• 한국생물공학회:학술대회논문집
• /
• 2003.04a
• /
• pp.611-614
• /
• 2003

The rheological properties of exopolysaccharide, p-KG03, produced by marine microalgae Gyrodinium impudicum strain KG03 had been studied. The intrinsic viscosity of this p-KG03 was calculated to 65.22 and 50.75 $d{\ell}/g$ using Huggins and Kramer equations (xanthan gum 24.41 and 24.03). Aqueous dispersions at p-KG03 concentrations ranging from 0.1 to 1.0 % (w/w) showed marked shear-thinning properties as Power-Law behavior. In aqueous dispersions of p-KG03 1.0 %, consistency index (K) and flow behavior index (n) were 2,172 and 0.52. The apparent viscosity and the influence of shear rate on different conditions as p-KG03 concentrations, pH, NaCl, $CaCl_2$ and temperature in aqueous solutions were measured. And p-KG03 had mixed with aqueous solutions of xanthan gum and gellan gum, and invested the change of mixed aqueous solution behavior.

• Fibers and Polymers
• /
• v.4 no.1
• /
• pp.27-31
• /
• 2003

A major concern in solvent extraction process is the loss of extractant into the aqueous phase due to its slight solubility in the aqueous phase. Similarly, in membrane extraction processes, extractant loss through extractant leakage from the membrane into the aqueous phase is also a concern. Several published membrane extraction studies using Aliquat 336 ai the extractant, have expressed this concern, but none has studied extractant leakage quantitatively. It is the authors' opinion that the extractant leakage should be considered at a technical parameter of a membrane. In our laboratory active progress has been made in using Aliquat 336 ‘entangled’ into the polymer membranes to remove heavy metal ions from wastewater samples. In this work, we studied the loss of Aliquat 336 from the point of view of its solubility in aqueous solutions. The results showed that the solubilities or Aliquat 3,36 in an aqueous phase acidified with 2 M HCI it about 0.1 g/100 m/ of the solution. This figure provides a useful guideline for evaluating the leakage of the Aliquatoat 336 extractant from the membranes.

• Journal of the Korean institute of surface engineering
• /
• v.43 no.4
• /
• pp.180-186
• /
• 2010

$TiO_2$ nanotubes were formed on Ti by anodizing in 1 M $H_3PO_4$ + 0.3 M HF and 0.1 M $NH_4F$ + 2% $H_2O$ in ethylene glycol, and their surface and cross-sectional morphologies were observed using FE-SEM as a function of anodizing time and applied voltage. The cross-section of the $TiO_2$ nanotubes was readily observed from the small pieces of nanotubes remaining near the scratch lines after scratching of the anodized surface. $TiO_2$ nanotubes was observed to grow faster and thicker in non-aqueous solution than in aqueous solution. Diameter of $TiO_2$ nanotubes was proportional to the applied voltage, irrespective of the type of the electrolyte, and it is recommended to use non-aqueous solutions for the preparation of larger diameter of $TiO_2$ nanotubes.

• Journal of the Korean Chemical Society
• /
• v.24 no.3
• /
• pp.209-217
• /
• 1980

The relative viscosities and osmotic coefficients of solutions of urea, 1,3-dimethyl-urea(DMU), acetamide(AA), and propionamide (PA) in dimethylsulfoxide(DMSO), water, methanol, and in ethanol have been measured at 25 and $45^{\circ}$C by viscometry and osmometry. Viscosity increment in nonaqueous solutions decreased with increasing of the partial molal volumes of the solutes, but in aqueous solution the result was inversed. Viscosity increment of aqueous solution was smaller than that of aqueous DMU solution, but that of nonaqueous urea solution was larger than that of DMU. Amides, however, showed similar viscosity increment in any solvent.Osmotic coefficients of aqueous solution of urea were larger than those of DMU. In the nonaqueous solutions urea exhibited larger deviation from Raoult's law than DMU. The results indicated that urea molecules break water-structure in water, self-associate in DMSO, and showed larger solute-solvent interaction in alcohols than DMU. It can be also confirmed that amides break alcohol structure to a greater extent than any other solutes.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.494-499
• /
• 2001

The present work investigates the possible use of fly ash for the removal of heavy metal ions from aqueous solutions. Batch experiments were conducted and the influences of metal concentration, pH, and fly ash concentration were investigated. Heavy metals used in these studies were zinc, lead and cadmium. Adsorption studies were done over a range of pH values (3-10) at $25^{\circ}C$ and heavy metal concentrations of 10-400 mg/L using fly ash concentrations of 10, 20 and 40 g/L. Experiments were also conducted without fly ash to determine the extent of heavy metal removal by precipitation. Kinetic and equilibrium experiments were performed and adsorption data were correlated with both Langmuir and Freundlich adsorption models. The results indicate that fly ash can be used as an adsorbent for heavy metals in the aqueous solutions, yet the degree of removal depends on the pH.

