Title Page
ABSTRACT
국문 초록
Contents
CHAPTER 1. Introduction 22
1.1. Backgrounds 23
1.2. Research objectives 25
CHAPTER 2. Research background 27
2.1. Comparison of FCDI with conventional and membrane-CDI 28
2.1.1. CDI and MCDI mechanisms 28
2.1.2. FCDI mechanism 30
2.2. Optimization of the FCDI process 31
2.2.1. Flow-electrode 32
2.2.2. Electrolyte 41
2.2.3. FCDI cell operation 48
2.3. Improving energy efficiency 51
2.3.1. Energy efficiency 52
2.3.2. Improvements for energy saving 53
2.3.3. Quantification of energy efficiency 56
2.3.4. Analysis of energy/economic feasibility 58
2.4. Potential FCDI applications 59
2.4.1. Energy-efficient desalination 60
2.4.2. Water softening 62
2.4.3. Toxic chemical control 64
2.4.4. Nutrient removal and recovery 64
2.5. Future direction for improving feasibility and applicability of FCDI 67
CHAPTER 3. Energetic comparison of flow-electrode capacitive deionization & membrane technology: Assessment on applicability in desalination fields 71
3.1. Introduction 72
3.2. Materials and methods 74
3.2.1. Experimental methods of the FCDI experiment 75
3.2.2. Theoretical modeling of the FCDI process 76
3.3. Results and discussion 80
3.3.1. FCDI performance modelling & operation optimization 80
3.3.2. Modelling comparison of the BWRO & FCDI processes 84
3.3.3. Modelling comparison of the SWRO & FCDI processes 91
3.3.4. Future direction for the comprehensive on-field application of FCDI process 97
CHAPTER 4. Enhanced capacitive deionization using a biochar-integrated novel flow-electrode 102
4.1. Introduction 103
4.2. Materials and methods 106
4.2.1. Feed solution 106
4.2.2. Flow-electrode solution 106
4.2.3. Experimental set-up 106
4.2.4. Analytical methods 108
4.2.5. Performance and energy consumption assessment 108
4.3. Results and discussion 110
4.3.1. Physico- and electrochemical characterization of AC and biochar 110
4.3.2. Optimization of FCDI operational condition (potential difference) 118
4.3.3. Assessment of FCDI performance using biochar-integrated flow-electrode 120
4.3.4. Application of biochar-integrated FCDI for remediation of model lead pollutant 123
4.3.5. Operation of biochar-integrated FCDI for treatment of lead-laden saline water 124
4.4. Conclusion 126
CHAPTER 5. Capacitive deionization incorporating a fluidic MOF-CNT electrode for the high selective extraction of lithium 129
5.1. Introduction 130
5.2. Materials and methods 132
5.2.1. Feed solution 133
5.2.2. Flow-electrode solution 133
5.2.3. Experimental set-up 134
5.2.4. Analytical methods 135
5.2.5. Calculation of operational performance 136
5.3. Results and discussion 137
5.3.1. Physio- and electrochemical characterization of AC and ZIF-8/CNT 137
5.3.2. Assessment of AC & ZIF-8/CNT incorporated FCDI system operation 141
5.3.3. Simultaneous capture and recovery of lithium via ZIF-8/CNT incorporated FCDI 146
5.4. Conclusion 149
CHAPTER 6. TiO₂ nanotube electrode for organic degradation coupled with flow-electrode capacitive deionization for brackish water desalination 151
6.1. Introduction 152
6.2. Results and discussion 156
6.2.1. Characterization of self-doped BM-TNA and BP-TNA electrodes 156
6.2.2. Effect of the novel catalyst and photoelectrochemical activity via UV-lights source 159
6.2.3. Removal of organic compounds and catalytic stability of the PEC system 162
6.2.4. Evaluation of the FCDI process operation via deionization and SEC 164
6.2.5. Evaluation on the performance of PEC-FCDI dual process 168
6.3. Materials and methods 171
6.3.1. Reagents 171
6.3.2. Feed solution 172
6.3.3. Flow-electrode solution 172
6.3.4. Fabrication of self-doped BM-TNA and BP-TNA electrodes 172
6.3.5. Experimental set-up 173
6.3.6. Analytical methods 175
6.3.7. FCDI performance and energy assessment 176
CHAPTER 7. Concluding remarks and further research 178
Reference 182
Supplementary 205
Table 2-1. Average salt adsorption rate of FCDI evaluated at different operating cell modes and with surface-modified flow-electrodes 40
Table 2-2. Evaluation of salt adsorption performance under various electrolytes and pH conditions 47
Table 3-1. Specific energy consumptions of real BWRO plant & simulated FCDI process by plant capacity. 89
Table 3-2. Specific energy consumptions of real SWRO plant & simulated FCDI process by plant capacity. 95
FIGURE 2-1. Schematic of (a) capacitive deionization (CDI); (b) membrane-capacitive deionization (MCDI); and (c) flow-electrode capacitive deionization (FCDI). 28
FIGURE 2-2. Schematic of various faradaic reactions in CDI process. 30
FIGURE 2-3. Historical development of various carbon-based electrode materials for FCDI. 33
FIGURE 2-4. Important operating parameters determining FCDI desalination performance. 44
FIGURE 2-5. Schematics summarizing the different flow-electrode operation modes. 51
FIGURE 2-6. Energy efficiency of flow-electrode capacitive deionization determined by charging and discharging, thus energy consumption and recovery. 52
FIGURE 2-7. Comparison of the thermodynamic energy efficiency (TEE) of electrochemical-based desalination approaches [102]: (a) CDI, MCDI, and FCDI with... 58
