• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.38-44
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• 2002

Dispersion stability of nano-sized rutile TiO$_2$powder with acicular typed primary particle produced by homogeneous precipitation process at low temperatures was studied in aqueous and non-aqueous media in the presence of various electrolytes. The zeta potential measurements have shown that the addition of electrolytes to aqueous and non-aqueous dispersion media leads to charge reversal on TiO$_2$particle surface. The electrostatic repulsive forces acting on between TiO$_2$particles dispersed in non-aqueous media were found to be significantly greater than that in aqueous media, which relate closely to the physical properties of the organic solvents, such as viscosities and dielectric constants. The pH values, the concentration of electrolytes and the valence of the ions have changed greatly the surface potential of TiO$_2$ particles and have governed the dispersion behavior of TiO$_2$particles virtually.

• Journal of Adhesion and Interface
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• v.18 no.3
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• pp.109-117
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• 2017

Poly(N-vinyl carbazole) (PVK) homopolymer, poly(4-vinylpyridine) (PVP) homopolymer, and PVK-b-PVP block copolymer were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and the polymers were used to prepare non-aqueous graphene dispersions with four different solvents, ethanol, N-methyl-2-pyrrolidone (NMP), dichloromethane (DCM), and tetrahydrofuran (THF). $^1H-$ and $^{13}C-NMR$ spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) were carried out to confirm the chemical structure of the polymers. Stability of graphene dispersions was measured by on-line turbidity measurement. Time-dependent Turbiscan Stability Index (TSI) values were interpreted in terms of surface tension (${\sigma}$) and solubility parameter (${\delta}$) among solvents, polymers, and graphene. It was confirmed that the solubilities of polymer and surface tension between solvent and graphene affected the dispersion stability of graphene. PVK-b-PVP block copolymer could effectively maintain the low TSI values of graphene dispersions in ethanol and THF, which have been known as poor solvents for graphene dispersions. It can also be noted that DCM shows good dispersion stability comparable to NMP, which has been known as the best solvent for graphene dispersion.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.E
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• pp.27-40
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• 1998

The solubility characteristics of organic compounds were studied in terms of the extraction efficiency as a function of the polarity of the organic solvent, and the acidity of water in urban aerosol samples collected in University of East Anglia (UEA), Norwich, England. The extraction efficiency of organic compounds were evaluated with respect to the organic carbon, -nitrogen and -hydrogen by means of a wide range of solvent which include polar and nonpolar organic solvents as well as acids and alkaline water. In addition, after being dissolved in aqueous solution, the aqueous chemistry of organic compounds were studied in terms of the organic metal complexes in aerosol, which were studied with oxalic acid, copper, and zinc. The results of this study indicate that solubility characteristics of organic compounds depend on the polarity of the solvents and the acidity of the solvents. In particular, some organic compounds are water soluble, even though they are much smaller than acetone soluble fractions. In the comparison between polar organic solvent extraction and non- polar organic solvent extraction, it can be thought that significant fraction of organic compounds analysed in the aerosol samples, are polar organic compounds because of the higher extraction efficiencies of organic compounds in polar organic solvent extraction than in nonpolar organic solvent extraction. Regarding the study of the oxalic -metal complexes, it can be thought that most oxalic acids are present in the form of oxalic -copper complexes in the aerosols collected at UEA.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.324-331
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• 2014

The dispersion characteristics of AlN-4.5 wt% $Y_2O_3$ powder mixture by various dispersants were investigated in ethanol and methyethly-ketone (MEK) solvents. In general, the cationic polymer dispersants demonstrated superior dispersion of the powder as compared to the non-ionic ester-type dispersants or anionic phosphate-ester-based ones. The dispersion performance of the cationic polymer dispersants was sensitive to the type of solvent. An anhydric maleic-acid-based graft copolymer dispersant, AFB-1521, demonstrated a very good dispersion capability in ethanol but exhibited a much inferior dispersion in MEK. On the other hand, the dispersion of the powder mixture was very good with a phosphate-ester-based block polymer dispersant, BYK-111, in MEK solvent, while dispersionwas much degraded in ethanol.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.685-689
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• 2000

The complexation reaction between Pb2+,TI and Cd2+ions and macrocyclic ligands, 18-crown-6 ( 18C6) and dibenzo- 18-crown-6 (DB 18C6), was studied in dimethylsulfoxide (DMSO)-nitromethane (NM) and dimethyl-formamide (DMF)-nitromethane binary system s by square wave polarography (SWP) technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the Iigand concentration. In most cases, the stability constants of complexes increase with increasing amounts of the nitromethane in mixed binary solvents used in this study. The complexes formed between 18C6 and DB18C6 and these metal cations in all cases had a stoichiometry of 1 : 1. The results obtained show that there is an inverse relationship between the formation constant of complexes and the donor number of solvents based on a Gatmann donocity scale and the stability constants show a high sensitivity to the composition of the mixed solvent systems. A linear behavior was observed for variation of log Kf of I8C6 complexes vs the composition of the mixed solvent systems in NM/DMSO and NM/DMF,but a non-linear behavior was observed in the case of DB 18C6 complexes in these binary systems. In most of the systems investigated, the Pb2+ cation forms a more stable complex with the 18C6 than other two cations and the order of selectivity of this Iigand for cations is: Pb2+ > TI+,Cd2+.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.320-325
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• 2007

