• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.479-483
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• 2018

Our group reported the thermal decomposition of R-22 ($CHClF_2$) refrigerants by nitrogen thermal plasma in previous studies. However, it was proposed that the wastewater generated from the end part of the process contains high concentration of fluoride ion which is a component of R-22. The additional post-treatment process to neutralize the $F^-$ ions in the wastewater was investigated in this study. The wastewater generated through the decomposition of R-22 with the same procedure in the previous work was treated using the neutralizer, $Ca(OH)_2$, and the atmospheric pressure plasma jet (APPJ) independently as a post-treatment process. Wastewater samples were collected directly after the treatment for ion-chromatography analysis to trace the change of the concentration of $F^-$ ion in the wastewater. The fluoride concentration in the wastewater showed the highest value when the single water was used as a neutralizer, and the concentration of fluoride in the wastewater was dramatically reduced when the post-treatments were performed.

• Analytical Science and Technology
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• v.29 no.5
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• pp.219-224
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• 2016

불산 중 극미량 음이온의 고상추출과 이온크로마토그래프를 이용한 고감도 분석법이 개발되었다. 불산 중 불소이온이 고상에 의해 제거하였고 이어서 음이온 (F⁻, CH₃COO⁻, Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻)들이 이온크로마토그래프를 이용하여 연속적으로 분리하였다. 고상 추출법에 영향을 주는 각 인자들 (흡착제의 선택, 시료의 부피 및 pH, 용출 용액과 용출용액의 부피)을 결정하였으며 그 결과 흡착제로서 Oasis WAX 컬럼이 가장 우수하였고 1.0 mL의 시료부피, 용출용액으로 50 mM 초산암모늄염 5 mL가 분리능에서 가장 우수하였다. 개발한 방법에 의한 음이온 (Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻)들의 방법검출한계는 25 % 불산용액 (w/w) 중에 0.04~0.30 µg/L의 범위를 보였고 정밀도는 20.0와 40.0 µg/L의 농도에서 5 % 이내를 보였다. 한 제조회사에 의한 25 % 불산 중 음이온의 4.2에서 47.5 µg/L의 범위로 모두 검출되었다. 이 방법은 시험절차가 간단하고, 재현성 및 감도가 좋아서 반도체회사에서 불산 중 음이온 불순물을 정도 관리하는데 매우 유용한 방법이 될 것으로 판단된다.

• Membrane Journal
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• v.26 no.2
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• pp.97-107
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• 2016

This study was carried out to prepare a heterogeneous cation exchange membrane by mixing polyvinylidene fluoride (PVDF), commercial cation exchange resin and sulfonated poly(phenylene oxide)(SPPO) in order to propose an optimum condition for the preparation, and to compare its properties with commercial membrane. Study results show that the ion exchange capacity and electrical resistance were outstanding when the ratio of polymer matrix was less than 30% comparing between PVDF-IER, PVDF-SPPO and PVDF-SPPO-IER. The tensile strength was confirmed that seemed a hard look was five times greater compared to the commercial heterogeneous membrane, despite the weak durability of PVDF resin. Therefore, when chemical and mechanical properties are considered, the optimum mixing ratio between PVDF, IER and SPPO was 30 : 70, at which electric resistance was measured as $3{\sim}5{\Omega}{\cdot}cm^2$, ion exchange capacity as 0.6~1.0 meq/g, while mechanical strength was in a range of $12{\sim}15kgf/cm^2$.

• Journal of Industrial Technology
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• v.42 no.1
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• pp.7-12
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• 2022

High nickel layered oxide cathodes are gaining increasing attention for lithium-ion batteries due to their higher energy density and lower cost compared to LiCoO₂. However, they suffer from the formation of residual lithium on the surface in the form of LiOH and Li₂CO₃ on exposure to ambient air. The residual lithium causes notorious issues, such as slurry gelation during electrode preparation and gas evolution during cell cycling. In this review, we investigate the residual lithium issues through its impact on cathode slurry instability based on deformed polyvinylidene fluoride (PVdF) as well as its formation and reduction mechanism in terms of inherently off-stoichiometric synthesis of high nickel cathodes. Additionally, new analysis method with anhydrous methanol was introduced to exclude Li⁺/H⁺ exchange effect during sample preparation with distilled water. We hope that this review would contribute to encouraging the academic efforts to consider practical aspects and mitigation in global high-energy-density lithium-ion battery manufacturers.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3031-3033
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• 2009

A new colorimetric anion sensor 1 has been synthesized based on both Fat brown RR dye and a nitrophenyl group. This new receptor 1 could recognize the presence of fluoride ion effectively and selectively by the change of color of solution. In addition, receptor 1 shows higher affinity for acetate, dihydrogenphosphate, and hydrogensulfate than the other anions such as chloride, bromide, iodide, perchlorate, and nitrate in acetonitrile.

