• Membrane Journal
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• v.16 no.4
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• pp.294-302
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• 2006

Silver polymer electrolytes are very promising membrane materials for the separation of olefin/paraffn mixtures. Olefin molecules are known to be transported through reversible complex formation with silver ions entrapped iii polymer matrix. However, they have poor long-term stability, which is very important fur the industrial application; the selectivity through the membrane decreases gradually with time mostly due to the reduction of silver ions ($Ag^+$) into silver nanoparticles ($Ag^0$). In this study, the stability of silver polymer electrolyte was investigated for poly(vinyl pyrrolidone) (PVP) and $AgBF_4$ system containing a surfactant, i.e. $C_{18}H_{35}(OCH_2CH_2)_{20}OH$ (Brij98) as a stabilizer. The reduction behavior of silver ions to silver nanoparticles in PVP was also investigated by atomic force microscopy (AFM) and UV-visible spectroscopy. It was found that the growth of silver nanoparticles was slower and selectivity of polymer electrolyte for propylene in propylene/propane was maintained longer time when Brij98 was added as a stabilizer.

• Journal of the Korean Chemical Society
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• v.43 no.1
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• pp.36-41
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• 1999

The adsorptive stripping voltammetric determination method of trace germanium (IV) using mercaptoacetic acid as a ligand was studied. Optimal conditions were found to be 0.25 M NaCl solution (pH 6.0) containing mercaptoacetic acid concentration of $5.0{\times}10^{-6}M$. The peak potential appeared at - 1.402 V vs. Ag/AgCl. Effects of sodium chloride concentration, mercaptoacetic acid concentration, and accumulation time for the complex of Ge(IV)-Mercaptoacetic acid on the peak current were studied. Amberlite IRC-718 chelating resin was applied to the separation of Ge(IV) from other metal ions.

• Journal of Microbiology and Biotechnology
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• v.29 no.11
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• pp.1841-1851
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• 2019

Garcinol, a well-known medicinal phytochemical, was extracted and isolated from the dried fruit rinds of Garcinia quaesita Pierre. In this study, garcinol has successfully used to reduce silver ions to silver in order to synthesize garcinol-capped silver nanoparticles (G-AgNPs). The formation and the structure of G-AgNPs were confirmed by UV-visible spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The antimicrobial activity of garcinol and G-AgNPs were investigated by well diffusion assays, broth micro-dilution assays and time-kill kinetics studies against five microbial species, including Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Candida albicans (ATCC 10231) and clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). The formation of G-AgNPs is a promising novel approach to enhancing the biological activeness of silver nanoparticles, and to increase the water solubility of garcinol which creates a broad range of therapeutic applications.

• Analytical Science and Technology
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• v.25 no.3
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• pp.159-163
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• 2012

A spectrofluorimetric method has been developed for the determination of free $CN^-$ in real samples with fluorescent safranine-O. When safranine-O interacts electrostatistically with $CN^-$, the fluorescent intensity of safranine-O is decreased. Several experimental conditions such as pH of the sample solution and the amount of safranine-O were optimized. $Ag^+$ interfered higher than any other ions. Interference of $Ag^+$ could be disregarded because $Ag^+$ was scarcely contained or mostly complexed with $CN^-$ in selected real samples. With this proposed method, the linear range of $CN^-$ was from 5.0 to 110 ng/mL and the detection limit of $CN^-$ was 2.9 ng/mL. For validating this technique, real samples (Cu, Ag, Au electroplating wastewater, and untreated wastewater in university and in sewage treatment plant) were used. Recovery yields of 91.5%~106.0% were obtained. Based on experimental results, it is proposed that this technique can be applied to the practical determination of free $CN^-$.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.579-587
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• 2015

To support the use of nuclear power as a sustainable electric energy generating technology, long-term supply of uranium is very important. The objective of this research is to investigate the use of new adsorbent material for cost effective uranium extraction from seawater. An activated carbon-based adsorbent material is developed and tested through an electrosorption technique in this research. Adsorption of uranium from seawater by activated carbon electrodes was investigated through electrosorption experiments up to 300 minutes by changing positive potentials from +0.2V to +0.8V (vs. Ag/AgCl). Uranium adsorption by the activated carbon electrode developed in this research reached up to 3.4 g-U/kg-adsorbent material, which is comparable with the performance of amidoxime-based adsorbent materials. Electrosorption of uranium ions from seawater was found to be most favorable at +0.4V (vs. Ag/AgCl). The cost of chemicals and materials in the present research was compared with that of the amidoxime-based approach as part of the engineering feasibility examination.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2926-2936
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• 2021

