Preparation of Functional Anion Exchange Membranes for Diffusion Dialysis and Electrodialysis

摘要

迄今为止，膜技术具有高效，低能耗，低成本，在工业分离过程中是一种重要的方法。膜技术中，扩散渗析和电渗析分离技术是最具吸引力的，许多研究人员为此做了很多研究。扩散渗析依据两边化学势的不同，而电渗析是通过电位差从水溶液或不带电荷溶液中分离出带电离子。在目前的工作中，合成出一系列的离子交换膜，并且应用于电渗析和扩散渗析。
　　首先，合成出具有咪唑官能基团的阴离子交换膜。先制备阴离子交换二氧化硅前驱体(AESP)，用1-甲基咪唑对烷基氯丙基三乙氧基硅烷(CPTS)烷基化的方法，后通过溶胶-凝胶法，将AESP、PVA和TEOS作交联剂制备出阴离子交换膜。制备的阴离子交换膜离子交换容量(IECs)在1.34-1.86mmol/g之间，含水率(WU)在44.11-118.86％之间。此外，该膜具有较好的热稳定性，优异的机械性能。扩散渗析实验表明，酸扩散系数(UH)范围是1.87-4.83×10-2m/h，分离因子(S)在12.72～52.5。
　　其次，具有吡啶功能基团的阴离子交换膜是通过吡啶盐、PVA和TEOS经过醚化反应和溶胶-凝胶过程制备出的。所得的膜表现出优异的热稳定性和机械性能。用于扩散渗析时，膜的酸扩散系数在1.74-2.48(10-2m/h)之间，分离因子在30.49-57.51之间。
　　另外，共价键交联吡啶的阴离子交换膜（AEMS）也被制备出。先通过4-(溴甲基)苯甲酸对吡啶烷基化而制备出前驱体吡啶盐，然后在TEOS存在的条件下，用已制备的前驱体吡啶盐和PVA进行酯化反应制备出相应的阴离子交换膜(AEMS)。膜性能是:分解温度(Td)在322-335℃之间，拉伸强度(TS)在43.74-47.23MPa之间，断裂伸长率(Eb)在262.59-474.44％之间。膜的酸扩散系数在1.28-1.88×10-2m/h之间，其中含40％PVA的阴离子交换膜具有最高的分离因子为71.35.
　　再次，另外一种阴离子交换膜(AEMS)通过双季铵化和合成的阴离子交换前驱体与PVA通过溶胶-凝胶法制备而成。阴离子交换前驱体是通过1，6-二溴己烷和三乙烯二胺(DABCO)烷基化反应在与环氧丙基三乙氧基硅烷开环反应制备出。制备的阴离子交换膜水的含水率(WU)在82.6-148.5％之间，离子交换容量(IEC)为0.61-0.86mmol/g。这些膜的拉伸强度(TS)为15.4-22.7MPa，断裂伸长率(Eb)在441.2-541.0％之间。在应用于扩散渗析时，酸扩散系数为30.0-44.9m/h×10-3，分离因子为20.9-32.3，扩散渗析结果都优于商业膜DF-120(UH=9×m/h×10-3，S=18.5)。
　　最后，基于溴化聚苯醚(BPPO)基础上，制备具有阳离子功能基团的阴离子交换膜并应用于电渗析。首先，将3，5-吡啶二羧酸甲基化，得到二羧酸吡啶作为阴离子交换膜(AEMs)制备材料之一。制备的阴离子交换膜的离子交换容量(IECs)为1.14-1.82mmol/g，含水率(WU)为18.41-43.67％。计算的每一个荷电基团所带的水分子数目在8.98-13.32范围内，膜的线性伸长率(LER)在7.61-16.19％之间，膜的厚度在68-102nm之间，膜面电阻在在4.33-2.01Ω.cm2之间，膜的迁移数在0.92-0.96之间。在电渗析法脱盐中，其结果与商业膜Neosepta AMX相比，基于溴化聚苯醚(BPPO)基础上制备的阴离子交换膜在脱盐过程中有着更佳的性能。

