Inhibited phase behavior of gas hydrates in graphene oxide: influences of surface and geometric constraints

Kim, Daeok,Kim, Dae Woo,Lim, Hyung-Kyu,Jeon, Jiwon,Kim, Hyungjun,Jung, Hee-Tae,Lee, Huen The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.41

<P>Porous materials have provided us unprecedented opportunities to develop emerging technologies such as molecular storage systems and separation mechanisms. Pores have also been used as supports to contain gas hydrates for the application in gas treatments. Necessarily, an exact understanding of the properties of gas hydrates in confining pores is important. Here, we investigated the formation of CO<SUB>2</SUB>, CH<SUB>4</SUB> and N<SUB>2</SUB> hydrates in non-interlamellar voids in graphene oxide (GO), and their thermodynamic behaviors. For that, low temperature XRD and <I>P</I>–<I>T</I> traces were conducted to analyze the water structure and confirm hydrate formation, respectively, in GO after its exposure to gaseous molecules. Confinement and strong interaction of water with the hydrophilic surface of graphene oxide reduce water activity, which leads to the inhibited phase behavior of gas hydrates.</P> <P>Graphic Abstract</P><P>Structural changes of water confined in graphene oxide to gas hydrates were investigated using low temperature XRD. It was revealed that the phase equilibrium points of gas hydrates strongly inhibited due to the surrounding nano-sized voids and the hydrophilic surface of graphene oxide. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp03263b'> </P>

Intercalation of Gas Molecules in Graphene Oxide Interlayer: The Role of Water

Kim, Daeok,Kim, Dae Woo,Lim, Hyung-Kyu,Jeon, Jiwon,Kim, Hyungjun,Jung, Hee-Tae,Lee, Huen American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.20

<P>Intercalation phenomena of gas molecules in the interlayer of graphene oxide have been investigated using CO<SUB>2</SUB>, CH<SUB>4</SUB>, H<SUB>2</SUB>, and N<SUB>2</SUB> gases. Intercalation of gas molecules is highly affected by the affinity between the hydrophilic surface of GO and target molecules. Among tested gases, CO<SUB>2</SUB> can only be intercalated. Furthermore, the swelling of interlayer changed the intercalation phenomena. Amounts of intercalated gases are significantly enhanced, and all the gases can be intercalated by retarded dynamics of intercalated water.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-20/jp5026762/production/images/medium/jp-2014-026762_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5026762'>ACS Electronic Supporting Info</A></P>

Phase Equilibria of CO₂ and CH₄ Hydrates in Intergranular Meso/Macro Pores of MIL-53 Metal Organic Framework

Kim, Daeok,Ahn, Yun-Ho,Lee, Huen American Chemical Society 2015 Journal of chemical and engineering data Vol.60 No.7

<P>The formation of gas hydrates in porous media is expected to bring out beneficial properties for gas storage and separation. Appropriate combined use of both gas hydrate and highly porous metal organic frameworks (MOFs) can be useful for achieving advances in the field of gas storage and separation. This makes understanding the behavior of gas hydrates in the confining pores of MOF crucial. The formation and phase equilibria of CO<SUB>2</SUB> and CH<SUB>4</SUB> hydrates in MOF were investigated using MIL-53 MOF through low-temperature synchrotron high-resolution powder diffraction (HRPD) and <I>P</I>–<I>T</I> traces. MIL-53 has both intrinsic micropores and intergranular meso/macropores. Gas hydrate forms in meso/macropores, and its thermodynamic behavior is relatively inhibited compared to its behavior in bulk phase due to reduced water activity. However, a strong CO<SUB>2</SUB> dissolution appeared instead of gas hydrates in the intrinsic micropores of MIL-53. This led to a notable phenomenon in which the cooling and heating lines in the <I>P</I>–<I>T</I> trace curves of CO<SUB>2</SUB> hydrate did not intersect near the dissociation point of CO<SUB>2</SUB> hydrate.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jceaax/2015/jceaax.2015.60.issue-7/acs.jced.5b00322/production/images/medium/je-2015-00322y_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/je5b00322'>ACS Electronic Supporting Info</A></P>

