membrane porosity increased with increasing levels of P123,while which didn`t work for improving the membrane surface hydrophilic,nor did the thermal stability of membrane. We can see clearly in the SEM figure that the modified ultrafiltration membrane not only formed the finger macroporous structure, also thin layer.But its mechanical performance fell slightly. When the addition amount of P123 was 25%, it exhibited relatively good separation performance, the pure water flux was 83.40L·m-2·h-1and the rejection of BSA was 69.37%. P123 acts as a porogen role in modifying the experiment.Thirdly, the effects of PVA/CA ratio in composite membrane material on performance of P123-CA-PVA composite ultrafiltration membranes were investigated. The results showed that PVA and CA is not a simple physical mixing, but the hydrogen bond crosslinked between each other,which improves the thermal stability of the membrane, enhanced elongation at break of the membrane. Increasing the amount of PVA can greatly improve the hydrophilic properties of the membrane surface, while the membrane porosity within a predetermined range slightly improved. SEM figure shows the presence of large number of holes in the modified membrane surface, which the water flux was improved by. But the BSA retention rate is not very satisfactory. When the PVA / CA = 1/5, the modified membranes possess the relatively better performance.Finally, the effects of the dosage of P123 on the performance of composite ultrafiltration membrane were researched, when PVA / CA ratio was1/5. The results showed that the addition of P123 makes the porosity of membrane reduced, mechanical performance slightly improved, and thermal stability constanted, while greatly improved membrane surface hydrophilic properties. The cross-sectional SEM image showed film with porous membrane surface and the large diameter hole finger support layer.Pore structure permeability enhancement and separation performance was improved. When PVA / CA ratio was1/5, P123 dosage was 20wt%, P123-CA-PVA composite membrane separation performance was the best, the pure water flux at this time was 106.03L·m-2·h-1, BSA rejection was 88.66%. |
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