薄膜性質對蛋白質多醣體混合液之掃流微過濾性能的影響

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Title:	薄膜性質對蛋白質多醣體混合液之掃流微過濾性能的影響
Other Titles:	Effects of membrane properties on the performance of cross-flow microfiltration of protein/polysaccharide mixtures
Authors:	江元君;Chiang, Yuan-Chun
Contributors:	淡江大學化學工程與材料工程學系碩士班黃國楨
Keywords:	微過濾;掃流過濾;薄膜結垢;蛋白質;多醣體;microfiltration;Cross-flow filtration;BSA;Dextran Membrane fouling;Membrane separation
Date:	2011
Issue Date:	2011-12-28 18:49:50 (UTC+8)
Abstract:	本論文旨在探討膜材結構對多醣體與蛋白質混合液之掃流微過濾的影響。分別使用孔徑為0.1μm之聚二氟乙烯膜(PVDF)、醋酸纖維膜(MCE)及聚碳酸酯膜(PC)作為濾材，對分子量為67 kDa之牛血清蛋白(BSA)與分子量為200 kDa之葡聚醣進行掃流微過濾，探討不同進料成分、掃流速度、過濾壓差以及膜材性質對濾速變化、擬穩態濾速、過濾阻力、各物質之分離效能以及薄膜結垢之影響。由研究結果得知，過濾牛血清蛋白或葡聚醣之單成分時，使用PC膜皆能獲得最高濾速。過濾牛血清蛋白/葡聚醣之混合液時，使用MCE膜與PC膜時，濾速會隨著壓力與掃流速度之增加而上升，使用PVDF膜時，濾速會隨掃流速度之增加而上升，但會隨壓力之增加先上升而後下降。利用掃描式電子顯微鏡(SEM)觀察各種薄膜之結垢和阻塞情形，發現MCE膜與PVDF膜主要的過濾阻力來源為孔道內阻塞、膜孔縮小以及膜面上結垢層的形成；而PC膜主要以膜面上結垢層的形成和膜孔縮小為主要因素。另以共軛焦電子顯微鏡(CLSM)觀察牛血清蛋白與葡聚醣在濾膜中之結垢分佈，發現在PVDF膜以及MCE膜表面之結垢以牛血清蛋白為主；而在孔道內之吸附方面，MCE膜以葡聚醣居多，PVDF膜則以牛血清蛋白較多。利用液相層析儀(HPLC)分析濾液中牛血清蛋白及葡聚醣之含量以了解各薄膜之分離效能，發現三種膜之葡聚醣穿透率皆隨著壓力之增加而增加，牛血清蛋白則反而下降。而掃流速度增加，葡聚醣與牛血清蛋白之穿透率都隨之下降。若欲將BSA及Dextran分開，則可使用PC薄膜，操作在掃流速度0.3 m/s、過濾壓差 100 kPa下，兩者穿透率差異達約50%。而若是欲在濾液中同時獲得較多的BSA及Dextran，則可使用PVDF薄膜，操作在掃流速度0.1 m/s、壓力20 kPa，兩者之穿透率皆在70%以上。量測實驗後之薄膜孔徑，理論值與實驗值皆隨著壓力增加而下降。利用理論值計算膜結垢層之深度與厚度，發現壓力增加時，前者隨之減少；後者隨之增加。 The effects of membrane structures on the separation of polysaccharide/protein mixtures using cross-flow microfiltration are studied. The suspensions are prepared using bovine serum albumin (BSA) and dextran. Their molecular weights are 67 kDa and 2000 kDa, respectively. Three 0.01 μm membranes made of mixed cellulose ester (MCE), polyvinylidene fluoride (PVDF) and polycarbonate (PC) are used as the filter media. The effects of cross-flow velocity, filtration pressure, components of feed and structure of membrane on the filtration flux, filtration resistance, separation efficacy and membrane fouling are discussed. When sole BSA or dextran is filtered, the use of PC membrane always results in the highest flux compared to those of the other membranes. When BSA/dextran mixtures are filtered, the filtration flux increases with increasing cross-flow velocity for all membranes due to less membrane fouling. An increase in filtration pressure leads to higher flux for all membranes because of higher filtration driving force. However, a contrary effect is found under high pressures when PVDF is used due to the unexpected increase in fouling resistance. The results of SEM analyses indicate that the fouling types of MCE and PVDF membranes include pore blocking, fouling layer on the membrane surface and pore size reduction, but no pore blocking can be observed for PC membrane. The results of CLSM reveal that the fouling on the membrane surface is mainly caused by the deposition of BSA for MCE and PVDF membranes. The fouling occurred in membrane pores is mostly due to dextran adsorption for MCE membrane while due to BSA adsorption for PVDF membrane. The concentrations of BSA and dextran in the filtrate are measured using HPLC. Both BSA and dextran transmissions decrease with increasing cross-flow velocity because of the sweeping effect on the membrane surface. An increase in filtration pressure leads to lower BSA transmission but higher dextran transmission for using all membranes. Using PC membrane and selecting u = 0.3 m/s and ΔP = 100 kPa is the optimum condition for the separation of BSA and dextran since their transmission difference is as high as 50%. If both BSA and dextran are desired products, the transmissions of BSA and dextran are higher than 70% by using PVDF membrane and operating at u = 0.1 m/s. The Experimental and theoretical values of the mean pore size of fouled membranes decrease with increasing filtration pressure. The calculated fouled layer depth decreases but the fouled thickness in the membrane pores increases with increasing filtration pressure.
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