Continuous ZIF-8/reduced graphene oxide nanocoating for ultrafast oil/water separation

Kim, Dae Woo,Eum, Kiwon,Kim, Hanim,Kim, Daeok,Mello, Matheus Dorneles de,Park, Kangho,Tsapatsis, Michael Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.372 No.-

<P><B>Abstract</B></P> <P>Continuous ZIF-8/reduced graphene oxide (RGO) nanocoating is fabricated by growing ZIF-8 on RGO-coated polyurethane (PU) foam. Surface modification of PU foam can be easily achieved by immersing the PU foam in GO solution, followed by mild thermal treatment to turn the GO layer into RGO layer. Adhesion between polymer foam and ZIF-8 layer was enhanced by the inserted RGO layer because oxygen-containing groups of RGO could interact with Zn<SUP>2+</SUP> precursor of ZIF-8 localizing the layer growth preferentially on the surface of RGO. The synergetic hydrophobic/oleophilic properties of RGO and ZIF-8 enable selective oil absorption of PU foam with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. Most of all, the ZIF-8/RGO coated PU foam can filter organic solvent selectively <I>via</I> vacuum filtration, showing ultrafast hexane flux up to 800,000 Lm<SUP>−2</SUP> h<SUP>−1</SUP> and no water flux.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A method to fabricate continuous hydrophobic/oleophilic RGO/ZIF-8 nanocoating on polymeric foam. </LI> <LI> Selective oil absorption with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. </LI> <LI> Ultrafast hexane flux up to 800,000 Lm<SUP>−2</SUP> h<SUP>−1</SUP> and no water flux during vacuum filtration. </LI> <LI> Universal method to fabricate metal-organic frameworks on polymeric foam. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Gas Hydrate in Crystalline-Swelled Clay: The Effect of Pore Dimension on Hydrate Formation and Phase Equilibria

Kim, Daeok,Ahn, Yun-Ho,Kim, Se-Joon,Lee, Joo Yong,Lee, Jeahyoung,Seo, Young-ju,Lee, Huen American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.38

<P>Understanding of gas hydrates, for example, phase equilibria, in reservoir sediments is one of the important issues in the fields of energy production and CO<SUB>2</SUB> sequestration via CH<SUB>4</SUB> hydrate exploitation and CO<SUB>2</SUB> hydrate formation. The composition of water in clay can change their physical properties, which influences the state in which gas hydrates exist in clays. We investigated gas hydrates in crystalline-swelled Na-montmorillonite (CS-mon) having water content of <27 wt % and maintaining crystallinity of clay particles. Instead of a gas hydrate forming in the interlayer, gas is dissolved in the swelled interlayers of clay, acting as a favorable storage site for hydrophilic CO<SUB>2</SUB>. In addition, gas hydrates formed in CS-mon showed both inhibited and promoted phase behavior. This revealed that the clay surface can promote the formation of a hydrate structure, but confinement in nanosized space dominates the promotion effect and causes stronger inhibition than in the bulk phase. We believe that our results not only broaden the understanding of gas hydrates in confining systems and porous materials but also provide a precise explanation of the behavior of gas hydrates in clay sediment.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-38/acs.jpcc.5b03229/production/images/medium/jp-2015-03229f_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03229'>ACS Electronic Supporting Info</A></P>

Face Recognition Based on Facial Landmark Feature Descriptor in Unconstrained Environments

김대옥(Daeok Kim),홍종광(Jongkwang Hong),변혜란(Hyeran Byun) Korean Institute of Information Scientists and Eng 2014 정보과학회논문지 Vol.41 No.9

A contribution of brown carbon aerosol to the aerosol light absorption and its radiative forcing in East Asia

Minjoong J. Kim,Rokjin J. Park,Jaein I. Jeong,Daeok Youn,Sangwoo Kim 한국기상학회 2009 한국기상학회 학술대회 논문집 Vol.2009 No.10

On the multiday haze in the Asian continental outflow: the important role of synoptic conditions combined with regional and local sources

