正滲透海水淡化程序的總能耗雖然理論上比逆滲透程序還大，但這篇論文已驗證:正滲透程序若使用溫敏型離子液體水溶液作為提取液，則可以較逆滲透程序節省電能耗。這個研究有三個目標，首先是提出設計提取溶質的策略，再來是示範基本評估溫敏型提取液的方法，最後則是最佳化使用溫敏型提取液的正滲透複合程序。
設計提取溶質時，首先要了解哪些關鍵性質主導著提取液在正滲透複合程序中的效能。本論文針對其中「在正滲透階段作為驅動力的提取液滲透壓」、「影響相分離階段熱能耗的相分離溫度」、以及「主導加壓產水階段作功能耗的富水相滲透壓」三個性質與離子液體材料的特性做深度研究。藉滲透壓分析的結果顯示，當「溶質與水的交互作用力參數χ_12」愈低，雖然提取液的滲透壓會提高，但其相變溫度也會提高，進而增加相分離程序之熱能耗；另外，當「溶質分子量除以凡特荷夫因子M_2/i_2的值」愈高，即便富水層溶液之滲透壓會降低，提取液之黏度也會隨之提高，進而限制正滲透程序的水通量。是故，此論文提出χ_12的最佳值大約在0.65，並建議未來的研究方向在於找到M_2/i_2的最佳區間，以完整提取溶質的設計策略。
本論文接著選擇[P_1][Mal]及[P_2][TMBS]_2此兩支低臨界溶液溫度在室溫左右的材料，進一步量測室溫巨觀分層後，富離子液體層及富水層之濃度。綜合相圖及兩相的滲透壓，即能評估材料是否能在室溫相變、分層後富離子液體相是否適合直接作提取液、以及由富水相取代海水進行加壓產水的程序是否較節能。
再者，藉由相圖、相分離機制的觀察、以及相分離階段熱能耗和加壓產水程序功能耗之仔細計算，一步一步鎖定讓正滲透複合程序省時又節能的最佳的初始條件—相分離槽最初的濃度。並運用質量守恆定理，計算出維持系統進出水量一致的操作條件—加壓產水程序的回復率。
最後，由於相分離階段熱能耗的計算結果本身就大於直接用逆滲透產水的能耗，所以再次證明正滲透程序整體能耗較大；然而數據也證明: 若相分離程序可運用環境或工業廢熱，以使用[P_2][TMBS]_2作為提取溶質為例，則正滲透程序之電能耗可以低至逆滲透程序電能耗之12.7%。
基於以上的研究，首先建議將溫敏型提取溶質的親疏水性量化的χ_12值設計在約0.65左右；若期望降低富水相之滲透壓，可以設計較高M_2/i_2值之溶質，但需留意提取液之黏度；所研發之新的溫敏型材料，可藉相圖及兩相滲透壓之量測作初步評估；基本性質合適的材料，可進一步藉光學顯微鏡觀察相變速率以及能耗的理論計算鎖定讓程序最省時節能的最佳初始條件。