Rare-earth (RE) industries generate a massive amount of radioactive residue containing high thorium concentrations. Due to the fact that thorium is considered a non-economic element, large volume of these RE processed residues are commonly disposed of without treatment. It is essential to study an appropriate treatment that could reduce the volume of waste for final disposition. To this end, this research investigates the applicability of carbon-based adsorbent in separating thorium from aqueous phase sulphate is obtained from the cracking and leaching process of solid rare-earth by-product residue. Adsorption of thorium from the aqueous phase sulphate by carbon-based electrodes was investigated through electrosorption experiments conducted at a duration of 180 minutes with a positive potential variable range of +0.2V to +0.6V (vs. Ag/AgCl). Through this research, the specific capacity obtained was equivalent to 1.0 to 5.14 mg-Th/g-Carbon. Furthermore, electrosorption of thorium ions from aqueous phase sulphate is found to be most favorable at a higher positive potential of +0.6V (vs. Ag/AgCl). This study's findings elucidate the removal of thorium from the rare-earth residue by carbon-based electrodes and simultaneously its potential to reduce disposal waste of untreated residue.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.250-255
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• 2006

The synthesis and characterization of silver colloidal nanoparticles by chemical reduction of silver ions in aqueous $AgNO_3$ using sodium borohydride $(NaBH_4)$ as the reducing agent are described. The experimental conditions for aggregation and paricle size of nanosilver particles in water is investigated in terms of concentration of $NaBH_4$, reaction temperature, dropping rate of $AgNO_3$ and concentration of laponite. Stable nanosilver sol is obtained at three molar ratio of $NaBH_4/AgNO_3$ in conditions of without laponite. The size of nanosilver particles is increased as the reaction temperature is increased. The large size of nanosilver sol is obseved as the dropping rate of $AgNO_3$ is increased due to the aggregation of initial high local concentration of nanosilver particles. Stable nanosilver sol at high temperature $(>\;100^{\circ}C)$ can be prepared when laponite is used as protective colloid.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.499-505
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• 2018

We applied column experiments to investigate the environmental fate and transport of silver nanoparticles(AgNPs) in fully saturated conditions of porous media. These column experiments were performed to emphasize oxidation method with $H_2O_2$ concentration and acidic conditions. The mobility of AgNPs was decreased with the increasing ionic strength that the surface charge of AgNPs(zeta potential) was neutralized with the presence of positive ions of $Na^+$. Additionally, it was also affected due to that not only more increased aggregated size of AgNPs and surface charge of quartz sand. The decreased breakthrough curves(BTCs) of bisphenol-A(BPA) and $17{\alpha}$-ethynylestradiol(EE2) were removed approximately 35.3 and 40%. This is due to that endocrine disrupting chemicals(EDCs) were removed with the release of $OH{\cdot}$ radicals by the fenton-like mechanisms from acidic and fenton-like reagent presenting. This results considered that higher input AgNPs with acidic conditions is proved to realistic in-situ oxidation method. Overall, it should be emphasized that a set of column experiments employed with adjusting pH and $H_2O_2$ concentration in proved to be effective method having potential ability of in-situ degradation for removing organic contaminants such as BPA and EE2.

• Korean Journal of Materials Research
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• v.18 no.12
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• pp.678-682
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• 2008

This study investigates $Bi_2O_3$-$B_2O_3$-BaO-ZnO glass with variations of the $Co_3O_4$ content (0.25, 0.5, 1, and 2 wt%) and the interaction between transparent dielectric and Ag electrodes heat-treated at $500-560^{\circ}C$ for 30 min. The glass transition temperature, softening temperature and thermal expansion coefficient were $432^{\circ}C$, $460^{\circ}C$ and $81.4{\times}10^{-7}/^{\circ}C$, respectively. The transmittance of 0.25 wt% $Co_3O_4$ to which dielectric was added was highest and was decreased due to coloration with the addition of more than 0.25 wt%. However, without $Co_3O_4$, the transmittance of the transparent layer was decreased due to the formation of $Ba_5Bi_3$; however, the occurrence of the crystal phase decreased as a result of the addition of $Co_3O_4$. The amount of $Co^{2+}$ ions increased as the $Co_3O_4$ increased. With a maximum of $Co^{3+}$ ions, the highest transmittance was observed.

• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.1005-1008
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• 2006

The reaction of $AgClO_{4}$ with acyclic potential tridentate N,N,N',N',N''-pentamethyldiethylenetriamine (pmdeta) has given colorless crystals suitable for X-ray crystallography. The crystal structure ($P2_{1}$/n, a = 14.413(1) $\AA$, b = 25.270(2) $\AA$, c = 16.130(1) $\AA$, b = $103.012(1){^{\circ}}$, V = 5723.7(8) A$\AA^{3}$, Z = 4, R = 0.0349) has been solved and refined. Three silver(I) ions connect four pmdeta ligands to produce discrete complex of $[Ag_3(pmdeta)_4](ClO_4)_3$. A pmdeta ligand is bridged to three silver(I) ions, and three other pmdeta ligands are chelated to each silver(I) center in a tridentate mode. Thus, the product is a rare tri-nuclear silver(I) complex with two different chemical environments. $^{13}C$ NMR and $MAS\;^{13}$C NMR indicate that the tri-nuclear silver(I) complex is not rigid in solution. The contact angles and thermal analyses of the complex are measured and discussed.