Seo, Jihoon,Kim, Jin Young,Youn, Daeok,Lee, Ji Yi,Kim, Hwajin,Lim, Yong Bin,Kim, Yumi,Jin, Hyoun Cher Copernicus GmbH 2017 Atmospheric Chemistry and Physics Vol.17 No.15

<P>Abstract. The air quality of the megacities in populated and industrialized regions like East Asia is affected by both local and regional emission sources. The combined effect of regional transport and local emissions on multiday haze was investigated through a synthetic analysis of PM2. 5 sampled at both an urban site in Seoul, South Korea and an upwind background site on Deokjeok Island over the Yellow Sea during a severe multiday haze episode in late February 2014. Inorganic components and carbonaceous species of daily PM2. 5 samples were measured, and gaseous pollutants, local meteorological factors, and synoptic meteorological conditions were also determined. A dominance of fine-mode particles (PM2. 5 ∕ PM10 ∼ 0.8), a large secondary inorganic fraction (76 %), high OC ∕ EC (> 7), and highly oxidized aerosols (oxygen-to-carbon ratio of ∼ 0.6 and organic-mass-to-carbon ratio of ∼ 1.9) under relatively warm, humid, and stagnant conditions characterize the multiday haze episode in Seoul; however, the early and late stages of the episode show different chemical compositions of PM2. 5. High concentrations of sulfate in both Seoul and the upwind background in the early stage suggest a significant regional influence on the onset of the multiday haze. At the same time, high concentrations of nitrate and organic compounds in Seoul, which are local and highly correlated with meteorological factors, suggest the contribution of local emissions and secondary formation under stagnant meteorological conditions to the haze. A slow eastward-moving high-pressure system from southern China to the East China Sea induces the regional transport of aerosols and potential gaseous precursors for secondary aerosols from the North China Plain in the early stage but provides stagnant conditions conducive to the accumulation and the local formation of aerosols in the late stage. A blocking ridge over Alaska that developed during the episode hinders the zonal propagation of synoptic-scale systems and extends the haze period to several days. This study provides chemical insights into haze development sequentially by regional transport and local sources, and shows that the synoptic condition plays an important role in the dynamical evolution of long-lasting haze in the Asian continental outflow region. </P>

Detection, Identification and Characterization of In vitro GSH Metabolites Formed by 1- and 2-Bromopropane

Lee EungSeok,Moon YoonSoo,Kim EunKyung,Basnet Arjun,Zhao LongXuan,Kim DaeOk,Kim NamHee,Chae Whigun,Jeong TaeCheon 大韓藥學會 2003 大韓藥學會 總會 및 學術大會 Vol.2003 No.2

블루투스를 이용한 위치기반 지하철 정보 서비스

정승호(Seungho Cheong),김대옥(Daeok Kim),박종광(Chongkwang Park),김광환(Kwanghwan Kim),이은철(Eunchul Lee),김교선(Kyosun Kim) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10

The subway passengers are usually alert to the current location of the train in order not to miss the destination or transfer stations. The Global Positioning System (GPS), although expensive, can give an alarm if properly programmed, but cannot receive the satellite signals, underground. Therefore, a novel approach to context-aware location-based subway information system is motivated. The passengers, who are equipped with mobile devices such as laptop, PDA, and mobile phone as clients of the Personal Area Network (PAN), request the Bluetooth connection to the server which is installed in each car of the train. While the server broadcasts the location-based information including the previous station, the current velocity of the train, the distance and time to the next station, the clients provide additional services based on the recognized context of the information, and what the passengers individually want. The services are spontaneous and autonomous rather than passive. The services include not only the information on the nearby stations, exit numbers, connection buses but also the location-based alarms which can be set specific to various personal requests, and sounded by the location of the train rather than time. Whereas the arrival time may not he accurate due to the delays of the train, the location can be accurately traced and broadcast by the server. Also, the clients do not need any expensive systems like GPS. Towards validating the proposed approach, we implemented a Bluetooth PAN including a PC server, two PDA clients and a laptop client. We modeled a train on the Incheon Subway Line #1 and a train on the Seoul-to-Incheon Line on the server, simulated the virtual trains together with the real clients. and verified that all the services were successfully provided.