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Thermo-sensitive Electrospun Fibrous Magnetic Composite Sheets
Jungsu Choi,Jinu Kim,Heejae Yang,Frank K. Ko,Ki Hyeon Kim 한국자기학회 2015 Journal of Magnetics Vol.20 No.3
The PVDF fibrous composite filled with iron oxide nanoparticles were prepared by using the electrospinning technique. The electrospun composite have the thickness in the range of 60-80 μm with the average fibrous diameters of 500-900 nm. The magnetizations of PVDF fibrous composite filled with iron oxide nanoparticles showed 4.5 emu/g, 3.1 emu/g and 1.6 emu/g at 1.5 T of external magnetic field for 20 wt.%, 10 wt.% and 5 wt.% iron oxide nanoparticles, respectively. The heat elevation of the magnetic composite were measured under various AC magnetic fields, frequency and the ambient temperatures. The temperature reached up to 46.3℃ from 36oC at 128 Oe and 355 kHz for 20 wt.% iron oxide nanoparticles filled in PVDF fibrous composite sheet. The specific absorption rate of theses sheets increased from 0.041 W/g to 0.236 W/g with the increment of AC magnetic field from 90 Oe to 167 Oe at 190 kHz, respectively.
Three-dimensional (3D) palladium-zinc oxide nanowire nanofiber as photo-catalyst for water treatment
Choi, Jungsu,Chan, Sophia,Joo, Hyunjong,Yang, Heejae,Ko, Frank K. Elsevier 2016 Water research Vol.101 No.-
<P><B>Abstract</B></P> <P>Zinc Oxide Nano Wires (ZNWs) has been considered as a promising material for purification and disinfection of water and remediation of hazardous waste owing to its high activity and lower cost. In this study, three-dimensional (3D) structured palladium (Pd)/ZNWs were synthesized on the fabricated electrospun nanofibers and explored for enhancement of organic matter (OM) removal efficiency in water by suppressing electron–hole recombination during photocatalytic activity and increased surface area. The densely populated ZNWs were fabricated on the electrospun nanofiber by electroless plating (EP) and hydrothermal synthesis. In order to improve photocatalytic efficiency, a thin layer of Pd was coated prior to ZNWs growth to induce suppression of electron hole recombination produced during catalyst activity. The creation of a highly porous network of nanofibers decorated with ZNWs resulted in an increase of specific removal rate (SRR) of OM from 0.0249 to 0.0377 mg COD<SUB>Cr</SUB> removed/mg ZNWs-hr when ZNW were grown on a Pd layer. It is believed that the demonstration of OM removal in the water through Pd/ZNWs membrane and enhanced photocatalytic activity under UV irradiation from layered structure can broaden potential applicability of Pd/ZNWs membranes for various photo catalytic water treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3D structured ZNWs were uniformly grown on the palladium coated nanofibers. </LI> <LI> Enhancement of OM removal through suppressing electron hole recombination. </LI> <LI> Removal of OM was found to be 96.6% from the Pd/ZNWs nanofiber. </LI> <LI> Pd/ZNWs membrane provide a powerful photocatalyst process for water treatment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
WalkON Suit: A Medalist in the Powered Exoskeleton Race of Cybathlon 2016
Choi, Jungsu,Na, Byeonghun,Jung, Pyeong-Gook,Rha, Dong-wook,Kong, Kyoungchul IEEE 2017 IEEE robotics & automation magazine Vol.24 No.4
<P>The powered exoskeleton race in Cybathlon 2016 consisted of six challenging tasks that required a pilot with complete paraplegia to walk on a level floor, uphill, downhill, and on stairs; stand up and sit down; step on stones; and even pass through a tilted path. All of these tasks addressed exactly the requirements for a powered exoskeleton designed to assist with activities of daily living (ADL) for paraplegics. Every team brought unique technologies to achieve this goal.</P>
Palladium-Zeolite nanofiber as an effective recyclable catalyst membrane for water treatment
Choi, Jungsu,Chan, Sophia,Yip, Garriott,Joo, Hyunjong,Yang, Heejae,Ko, Frank K. Elsevier 2016 Water research Vol.101 No.-
<P><B>Abstract</B></P> <P>Zeolite is an exciting natural material due to its unique capability of ammonium nitrogen (NH<SUB>3</SUB> N) adsorption in water. In this study, multifunctional hybrid composites of zeolite/palladium (Ze/Pd) on polymer nanofiber membranes were fabricated and explored for sustainable contaminant removal. SEM and XRD demonstrated that zeolite and palladium nanoparticles were uniformly distributed and deposited on the nanofibers. NH<SUB>3</SUB> N recovery rate was increased from 23 to 92% when palladium coated zeolite was embedded on the nanofiber. Multifunctional nanofibers of Ze/Pd membranes were able to adsorb NH<SUB>3</SUB> N on the zeolites placed on the surface of fibers and palladium catalysts were capable of selective oxidation of NH<SUB>3</SUB> N to N<SUB>2</SUB> gas. The cycling of NH<SUB>3</SUB> N adsorption-oxidation, high flux, hydrophilicity, and flexibility of the membrane makes it a strong candidate for water treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Zeolite and palladium nanoparticles were uniformly deposited on the nanofibers. </LI> <LI> Palladium catalysts were capable of selective oxidation of NH<SUB>3</SUB> N to N<SUB>2</SUB> gas. </LI> <LI> Multifunctional nanofibrous membranes were able to absorb and remove NH<SUB>3</SUB> N. </LI> <LI> Ze/Pd nanofiber membrane can be recycled and reused for NH<SUB>3</SUB> N removal. </LI> <LI> Recovery rate of Ze/Pd membranes functions were shown to be 92.2% at 250 °C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Choi, Jungsu,Lee, Dongho,Lee, Kihee,Joo, Hyunjong Taylor Francis 2016 Desalination and water treatment Vol.57 No.2
<P>The purpose of this study is to remove high-concentration geosmin (GSM) by applying a granular-activated carbon (GAC) filter and a membrane filtration (MF) process injected with powdered-activated carbon (PAC). In this study, laboratory-scale experiments were conducted to (1) develop isotherm equations for GSM adsorption using PAC and GAC, (2) assess GSM adsorption competition by dissolved organic carbon (DOC), and (3) derive design factors for a pilot plant. In addition, the flux of the cross-flow-type pressurized MF was assessed at various PAC concentrations. Based on the results, a pilot plant was designed and operated from 14 July to 16 August 2013. The pilot plant operation achieved not only a stable treated water quality with an average GSM concentration of 10ng/L or less (removal efficiency: 99.5%), but also a treated water quality with an average DOC concentration of 0.5mg/L or less (removal efficiency: 91.7%) at the same time. From these findings, it was concluded that it may be possible (a) to meet the monitoring criteria for drinking water quality when high-concentration GSM is exposed, (b) to reduce the total amount of PAC inputs, and (c) to redress possible public complaints about compounds with unpleasant taste and odor.</P>