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Development and investigation of ion selective materials for high performance capacitive deionization
고성능 축전식 담수화 공정을 위한 이온 선택성 물질 개발과 역할 규명

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dc.contributor.advisor윤제용-
dc.contributor.author윤홍식-
dc.date.accessioned2018-05-28T16:29:20Z-
dc.date.available2018-05-28T16:29:20Z-
dc.date.issued2018-02-
dc.identifier.other000000150938-
dc.identifier.urihttps://hdl.handle.net/10371/140743-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 공과대학 화학생물공학부, 2018. 2. 윤제용.-
dc.description.abstractCapacitive deionization (CDI) is an emerging desalination process that produces fresh water from saline. CDI has been getting attentions due to its energy efficiency compared to the traditional desalination processes such as thermal distillation and reverse osmosis (RO). However, there is an intrinsic limitation in traditional CDI system. It is co-ion expulsion issue. When the electrical double layer formed on the electrode, some of charges are wasted, leading to the deionization performance reduction. To overcome these disadvantages, ion selective materials such as ion exchange membrane and battery materials have been introduced in CDI system. Recently, various materials have been vigorously developed for CDI system. However, the suitable ion selective material has been still required which would be expected to be highly performed, cost effective, and easily processible. Therefore, this study develops new ion selective materials to enhanced CDI performance. In addition, the effect of the ion selective materials on the CDI performances was also investigated.
First, Ca-alginate was proposed as an alternative to cation exchange membrane (CEM) in CDI system for hardness control. Ca-alginate, a cost effective and eco-friendly polymer gel, is widely used in pharmaceutical, water treatment, and food-industries. Ca-alginate was successfully coated on the negative electrode using phase separation via sodium-calcium exchange. As a major result, the CDI with Ca-alginate coated electrode (CA-CDI) showed superior deionization performance (approximately 44%) than conventional CDI system. Moreover, MCDI system with Ca-alginate coated electrode had comparable deionization capacity and charge efficiency to conventional MCDI system with commercial cation and anion exchange membranes.
Secondly, Ag coating on to the carbon electrode was proposed to enhance the deionization performances. The Ag coated carbon composite electrode was made by coating a small amount of Ag onto a carbon capacitive electrode, exhibiting the characteristics of a battery and a capacitor together. As major results, the CDI deionization capacity (88% more), rate (39% more), and charge efficiency (76%  92%) were dramatically enhanced due to the Ag coating. The significant improvements in deionization performances are explained by the enhanced specific capacity combining the capacitance in the carbon electrode with the Ag mediated charge transfer reaction. In addition, the hybrid CDI with Ag coated carbon composite electrode (73.3 kJ mole-1) is superior to membrane assisted CDI (136.7 kJ mole-1) in terms of energy consumption for deionization due to its low voltage feasible operation.
Lastly, it was investigated how the characteristics of ion exchange membrane (IEM) affect the membrane CDI (MCDI) performance. As MCDI performances, deionization capacity, maximum average deionization rate (MADR), and charge efficiency were analyzed. As major results, only MADR was significantly affected by change of IEM characteristics. In addition, MADR showed good positive relationship with transport number divided by total electrical resistance.
In conclusion, the research works of this dissertation indicate that the fascinated ion selective materials such as Ca-alginate and Ag coating significantly developed a superior deionization performance and showed great potential for further development in the CDI (MCDI) systems. In addition, the study revealing the relationship between t+/RCEM and MADR would be expected to provide a good insight to develop of highly fast rate-capable MCDI.
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dc.description.tableofcontents1. Introduction 1
1.1. Backgrounds 1
1.2. Objectives 3
2. Literature review 5
2.1. Capacitive deionization 5
2.2. Membrane capacitive deionization (MCDI) 8
2.2.1. Ion exchange membrane 8
2.2.2. The role of Ion exchange membrane in MCDI 11
2.2.3. New membrane materials for MCDI 13
2.2.4. New coating materials for MCDI 17
2.2.5. Stability of Cation/Anion exchange membrane 26
2.3. Selective ion removal in capacitive deionization (CDI) 30
2.3.1. Selectivity in CDI carbon based electrode 30
2.3.2. Selectivity in membrane capacitive deionization (MCDI) 35
2.3.3. Selectivity in capacitive deionization with faradaic reaction and aqueous battery desalination system 38
2.3.4. Application of CDI selectivity 42
3. Capacitive deionization with Ca-alginate coated-carbon electrode for hardness control 45
3.1. Introduction 45
3.2. Materials & methods 47
3.2.1. Electrode preparation 47
3.2.2. Calcium alginate coating on the carbon electrode 48
3.2.3. Characterization of the Ca-alginate layer 49
3.2.4. Electrochemical characterization of the Ca-alginate coated-electrode 50
3.2.5. Deionization performance test 54
3.2.6. Ion selective removal test 57
3.3. Results and Discussion 59
3.3.1. Characteristics of the Ca-alginate coated-electrode 59
3.3.2. Deionization performance 64
3.3.3. Deionization performance with a mixed solution 72
3.4. Summary 77
4. Hybrid capacitive deionization with Ag coated carbon composite electrode 78
4.1. Introduction 78
4.2. Materials & methods 82
4.2.1. Preparation of the capacitive carbon electrode 82
4.2.2. Silver coated carbon composite electrode 82
4.2.3. Characterization of the Ag coated CDI carbon electrode 84
4.2.4. Deionization performance test 85
4.2.5. Performance test of Ag coated HCDI with real river water 89
4.3. Results and Discussion 90
4.4. Summary 106
5. Relationship between the characteristics of cation exchange membrane and their desalination performances in membrane capacitive deionization 107
5.1. Introduction 107
5.2. Materials & Methods 109
5.2.1. Electrode fabrication 109
5.2.2. Cation exchange membrane 110
5.2.3. Characterization of cation exchange membrane 111
5.2.4. Deionization performance test 114
5.3. Results and Discussion 116
5.4. Summary 130
6. Conclusion 131
Reference 133
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dc.formatapplication/pdf-
dc.format.extent4559799 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectWater treatment-
dc.subjectDesalination-
dc.subjectCapacitive deionization-
dc.subjectSilver-
dc.subjectCa-alginate-
dc.subject.ddc660.6-
dc.titleDevelopment and investigation of ion selective materials for high performance capacitive deionization-
dc.title.alternative고성능 축전식 담수화 공정을 위한 이온 선택성 물질 개발과 역할 규명-
dc.typeThesis-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 화학생물공학부-
dc.date.awarded2018-02-
Appears in Collections:
College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Theses (Ph.D. / Sc.D._화학생물공학부)
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