‘Upper bound’ is very well known notion in membrane field, which explains the trade-off relationship between permeability and selectivity in gas pairs. Many researches have worked on overcoming the current limitation in order to develop cost-effective and energy-efficient membrane system. Thus, understanding the intrinsic material properties (permeation, diffusivity and solubility) are prerequisite to set the strategy how to get over the upper bound. In this study, we introduced Quartz crystal microbalance to measure diffusion coefficient and compare the results to apparent diffusivity value obtained from the high-vauum time lag method. We consider the quartz type, temperature and pressure effect on diffusion coefficient and also characterize defect density of deposited film.

Recently, a few-layered graphene oxide (GO), which high CO2/N2 selective characters in the humidified feed, has been extensively investigated as a membrane material for gas and liquid separation. Although GO membrane is considered as one of promising membranes, it has a limitation to apply for practical application because of low CO2 permeance and low stability under dry condition. As such, in this study, we fabricated CO2-philic polymers and GO composite membranes by using GO as a filler for high CO2/N2 selectivity. We used two kinds of PEO-containing polymers to increase CO2 permeability by controlling the ratio of free volume in polymer networks. High CO2 permeability (~850barrer) and high CO2/N2 selectivity (~55) were achieved in CO2-philic composite membranes.

Graphene-based derivatives such as graphene oxide(GO) have great potential as membrane material due to their controllable d-spacing, extremely large surface area and tunability of multifunctional groups. GO, highly oxidized graphene, has especially good affinity to CO2 arose from its oxide functional groups(e.g. carboxylic acid, hydroxyl groups) on 2-D nanosheet plane. Here, we synthesized GO/polymer composite materials and fabricated large-area thin film composite(TFC) membrane for CO2 separation using polymeric porous support. Further, we have produced flat-sheet membrane modules with the TFC membranes and tested the performance of the module under CO2/N2 mixed gas and flue gas conditions. The membrane module exhibited high CO2 separation performance as 74% of purity and 22% of recovery under flue gas condition including CO2, O2 and N2.

Thin-film nanocomposite (TFN) reverse osmosis (RO) membranes have drawn keen attention to overcome the limitations in polymeric desalination membranes. However, preparation of TFN-RO membranes using conventional protocol involves problems such as a waste of expensive nanomaterials and inaccurate control of loading amount. In this work, we suggest a new protocol of TFN-RO membranes through pre-adsorption of carbon nanotubes (CNTs) on the support layer using spray coating. SEM images of spray coated supports showed well-dispersed adsorption of CNTs compared with those using conventional method. RO performances of TFN membranes using spray coating were comparable to conventionally prepared membranes. Thus, this new protocol is useful to prepare TFN membranes in terms of cost-efficiency.

Owing to high energy efficiency and superior efficacy, membrane-based desalination processes have gained widespread implementation in a wide variety of water treatment applications. Tremendous research efforts on new membrane materials have been made to improve the separation performance of the state-of-the-art thin-film composite (TFC) membranes, particularly polyamide TFC membranes, hoping to overcome the permeability-selectivity trade-off relations. Currently, many nanomaterials such as zeolites, metal-organic frameworks (MOFs), graphene oxide (GO), and carbon nanotubes (CNTs) have been explored to enhance the separation performance of existing polymeric membranes, but it has been argued that the positive transformation of nanomaterials-embedded TFC membranes hold promising potential to realize the sustainable development of current desalination membranes. Here we have tried to discuss some misconceptions and challenging items delaying industrial-scale implementation of nanomaterialsembedded desalination membranes.

그래핀 기반 소재는 높은 가공성과 초박성으로 인하여 분리막 소재로서 각광받고 있다. 본 연구에서는, 스핀 코팅 법을 이용하여 제조된 산화그래핀 분리막의 기체 투과 거동을 평가하였다. 산화그래핀 분리막의 구조는 산화그래핀의 크기와 산화그래핀 용액의 pH 조절을 통하여 조절될 수 있다. 산화그래핀의 크기가 작을수록 굴곡률이 작아짐에 따라 분리막의 기 체 투과도 및 선택도가 증가하는 경향을 보인다. 또한 산화그래핀에서의 기체 투과 거동은 적층된 산화그래핀 사이의 채널 크기에 따라 영향을 받는다. 특히 산화그래핀 분리막의 좁은 기공과 이산화탄소 선택적인 산화그래핀 자체의 특성으로 인하 여 산화그래핀 분리막은 이산화탄소에 대한 높은 투과도 및 선택성을 가지며, 이는 이산화탄소 포집에 적합한 특성을 가진다. 이러한 산화그래핀 분리막의 특이한 기체 투과 거동은 흡착-촉진 확산 거동(표면 확산 기작)으로 설명될 수 있다. 본 연구를 통하여 이산화탄소 선택성 분리막 소재 설계와 슬릿 형태의 기공과 적층 구조를 가진 분리막을 통한 기체 투과 거동 연구가 활발히 이루어질 것으로 기대한다.