目录

声明

摘要

Abstract

Dedication

Acknowledgements

Table of contents

Abbreviations and Acronyms

List of figures

List of tables

List of schemes

Chapter 1 Introduction to ion exchange membranes

1．1．Etymology of membrane

1．2．Concepts and principles of ion exchange membranes

1．2．1．Anion exchange membranes (AEMs)

1．2．2．Cation exchange membranes (CEMs)

1．2．3．Homogeneous membranes

1．2．4．Heterogeneous membranes

1．2．5．Porous and non-porous membranes

1．2．6．Liquid membranes

1．2．7．Ceramic membranes

1．2．9．Interpenetrating polymer network membranes

1．3．Membrane technology based separation processes

1．3．1．Diffusion dialysis

1．3．2．Electrodialysis

1．4．Statement significance

1．5．Objectives and scope of research

Chapter 2 Experimental section

2．1．Materials and reagents

2．2．Methods of membranes preparation

2．3．Characterizations

2．3．1．Polymer characterization

2．3．2．Water uptake (WU)

2．3．3．Linear expansion ratio (LER)

2．3．4．Ion Exchange Capacity (IEC)

2．3．5．Thermal and mechanical analyses

2．3．6．Morphological analysis

2．3．7．Membrane area resistance

2．3．8．Transport number

2．3．9．Diffusion dialysis

2．3．10．Electrodialysis experiment

Chapter 3 Imidazolium functionalized anion exchange membrane blended with PVA for acid recovery via diffusion dialysis process

3．1．Introduction

3．2．Preparation of Anion Exchange Silica Precursor (AESP)

3．3．Membrane preparation

3．4．Results and Discussion

3．4．1．Membrane preparation and characterization of polymers

3．4．2．Ion exchange capacity and water uptake

3．4．3．Thermal and mechanical stabilities

3．4．4．Membrane morphologies

3．4．5．Diffusion dialysis

3．5．Conclusion

Chapter 4 Functionalized anion exchange membranes based on pyridine derivatives for diffusion dialysis

4．1．1．Introduction

4．1．2．Preparation of Anion Exchange Pyridinium Salt

4．1．3．Membrane preparation

4．1．4．Results and discussion

4．1．5．Conclusion

4．2．Covalently cross-linked pyridinium based AEMs with aromatic pendant groups for acid recovery via diffusion dialysis

4．2．1．Introduction

4．2．2．Synthesis of anion exchange precursor

4．2．3．Membrane preparation

4．2．4．Results and discussion

4．2．5．Conclusion

Chapter 5 Novel synthetic route to prepare doubly quaternized anion exchange membranes for diffusion dialysis application

5．1．Introduction

5．2．Synthesis of anion exchange precursor

5．3．Membrane preparation

5．4．Results and discussion

5．4．1．Synthesis of anion exchange precursor

5．4．2．Membrane preparation and characterization

5．4．3．Water uptakes (WU)，ion-exchange capacities ( IECs) and dimensional changes

5．4．4．Mechanical strengths of membranes

5．4．5．Thermal stabilities of membranes

5．4．6．Morphologies of membranes

5．4．7．Diffusion dialysis

5．5．Conclusion

Chapter 6 Anion exchange membranes with cationic head groups for electrodialysis application

6．1．Introduction

6．2．Synthesis of 3，5-pyridine dicarboxylate

6．3．Membrane preparation

6．4．Results and discussion

6．4．1．1H-NMR and IR studies

6．4．2．Water uptakes (WU)，ion-exchange capacities (IECs) and dimensional changes

6．4．3．Thermal and mechanical stabilities

6．4．4．Membrane atea resistance and transport number

6．4．5．Membrane morphologies

6．4．6．Electrodialysis performance

6．5．Conclusion

Chapter 7 General Conclusions and recommendations

7．1．General conchlsions

7．2．Recommendations

References