臺灣博碩士論文加值系統

近年來由於能源與水資源匱乏的危機，具有高能源使用效率的脫鹽技術受到矚目並廣泛被研究討論。其中，電容去離子技術 (capacitive deionization, CDI) 為一低能耗、高產水率以及對環境友善的脫鹽技術。其操作係由被外加電場極化的電極吸附反向電荷離子並使離子由電雙層型態儲存於多孔電極表面，進而達到將水中離子去除的效果。電極的再生是藉由外部電場的移除或反向施加，吸附飽和的電極將離子釋出，同時產生高濃度的溶液。電容去離子系統的操作模式與電容去離子模組整體能耗有直接相關性，因此大量研究著重於電容去離子模組操作模式的改善，例如定電壓與定電流充放電操作模式。然而，單極式與雙極式電極接觸模式卻鮮少被研究討論。本研究目的為藉由電容去離子模組操作模式的最佳化，增進電容去離子模組的能源使用效率。實驗以連續式放大化電容去離子模組進行吸脫附實驗。電容去離子模組中活性碳電極有效面積為20 × 20 cm2，而處理水樣為濃度10 mM的氯化鈉溶液。研究將針對定電壓(施加電壓為1.2 V)、定電流(施加電流分別為0.15, 0.20, 0.25, 以及0.30 A)充電操作，以及單極、雙極式電極接觸實驗進行分析比對以及操作最佳化。
研究結果顯示，定電流操作模式較定電壓操作模式擁有更穩定的出流水質，且其能源使用效率為定電壓模式的1.54倍，而平均脫鹽速率為1.13倍，代表定電流較定電壓充電模式擁有更高的能源使用效率以及更高的平均脫鹽速率。另外，雙極式電極接觸模式較單極式電極接觸模式擁有更低的出流水濃度，且其能源使用效率比單極式高出10%，而平均脫鹽速率比單極式高出37%，代表雙極式電極接觸模式較單極式電極接觸模式擁有更高的能源使用效率以及更高的平均脫鹽速率。綜上所述，本研究結果指出，在考量整體脫鹽效果、能源使用效率，以及脫鹽速率之下，定電流充電模式優於定電壓充電模式，而雙極式電極接觸模式優於單極式電極接觸模式。

Development of low-energy demand water treatment technologies is a growing research priority in response to the global water and energy challenges. Capacitive deionization (CDI), a novel electrochemical technology for water desalination, offers several advantages such as low energy requirement, high water recovery, and environmental friendliness. Recently, investigation of different CDI operational charging modes (i.e., constant voltage and constant current operation) has drawn more attention due to that operational modes have crucial effects on energy efficiency and desalination performance of CDI device, especially for the scale-up one. However, for electrode connection mode, only a few researchers have investigated the effect of unipolar and bipolar connections on CDI performance, and little is known about the scale-up CDI stack operated in different electrode connections for desalination.
In this research, optimization of the energetic and desalination performances of a single-pass CDI device in constant voltage (voltage load = 1.2 V) charging mode, constant current (current load = 0.15, 0.20, 0.25, and 0.30 A) charging mode, unipolar connection, and bipolar connection were investigated. The effective surface area of each activated carbon electrode was 20 × 20 cm2, and the sample solution was 10 mM NaCl. Furthermore, evaluation on the key performances of CDI, including desalination capacity (DC), mean deionization rate (MDR), charge efficiency, specific energy input (Esalt), specific energy efficiency (SEE), and optimization product were conducted. SEE in bipolar connection was found to be 4.92 mg g−1 kJ−1, which was over 10% larger than that in unipolar connection. Besides, the MDR in bipolar connection was 0.085 mg g−1 min−1, which was 37% higher than that in unipolar connection. All of these results suggested that bipolar connection in CDI demonstrated preferred characteristics of higher desalination ability, and lower energy requirement. These parameters are also important for future development of scale-up CDI devices in water desalination.

誌謝 i
中文摘要 iii
Abstract iv
Contents vi
List of Figures viii
List of Tables xi
Chapter 1 Introduction 1
1.1 Background 1
1.2 Motivation and Objectives 1
Chapter 2 Theory and Literature Review 3
2.1 Development of Electrochemical Capacitors 3
2.2 Development of Capacitive Deionization 6
2.3 Operation Modes of CDI 9
2.3.1 Charging Mode: Constant Voltage and Constant Current 9
2.3.2 Connection Mode: Unipolar and Bipolar Connections 12
Chapter 3 Experimental 15
3.1 Materials and Instruments 15
3.2 Activated Carbon Electrodes 18
3.2.1 Fabrication of Electrodes 18
3.2.2 Analysis of Electrode Characteristics 18
3.3 CDI Device 23
3.4 CDI System 23
3.5 CDI Experiments in CV and CC Charging Modes 26
3.6 CDI Experiments in Unipolar and Bipolar Connections 27
3.7 Key Performance Indicators 30
Chapter 4 Results and Discussion 34
4.1 Electrode Characteristics 34
4.2 Comparison between CV and CC Charging Modes 37
4.3 Optimization of CV and CC Charging Modes 42
4.4 Comparison between Unipolar and Bipolar Connections 46
4.5 Optimization of Unipolar and Bipolar Connections 53
Chapter 5 Conclusions and Recommendations 57
References 58

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