FIGURE 2-8. Potential applications of FCDI technology in (a) energy-efficient desalination; (b) selective water softening; (c) removal of toxic chemicals; and (d) recovery of nutrients. 60
FIGURE 2-9. Flow diagram of the conceptual (a) SWRO-FCDI; and (b) FCDI-MF hybrid processes for enhanced desalination efficiency. 62
FIGURE 2-10. Summary of FCDI system; current and future directions. 70
FIGURE 3-1. Schematic of the FCDI experimental setup. 76
FIGURE 3-2. Flow diagram of the FCDI process theoretical modelling based on numerical solution. 80
FIGURE 3-3. Comparison of the modelling and experimental values of the FCDI process (Removal efficiency vs Potential difference). 82
FIGURE 3-4. Comparison of the modelling and experimental values of the FCDI process in terms of removal efficiency with regards to operational parameters of (a) potential... 84
FIGURE 3-5. (a) FCDI permeate concentration depending on 'feed concentration' and 'potential difference' (dotted line representing the region pertaining to a permeate... 86
FIGURE 3-6. Comparison of the specific energy consumptions of the BWRO & FCDI processes by plant capacity. 88
FIGURE 3-7. (a) FCDI permeate concentration depending on 'feed concentration' and 'potential difference' (dotted line representing the region pertaining to a permeate... 92
FIGURE 3-8. Comparison of the specific energy consumptions of the SWRO & FCDI processes by plant capacity. 94
FIGURE 3-9. Specific energy consumption of the FCDI process by membrane area for the treatment of a target feed concentration of (a) 5,000 mg/L, (b) 35,000 mg/L, and (c) 50,000 mg/L. 98
FIGURE 3-10. Schematic diagram of a (a) submerged FCDI system with multi flow-electrode cartridge chamber configuration (adapted from [163]), (b) FCDI module adopted... 100
FIGURE 4-1. Schematic of the FCDI (a) experimental setup, and (b) unit cell. 107
FIGURE 4-2. Field-emission scanning electron microscope images of (a) low- and (b) high- resolution AC, (c) low- and (d) high-resolution biochar, and (e) low- and (f) high-resolution... 113
FIGURE 4-3. Fourier-transform infrared spectroscopy of AC, and biochar. 115
FIGURE 4-4. Zeta potential of AC, biochar, and AC + biochar composite flow-electrode solutions for different pH values. 116
FIGURE 4-5. Nyquist plot of AC, biochar, and AC + biochar composite (in different wt% compositions) flow-electrode solutions. 118
FIGURE 4-6. (a) Conductivity of permeate solution and (b) salt adsorption capacity of flow-electrode capacitive deionization system ([NaCl]₀=500 mg/L; [AC flow-electrode mass... 120
FIGURE 4-7. (a) Ion removal and (b) specific energy consumption of flow-electrode capacitive deionization system ([NaCl]₀=500 mg/L; [flow-electrode mass loading]=10... 123
FIGURE 4-8. Synthesis and characterization of AC and Biochar ([Pb²⁺]₀=100 mg/L; [flow-electrode mass loading]=10 wt%; [flow-electrode composition]="AC 45 g," "AC 40 g +... 124
FIGURE 4-9. Two-pass operation of FCDI system ([NaCl]₀=500 mg/L, [Pb²⁺]₀=100 mg/L, pHi=7.0; [flow-electrode mass loading]=10 wt%; [flow-electrode composition]...[이미지참조] 126
FIGURE 5-1. Schematic diagram of the FCDI experiment set-up: (a) one-stage deionization operation, and (b) two-stage deionization-recovery operation. 135
FIGURE 5-2. Field-emission scanning electron microscope (FE-SEM) images (a) low- and (b) high-resolution ZIF-8; (c) low- and (d) high-resolution ZIF-8/CNT; (e) AC; and (f) EDS... 138
FIGURE 5-3. (a) X-ray diffraction (XRD) pattern of ZIF-8/CNT composite, and (b) Brunauer-Emmett-Teller (BET) analysis of AC and ZIF-8/CNT. 140
FIGURE 5-4. Electrochemical impedance spectroscopy (EIS) analysis of AC and ZIF-8/CNT. 141
FIGURE 5-5. (a) Conductivity of the feed reservoir, (b) system current, (c) pH of the flow-electrode solutions, and (d) specific energy consumption (SEC) of the AC and ZIF-8/CNT... 144
FIGURE 5-6. Concentrations of lithium, nickel and manganese ions within the electrolytic solutions of the (a) AC flow-electrode and the (b) ZIF-8/CNT flow-electrode, and the (c)... 146
FIGURE 5-7. Concentrations of lithium, nickel and manganese ions (a) within the feed solution during the first-stage FCDI adsorption operation, (b) within the permeate solution... 148
FIGURE 6-1. Characterization of the BM- and BP-TNA electrodes via SEM, XPS, and XRD analyses. SEM images of (a), (b) BM-TNA and (c), (d) BP-TNA; (e) XPS signals and... 158
FIGURE 6-2. Nyquist plot, and degradation of benzoic acid using BM- and BP-TNA electrodes under UV. (a) Nyquist plot (BM-TNA / BP-TNA) and (b), (c) benzoic acid... 162
FIGURE 6-3. Organic degradation via BM-TNA electrode, and evaluation of electrode stability. (a) Organic compound removal efficiency of BM-TNA under the... 164
FIGURE 6-4. Deionization performance and relative energy consumption of the FCDI system. (a) Ion removal efficiency, and (b) specific energy consumption of the flow-... 167
FIGURE 6-5. Operation of the PEC-FCDI dual system. PEC-FCDI dual system (PEC: [bisphenol-A]₀=0.1 mM, pHi=7.0; operation time=60 min) (FCDI: [NaCl]₀=1,947 mg/L,...[이미지참조] 170
FIGURE 6-6. Process schematic of the PEC-FCDI operation. 174