• Journal of the Korean Chemical Society
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• v.27 no.6
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• pp.411-418
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• 1983

The effects of existing anions in hydrofluoric acid solutions, $F^-$ and $HF_2$on the extraction of methylene blue-$BF_4^-$ ion-pair into 1,2-dichloroethane have been investigated by spectrophotometry. The absorbance of the extracted ion-pair is found to be independent of $F^-$ion up to $10^{-2}$ molar concentration, which implies that $F^-$ion dose not directly interfere with the extraction. However, $HF_2^-$ ion competes with $BF_4^-$ion for methylene blue and the extraction constant for methylene blue-H$F_2$ion-pair is calculated to be 8.5 at $25^{\circ}C$.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.473-479
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• 2016

We report a highly selective and sensitive 200 MHz Surface Acoustic Wave (SAW) sensor that can detect cyanide ion in aqueous solution using surface immobilized thioester molecules in combination with gold nanoparticles (AuNPs). To construct the sensor device, a monolayer of thioester compound was immobilized on the SAW sensor surface. At the sensor surface, hydrolysis of thioester group by nucleophilic addition of cyanide occurred and the resulting free thiol unit bound to AuNP to form thiol-AuNP conjugate. For the signal enhancement, gold staining signal amplification process was introduced subsequently with gold (III) chloride trihydrate and reducing agent, hydroxylamine hydrochloride. The SAW sensor showed a detection ability of $17.7{\mu}M$ for cyanide in aqueous solution and demonstrated a saturation behavior between the frequency shift and the concentration of cyanide ion. On the other hand, our SAW sensor had no activities for other anions such as fluoride ion, acetate ion and sulfate ion, moreover, no significant interference observed by other anions. Finally, all the experiments were carried out in-house developed sensor and fluidics modules to obtain highly reproducible results.

• Membrane Journal
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• v.32 no.6
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• pp.486-495
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• 2022

This study presents the improved recovery efficiency of rare metal ions through the modified separation membrane wettability and hydrogen ion permeation in the anion exchange membrane (AEM) under the recovery process of combined electrodialysis and solvent extraction. Specifically, the wettability of the separator was enhanced by hydrophilic modification on one separator surface through polydopamine (PDA) and lipophilic modification on the other surface through SiO₂ or graphene oxide (GO). In addition, the modified surface of AEM with polyethyleneimine (PEI), PDA, poly(vinylidene fluoride) (PVDF), etc. reduces the water uptake and modify the pore structure for proton ions generation. The suppressed transport resulted in the reduced hydrogen ion permeation. In the characterization, the surface morphology, chemical properties and composition of membrane or AEM were analyzed with Scanning Electron Microscopy (SEM) and Fourier Transform-Infrared Spectroscopy (FT-IR). Based on the analyses, improved extraction and stripping and hydrogen ion transport inhibition were demonstrated for the copper ion recovery system.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.327-328
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• 2005

Trace anions in high-sulfate wastewater from mainly derelict mines were determined by ion chromatography with on-line preconcentration and preelution technique. As the sample was preconcentrated and more strongly held ions were preeluted to the principal separation system, this approach was highly effective in removing large concentration of sulfate in high-sulfate wastewater. With this practical on-line preelution treatment, the peaks of fluoride and chloride showed good resolution even when the sulfate concentration was as high as 2000 mg/L and the analyzed total metal concentration was above 500 mg/L.

• Journal of the Korean Applied Science and Technology
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• v.32 no.4
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• pp.718-723
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• 2015

For the fabrication of the Si negative electrode in Li-ion batteries (LIBs) containing the cross-linking polymer binder, in this work, the urethane acrylate (UA) oligomer was synthesized via a simple synthetic process. The cross-linked poly(urethane acrylate) (CPUA)/carbone black (CB)/Si composite (CPUA/CB/Si composite) was fabricated through reactions between their reactive vinyl segments in the UA oligomer. Interestingly, the CPUA/CB/Si composite showed better cycle performance than the poly(vinylidene fluoride) (PVdF)/CB/Si composite (PVdF/CB/Si composite) and the polyurethane (PU)/CB/Si composite (PU/CB/Si composite). The CPUA/CB/Si composite had the best lithiation of about $2586mAh\;g^{-1}$. The UA oligomer showed a good compatibility with the electrode materials and current collector after and before a curing process.