淡江大學機構典藏:Item 987654321/34770
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    Title: 蛋白質/多醣體混合物之掃流微過濾
    Other Titles: Cross-flow microfiltration of protein/polysaccharide mixture
    Authors: 司盼妤;Sz, Pan-yu
    Contributors: 淡江大學化學工程與材料工程學系碩士班
    黃國楨;Hwang, Kuo-jen
    Keywords: 微過濾;掃流過濾;生化分離;薄膜結垢;薄膜分離;microfiltration;Cross-flow filtration;bio-separation;Membrane fouling;Membrane separation
    Date: 2009
    Issue Date: 2010-01-11 05:35:39 (UTC+8)
    Abstract: 本研究以平板式掃流微過濾探討多醣體與蛋白質之分離純化。以孔徑0.025 micrometer之醋酸纖維濾膜,在pH=7下,過濾分子量為67 kDa的牛血清蛋白(BSA)與2000 kDa之葡聚醣(Dextran),探討在不同的掃流速度與過濾壓差下,過濾速度、過濾阻力、物質的阻擋率與薄膜結垢情形。
    研究結果顯示,過濾牛血清蛋白與葡聚醣雙成分懸浮液時,掃流速度愈大,濾速也會愈快。增加過濾壓差時,濾速會上升,但過濾阻力也會顯著增加。牛血清蛋白與葡聚醣會在膜面上形成可逆及不可逆的結垢層,這些結垢層即為過濾時的主要阻力來源。利用共軛焦掃描式雷射顯微鏡(CSLM)觀察濾膜中的結垢情形,發現牛血清蛋白較葡聚醣容易吸附在膜面上,提高過濾壓差則會增加牛血清蛋白在膜面的吸附量,而此結果也與傅氏紅外線吸收光諎儀(FTIR)所分析出來的膜面結垢物成分相同。以HPLC分析濾液中各成分之含量,發現牛血清蛋白與葡聚醣之阻擋率皆會隨著掃流速度的上升而增加,而隨著過濾壓差增加,牛血清蛋白之阻擋率會上升,葡聚醣則是隨之下降。若操作在低掃流速度、高過濾壓差的條件下,葡聚醣的回收率可達70 %,而牛血清蛋白則為15 %,顯示此過濾程序能夠獲得良好的選擇率,達到分離、濃縮雙成分物質的目的。量測實驗後濾膜表面之平均孔徑,在不同的過濾壓差下,其變化量很小,而由理論所估算出來之平均孔徑,則會隨著過濾壓差的升高有變小的趨勢,這表示薄膜結垢的型態主要是縮小膜孔。以所推導的理論分析薄膜結垢,發現可將通過結垢層壓為43 kPa時差視為一分界點,大於此壓力時的結垢層較薄,反之則較厚,且其厚度不會隨著過濾壓差而改變。以此分界點推算出濾液流向的臨界雷諾數為1.75×10-5,在大於此臨界雷諾數的操作條件下,會使具有可變形的葡聚醣分子產生拉伸行為,使之較易通過膜孔道,故其穿透率增加,但球形的牛血清蛋白則較不易受到流體流態的影響,所以阻擋率會隨著過濾壓差的上升而增加。
    The separation and purification of polysaccharide/protein mixture using two-parallel-plate cross-flow microfiltration are studies. A binary suspension prepared by bovine serum albumin (BSA) with a molecular weight of 67 kDa and dextran with a molecular weight of 2000 kDa is filtered using a 0.025 micrometer cellulose acetate membrane. The effects of operating conditions, such as cross-flow velocity and filtration pressure, on the filtration flux, filtration resistance, molecular rejections and membrane fouling are discussed.
    The results show that an increase in cross-flow velocity or filtration pressure leads to higher flux. The reversible and irreversible fouling layers on the membrane surface formed by BSA and dextran molecular adsorptions are the main filtration resistance sources. The results of CSLM and FTIR analyses indicate that BSA is the major foulant adsorbed on the membrane surface. The BSA adsorption increases with increasing filtration pressure. The concentrations of BSA and dextran in the filtrate are measured using HPLC. The results show that both BSA and dextran rejections increase with increasing cross-flow velocity. However, BSA rejection increases but dextran rejection contrarily decreases with increasing filtration pressure. An optimal condition can be achieved by operating at low cross-flow velocity and high filtration pressure. The dextran recovery is as high as 70%, but BSA recovery is only 15% in such conditions. The membrane surface pore sizes are measured before and after experiments using SEM and image analyses. The results indicate that the membrane fouling is mainly caused by pore size reduction. However, the effect of filtration pressure on the mean pore size is trivial. The mean pore sizes under various conditions are also estimated using a model derived based on hydrodynamics. The calculated mean pore size decreases with increasing filtration pressure. According to the proposed model, the critical pressure drop through the fouled membrane is found as 43 kPa. When the pressure drop is lower than 43 kPa, the fouled layer is thicker, and the thickness doesn’t vary with cross-flow velocity or pressure drop. In contrast, the fouled layer is thinner when the pressure drop exceeds the critical value. A critical Reynolds number in the filtration direction is determined as 1.75 × 10-5 from the critical pressure drop. When Reynolds number is higher than the critical value, the stretch (deformation) of dextran molecules leads them to be easier to penetrate through the membrane pores, as a result, to increase the molecular transmission. However, the morphology of BSA molecules is not affected by flow pattern since the low molecular weight and spherical shape. Therefore, the BSA rejection slightly increases with filtration pressure.
    Appears in Collections:[Graduate Institute & Department of Chemical and Materials Engineering] Thesis

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