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Title: | 水溶兩相系統相平衡之研究 Phase Equilibrium of Aqueous Two-Phase Systems |
Authors: | Jhih-Jie Yang 楊智傑 |
Advisor: | 諶玉真(Yu-Jane Sheng) |
Keyword: | 水溶兩相系統, Aqueous Two-Phase Systems, |
Publication Year : | 2008 |
Degree: | 碩士 |
Abstract: | 本論文中,將利用耗散粒子動力學法(Dissipative Particle Dynamics,DPD)模擬水溶兩相系統(Aqueous Two-Phase Systems,ATPSs)之相行為,其中分為兩大部分進行探討,第一部份是改變水溶兩相系統的系統參數,討論何種因素會影響到水溶兩相系統形成;第二部份是探討在不同環境下的水溶兩相系統下,何種因素會影響到水溶兩相系統的萃取效率,以便得到最佳的分離效果。
第一部份探討將改變斥力參數、組成濃度以及組成鏈長的參數,當兩種高分子的相容性越差、濃度越大、分子鏈越長,都會使的系統趨向於相分離,形成水溶兩相系統(ATPS)。原因是因為相容性越差,高分子A和B不喜歡在一起,因此只好犧牲亂度來降低內能,而形成相分離。濃度越大,則混合均勻時,系統的內能也就越大,相同的必須犧牲亂度來降低自由能。另外,當分子鏈越長時,混合時之總排斥力正比於χN,所以當聚合度越大時(分子鏈越長時),總排斥力也會隨之增加,因此必須相分離來降低自由能。另外在邊界部分,水會在此區域形成緩衝區塊,以緩和高分子間的排斥力。所以當分子間排斥力越大時,緩衝區塊也就越明顯。 第二部份探討改變斥力參數、組成濃度、鏈長以及增加被萃取物分子鏈長,發現萃取效率與組成的濃度分佈有關,若上層高分子A的濃度和下層高分子A的濃度相差很大時,萃取效果也就會變好,所以改變上下層濃度差,才是改良萃取效率的好方法,因此ATPS的相圖是一個非常重要的指標。另外,當被萃取物的分子量變大時,同樣也可以使被萃取物的選擇性更明顯,所以萃取效率就會越佳。 Aqueous two-phase systems are prepared by combining two water-soluble polymers or a salt in water, above a critical concentration. These systems separate into two immiscible liquid phases, one of them enriched in one polymer and the other enriched in the other polymer or salt. Aqueous two-phase extraction method has been recognized as a nondenaturing and nondegrading technique of a number of biological entities such as proteins, enzymes, viruses, cells, and cell organelles. In this work, dissipative particle dynamics (DPD) is employed to investigate aqueous two-phase systems (ATPSs). The study can be divided into two parts. The first is the study of the effects the compatibility of two polymers, concentrations of two polymers and molecule length of two polymers on the formation of aqueous two-phase systems. The second is the extraction efficiency. We consider partition coefficient K as an index of the extraction efficiency, and vary the compatibility of two polymers, concentrations of two polymers, molecule length of two polymers and molecule length of the extractor in search of the best extraction efficiency. According to the simulation results, we observe that aqueous two-phase systems consist of three parts : polymer 1 – rich region, polymer 2 – rich region and boundary. As the incompatibility of two polymers, concentrations of two polymers and molecule length of two polymers increases, degree of phase separation becomes more obvious. Eventually, only negligible amounts of polymer 1 are found in the polymer 2 – rich phase and vice versa. In the boundary region, water forms a buffer zone to alleviate the repulsive interactions between polymers 1 and 2. Therefore, as the repulsion increases, the concentration of water increases. Simulation results also indicate that the partition coefficient (thus the extraction efficiency) is significantly affected by the degree of phase separation and therefore all the factors that have an effect on phase separation influence the extraction efficiency. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/26771 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 化學工程學系 |
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ntu-97-1.pdf Restricted Access | 2.66 MB | Adobe PDF |
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