식품 포장, 전자 기기 등에 활용되고 있는 고분자 기반 기체 차단성 필름은 경량성, 낮은 제조 원가, 높은 가공성 으로 인하여 많은 주목을 받고 있다. 특히 전자기기에 활용되기 위하여, 기체 차단 필름은 매우 높은 수준의 기체 차단성을 요구받고 있다. 하지만 현재 수준의 고분자 기반 기체 차단 필름은 다른 소재와 비교하여 상대적으로 높은 수준의 기체 투과 유량을 보이고 있다. 따라서 기존의 고분자 필름이 가지고 있는 장점을 유지하면서 더 높은 수준의 기체 차단성을 부여하기 위한 요구가 증대되고 있다. 최근 그래핀 소재는 기체 차단을 위한 2차원 소재로서 각광받고 있다. 그러나 그래핀 소재의 낮 은 가공성과 어려운 대면적화 문제 때문에 산화그래핀이 그 대안으로서 떠오르고 있다. 산화그래핀은 높은 종횡비를 가지는 2차원 층상구조의 그래핀에 산소관능기를 함유한 형태로서, 수용성 혹은 극성 용매에 잘 분산되는 성질을 가지며, 따라서 대 량 생산에 용이한 특성을 가지고 있다. 본 연구에서는, 산화그래핀이 함유된 폴리이미드 나노복합막을 제조하였다. 폴리이미 드는 현재 널리 이용되고 있는 기체 차단성 고분자 중의 하나로서 높은 기계적 강도, 열적 안정성 및 내화학성을 가지고 있 다. 본 연구를 통하여 산화그래핀이 함유된 폴리이미드 나노복합막이 기체 차단성을 가지고 있음을 확인하였다. 더 나아가, Triton X-100이나 sodium deoxycholate (SDC) 등의 계면활성제를 나노복합막에 도입함으로써 산화그래핀의 고분자 매트릭스 내에서의 분산성을 향상시켜 기체 차단성을 높이고자 하였다. 그 결과로서, Triton X-100이 도입된 나노복합막이 예상치와 유 사한, 향상된 기체 차단성을 보임을 확인하였다. 본 연구를 기반으로 고분자 기반 나노복합막의 기체 차단성 분야로의 활용성 이 증대될 것으로 기대한다.

Graphene oxide (GO) has received a lot of attention in membrane science for its CO2-philic nature, which can facilitate CO2 separation performance. In addition, GO has attractive properties for gas separation membrane material due to thin-film membrane formation and tunable transport channel. GO membrane can be generally prepared by coating GO nanosheets on microporous polymer supports for mechanical stability. However, the substrates for in thin GO layer should be carefully chosen for good adhesion between GO layer and support surface with maintaining good separation performance. In this study, we tried to modify the surface properties of high permeable support membranes by using gutter layer as an intermediate layer, and measured the gas transport properties of these GO thin-film composite membranes.

Recently, graphene oxide (GO) has been extensively investigated for gas and liquid separation because thin-film GO membranes show quite interesting separation performance. However, even GO membranes exhibit relatively low gas permeability due to high tortuosity caused by high aspect ratio of GO. Normally, the size of GO is in the range from a few hundred nanometers to a few micrometers, so inherent gas permeability would be very varied. For practical applications of GO membranes, the gas permeability should be improved. As such, in this study, we have modified the pristine GO sheets to reduce the gas permeation pathway, with maintaining GO’s excellent gas separation properties. This study will provide a further insight on how such two-dimensional nanosheets can be used for membrane applications, competing with existing membrane materials.

Graphene is well-known as a perfect barrier because of its dense and delocalized cloud consisting of p-orbitals. However, graphene membrane synthesized by chemical vapor deposition (CVD) intrinsically contains structural defects (e.q., grain boundaries and point defects), which allow any small molecules to penetrate through the defective graphene membrane. Here we prepared polycrystalline graphene membranes including such defects, and investigated the gas transport behavior through the graphene membrane. Also, we compared the gas permeation behavior (or barrier properties) of large-area, single crystalline graphene membrane without any structural defects.

Graphene oxide (GO) is an intriguing two-dimensional nanosheet, a highly oxidized graphene sheet. Due to its various oxygen-containing polar functional groups, graphene oxide shows high CO2 sorption properties, and also thin-film GO membranes exhibit good CO2 separation properties, particularly in the presence of water molecules. Recently, GO nanosheets have been incorporated into polymer membranes, in the form of mixed-matrix membranes, to expect the synergistic effect of GO and polymer matrix. Here, we prepared novel GO/polymer membranes via crosslinking reactions between polar groups on basal plane of GO and bi-functional crosslinking agents, and then conducted the gas permeation measurements to see the possible enhancement for permeability/selectivity performance.

Graphene oxide (GO) can be used as a membrane material itself or a nanofiller to enhance gas separation performance of polymer membranes. Since GO has high CO2 affinity due to some polar groups, particularly GO membranes or GO/polymer membranes have been extensively studied for CO2 separation. Although ultrathin GO membranes show outstanding CO2 separation properties, the gas permeance through GO membranes is still low owing to high tortuosity caused by high aspect ratio of GO sheets. In this study, mixed-matrix membranes consisting of modified GO (as a dispersed phase) and high permeable polymer were prepared by combining each advantage of GO and high permeable polymer for improving gas separation performance. Both single-gas and mixed-gas permeation experiments were conducted with or without humidified feeds for post-combustion CO2 capture.