While theoretically consuming more energy in total, forward osmosis (FO)-based desalination process may consume less electrical energy than a sole reverse osmosis (RO) process by using responsive draw solution. Hence, in this thesis, lower critical solution temperature (LCST)-type ionic liquid aqueous solution is studied as a thermo-responsive draw solution in a FO-based process. This study aims to formulate strategies that design the ionic liquid for this application, that evaluate the designed thermo-responsive draw solution, and that determine the optimal initial condition of the corresponding process, for lower time and energy costs.
While designing the ionic liquid, it is essential to know the optimal values of the interaction parameter χ_12 and molecular weight of solute divided by its van’t Hoff factor M_2 ⁄i_2 . Because lower χ_12 indicates not only higher osmotic pressure of draw solution π_DS as higher driving force in FO, but also higher phase-separation temperature T_PS, which implies higher heat consumption for phase separation. Moreover, higher M_2 ⁄i_2 suggests not only lower osmotic pressure of diluted draw solution π_(d-DS) or lower work consumption for producing water from it, but also higher viscosity of draw solution η_DS, which limits the water flux in FO. In this thesis, the optimal value of χ_12 is found to be about 0.65 while determining the optimal M_2 ⁄i_2 requires more efforts in the future.
When assessed as draw solute, among four LCST-type ionic liquid, [P_1][Mal] and [P_2][TMBS]_2 are chosen to be further investigated since their phase-separation temperatures could be near the room temperature, 25 ℃, over a relatively broad concentration range. Then, after macro-phase separation at the room temperature, their osmotic pressures of ionic-liquid-rich and water-rich solutions are evaluated as π_DS and π_(d-DS). As the strong driving force in FO, π_DS should be higher than 60 (atm); for low energy consumption of the FO-based process, π_(d-DS) should be lower than that of sea water, which is about 27.6 (atm).
After the basic evaluation, the optimal initial condition of the FO-based process—that is, the initial concentration of the solutions in the phase-separation batches C_(PS_i)—can be found through observation of kinetics of phase separation and calculations of heat and work consumptions of the process, as demonstrated in this thesis. Additionally, according to the calculations, it is proved again that while consuming more energy in total, FO-based process could be more electrically energy-efficient than a sole RO process if the required heat is provided with waste heat, especially when [P_2][TMBS]_2 is used as the draw solute.
In conclusion, this thesis has found the optimal χ_12 to design LCST-type draw solute, yet the optimal M_2 ⁄i_2 remains to be further investigated. Moreover, the required heat in such a process has to come from waste heat so that it could be more electrically energy-efficient than a sole RO process. Finally, this study demonstrates the methods of evaluating designed thermo-responsive draw solution, and finding the optimal initial condition of the FO-based process for the purposes of saving time and energy.

Abstract.........................................................I
摘要............................................................III
誌謝..............................................................V
Index............................................................VI
List of Tables..................................................VII
List of Figures................................................VIII
I. Introduction...................................................1
I-1 Mechanism of FO Process.......................................1
I-2 Required Characters of Draw Solution and Parameters of Draw Solute............................................................2
I-3 Responsive Draw Solution......................................4
I-4 FO-based Process that Uses LCST-type Thermo-responsive Draw Solution..........................................................5
I-5 LCST-type Ionic Liquid as Draw Solute.........................9
II. Methodology..................................................10
II-1 Measurement of Osmotic Pressure.............................11
II-2 Measurement of Phase Diagram................................16
II-3 Analysis of Osmotic Pressure................................18
II-4 Quantification of Concentrations of Ionic-Liquid-rich and Water-rich Solutions.............................................20
II-5 Analysis of Kinetics of Phase Separation....................21
II-6 Mass Balance in the Whole FO-based Process..................22
II-7 Calculation of Heat Consumption in the Phase-separation Stage .................................................................26
II-8 Calculation of Work Consumption in the Reverse Osmosis Stage .................................................................28
III. Materials...................................................31
IV. Results......................................................32
IV-1 Measurement of Osmotic Pressure.............................32
IV-2 Measurement of Phase Diagram................................34
IV-3 Osmotic Pressure Analysis...................................38
IV-4 Quantification of Concentrations of Ionic-Liquid-rich and Water-rich Solutions.............................................42
IV-5 Kinetics of Phase Separation................................47
IV-6 Mass Balance in the Whole FO-based Process..................51
IV-7 Calculation of Heat Consumption in the Phase-separation Stage .................................................................54
IV-8 Calculation of Work Consumption in the Reverse Osmosis Stage .................................................................59
V. Discussion....................................................62
V-1 Molecular Design of LCST-type Draw Solute....................62
V-2 A Basic SOP for Evaluation of Thermo-responsive Draw Solution .................................................................64
V-3 A SOP for Determining the Optimal Initial Condition, the
Initial Concentration of the Solutions in the Phase-separation Batches C_(PS_i), of the FO-based Process that Uses Thermo-responsive Draw Solution.........................................65
VI. Summary......................................................67
VII. Reference...................................................69

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