Nickel powders were prepared from an aqueous nickel acetate solution and hydrazine hydrate using diethanolamine as the nonaqueous organic solvent in the conventional and microwave synthetic method. It was investigated that microwave non-thermal effect and synthetic condition affect the preparation of nickel powders by means of X-ray diffractometry, scanning electron microscopy, thermal gravymetry analysis, and X-ray photoelectron spectroscopy analysis. Compared with the conventional synthetic method, less of aggregation, smaller particle size, and more uniform distribution of particle size were obtained in the microwave synthetic method due to the non-thermal effect of microwaves.

• Korean Membrane Journal
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• v.1 no.1
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• pp.50-58
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• 1999

Symmetric asymmetric and composite perfluoropolymer membranes made with HYFLON AD have been prepared and evaluated. Porous and non porous symmetric membranes have been prepared by solvent evaporation with various processing conditions. Non-contact atomic force microscopy (AFM) was used to investigate the membrane morphology in air. Analysis of the images gave quantitative imformation on the surface pore strcture in particular on the pore size distributin. Possible useful uses of porous membranes are envisaged in the field of gas-liquid separations such as membrane contactors (MSc) Molecular Dynamics(MD) simulations structure of HYFLON AD 60X copolymer supporting these results are also reported. Amorphous perfluoropolymer membranes appears to be ideal other than in MCs when separation processes have to be performed in hostile environments i.e. high temperatures and aggressive non-aqueous media such as chemicals and solvents. In these cases HYFLON AD mem-branes can exploit the outstanding resistance of perfluoropolymers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.2
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• pp.114-119
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• 2003

This study is to remove several organic pollutants from wastewater by non-dispersive membrane solvent extraction technique. The distribution coefficients of several solvents were determined and the experimental system was operated counter-currently and cocurrently with respect to the aqueous phase and solvent. In these experiments, as the flow rate of aqueous solution inclosed, due to being shortened contact time to solvent, the rate of removal of organic pollutants decreased and as the flow rate of solvent increased, the rate of removal increased. Meanwhile, the rate of removal of organic pollutants for the countercurrent flow system was higher than that for the occurrent flow system.

• Journal of Life Science
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• v.27 no.11
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• pp.1381-1392
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• 2017

This review described solvent-tolerant lipases and their potential industrial, biotechnological and environmental impacts. Although organic solvent-tolerant lipase was first reported in organic solvent-tolerant bacterium, many organic solvent-tolerant lipases are in not only solvent-tolerant bacteria but also solvent-intolerant bacterial and fungal strains, such as the well-known Bacillus, Pseudomonas, Streptomyces and Aspergillus strains. As these lipases are not easily inactivated in organic solvents, there is no need to immobilize them in order to prevent an enzyme inactivation by solvents. Therefore, the solvent-tolerant lipases have the potential to be used in many biotechnological and biotransformation processes. With the solvent-tolerant lipases, a large number insoluble substrates become soluble, various chemical reactions that are initially impossible in water systems become practical, synthesis reactions (instead of hydrolysis) are possible, side reactions caused by water are suppressed, and the possibility of chemoselective, regioselective and enantioselective transformations in solvent and non-aqueous systems is increased. Furthermore, the recovery and reuse of enzymes is possible without immobilization, and the stabilities of the lipases improve in solvent and non-aqueous systems. Therefore, lipases with organic-solvent tolerances have attracted much attention in regards to applying them as biocatalysts to biotransformation processes using solvent and non-aqueous systems.

• Archives of Pharmacal Research
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• v.17 no.3
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• pp.175-181
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• 1994

The solid-phase extraction (SPF) with subsequent tert-butyldimethylsilyl (TBDMS) derivatization was investigated for the rapid profiling and screening of various carboxylated non-steroidal antiinflammatory drugs (NSAIDs) simultaneously in biological fluid samples. Compared to the conventional SPF in adsorption mode using Chromosorb 102, Chromosorb 107, Carbopak B and Thermosorb, the SPF in partition mode using Chromosorb P as the adsorbent, and ethyl acetate/methylene chloride as the eluting solvents provided hightest overall recovenies of the NSAIDs from aqueous solutions with good precision. The solid-phase extracted NASIDs were silylated with N-methyl-N-(tert-butyldimethylsily)trifuoroacetamide to TBDMS derivatives and directly analyzed by capillary gas chromatography and gs chromatography-mass spectrometry. The usefulness of the present method was examined for the profilling and screening of saliva, serum and urine samples for various NSAIDs simultaneously.