Carbon nanomaterials such as graphene and its derivatives can be used for membrane applications due to its scalable area and one-atom-thickness, if pores or channels can be well-engineered. Particularly, graphene oxide (GO), a highly oxidized graphene sheet, shows promising membrane building block for gas separation as well as liquid separation. Due to its various polar groups, GO-based membranes also show good candidate for CO2 separation. In this regard, we tried to prepare large-scale GO-based, thin-film composite membrane for post-combustion CO2 capture, and also fabricated membrane modules (e.g., spiral wound membrane or plate-and-frame modules) to apply for real flue gas separation. In this study, the separation performance of two kinds of membrane modules will be compared in terms of gas permeance, selectivity, and pressure drop.

Synthetic membranes, based on polymers or inorganic membranes, are now used in a wide variety of gas separations. For gas separation membranes, during the 1980’s, permeability data on six common gases were complied, and the tradeoff relationship was analyzed. The upper bound relationship was established empirically. Recognizing the exquisite permeability and selectivity of biological membranes and the deleterious nature of broad pore size distributions and flexibility of polymer chains on permeability/selectivity combinations, a number of approaches have been pursued to develop membranes with better transport and separation properties. There has been an evolution in design of materials for both gas and liquid separation membranes, brought about by advances in structural control of materials and by better understanding of natural membranes.

최근 폴리아마이드 선택층에 나노물질을 혼합하여 해수담수화 성능을 높이고자 하는 연구가 활발히 이루어지고 있다. 본 총설은 역삼투 분리막 해수담수화 공정에서의 에너지 효율 향상을 위한 우수한 성능을 가진 폴리아마이드 기반 나 노복합막을 소개하고자 한다. 그래핀 옥사이드 및 탄소나노튜브와 같은 탄소나노물질 및 제올라이트, 실리카 나노입자 등의 다양한 나노물질들이 기존 폴리아마이드의 투과분리성능을 높이기 위해 적용되고 있다. 본 총설에서는 최근 연구 중인 각 나 노소재별 성능향상 특장점을 소개하고, 더 높은 성능을 갖는 나노복합막 제조를 위한 연구방향을 제시하고자 한다.

Thin-film composite membranes (TFCs) have dominated desalination markets for recent decades, but a higher water permeance is still necessary to reduce the energy consumption. Although most researches have focused on the ultrathin active layer of TFCs, the supports should also be considered to further enhance the membrane performances. In this study, TFCs were fabricated on PSf supports containing carbon nanotubes (CNT) by interfacial polymerization. CNT/PSf supports show rougher and more porous surface morphologies than those of bare PSf supports. Because of such surface characteristics, CNT/PSf supports were favorable to increase the roughness and surface area of TFCs. Consequently, TFCs prepared on CNT/PSf nanocomposite supports showed a 41% enhanced water permeance without losing its salt rejection compared to the bare TFCs.

Membrane application for CO2 capture is competing with other methods such as amine absorption or absorbent, by reasons of low energy and cost effect. Though membrane separation is promising technology, there exists critical challenge: ‘the upper bound.’ Most of researches have focused on improving gas transport properties of selective layer, but we recognized the importance of membrane support layer shich highly affects affinity with coating layer. Here we adjusted several fabrication conditions for highly porous PAN membrane by NIPS method; concentration, temperature, and additive. In this study, experimental results regarding porosity and pore size, are compared to theoretical dusty-gas model. Moreover, we prepared composite membrane and compared fabricated membrane with commercial one in terms of gas permeance and selectivity.

Usually olefin/paraffin separations (e.g., ethane/ethylene and propane/ propylene) by distillation process are energy-intensive because such molecules have very similar molecular size and boiling point. Membrane process has been considered as an alternative method to achieve energy- efficient olefin/paraffin separation. However, based on solution-diffusion mechanism, it is hard to design good membrane materials to separate them efficiently. Here we report fundamental separation properties of olefin/paraffin through graphene oxide (GO) membranes having slit-like channels. Analogue to carbon molecular sieve membranes, GO membranes showed ability to separate these molecules. To improve the separation properties, GO membranes have been modified by various methods.

Graphene oxide (GO), a highly oxidized graphene sheet, is a distinguished 2-D nanosheet. GO membranes exhibit good CO2 separation properties due to its various polar functional groups with oxygen resulting in high CO2 sorption properties. Recently, GO nanosheets have been incorporated into polymer membranes expecting the synergistic effect. There is, however, little research on GO as a crosslinker even though it has high potential due to available functional groups for further reaction. Here, we prepared GO/polymer membranes by crosslinking reactions between polar groups of GO and bi-functional polymer matrix at different temperatures. Optimum crosslinking condition was found by analyzing gas transport, chemical properties of samples. Degree of crosslinking in GO/polymer nanocomposites affected gas transport behavior.