• Biomolecules & Therapeutics
• /
• v.1 no.1
• /
• pp.31-36
• /
• 1993

To evaluate the feasibility of transmucosal delivery of methionine enkephalin analog, [$D-Ala^2$]-me-thionine enkephalinamide (YAGFM), the influence of pH, temperature, ionic strength and initial peptide concentration on the physicochemical stability of YAGFM in aqueous buffered solutions were investigated using a stability-indicating HPLC method. The degradation of YAGFM followed the pseudo-first-order kinetics. From the pH-rate profile, the maximum stability of YAGFM was shown to be at the pH of about 5.0. The halflife for the degradation of YAGFM was found to be 181.3 days at pH 5.0 and $37^{\circ}C.$ Arrhenius plots of the data obtained at 25~$45^{\circ}C$ were reasonably linear with a correlation coefficient greater than 0.99, and the activation energy was calculated to be 8.9 kcal/mole. A higher ionic strength and/or a higher peptide concentration in buffered solutions retarded the degradation of YAGFM.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.4 no.4
• /
• pp.241-247
• /
• 2000

This paper reports on an experimental study of the absorption of COS in a secondary amine diethanolamine. The primary objectives were to investigate an analogy between $N_2$O and COS, thereby allowing an estimation of the physical solubility and diffusivity of the sulfur gases in the reacting amine solutions. The solubilities and diffusivities of $N_2$O and COS in 5~25% aqueous polyethylene glycol at $25^{\circ}C$ were measured. The results appeared to verify the use of an $N_2$O-COS analogy for estimating the solubility and diffusivity of COS in aqueous solutions of alkanolamines up to an approximate 25 weight % concentration. The mean deviation of the $N_2$O analogy relative to the measured solubilities was 3.7%, and the mean deviation between the analogy and the measured diffusion coefficients using the experimental values for Hcos/PEG was 14.6%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.6
• /
• pp.481-485
• /
• 2012

ZnO nanowires were synthesized by hydrothermal technique. Prepared synthesis aqueous solutions were preserved by preheating in autoclave type synthesis equipment with various preheating time of 1 h difference. ITO-coated corning glass substrates deposited with AZO seed layers were then inserted in the preheated synthesis aqueous solutions and ZnO nanowires were grown for 180 min at $90^{\circ}C$. Density, length and aspect ratio of the grown ZnO nanowires were investigated. Composition, structural and optical properties of the grown ZnO nanowires were analyzed. Characteristics of the ZnO nanowires were comparatively studied in relation with $Zn^{2+}$ ion concentration measured directly after the preheating of synthesis aqueous solution.

• Journal of ILASS-Korea
• /
• v.20 no.1
• /
• pp.20-27
• /
• 2015

Urea-SCR which is one of the aftertreatment technologies for reducing the NOx emission is widely used. An experimental study was performed to investigate urea decomposition under various thermo-fluid conditions, with different temperatures and velocities of inflow gas, and urea solution quantities. 40 wt. % aqueous urea solutions were used in this study. The inflow gas conditions were similar to the exhaust conditions of a large marine engine. The spray performance of urea solution injector was identical under all experimental conditions. The conversion efficiency of $NH_3$ was larger than that of HNCO under all experimental conditions, unlike for the theoretical thermolysis reaction.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3391-3398
• /
• 2013

The carboxylated multiwall carbon nanotubes (MWCNT-COOH) and functionalized with isatin derivative (MWCNT-isatin) have been used as efficient adsorbents for the removal of lead (Pb) from aqueous solutions. The influence of variables including pH, concentration of the lead, amount of adsorbents and contact time was investigated by the batch method. The adsorption of the lead ions from aqueous solution by modified MWCNTs was studied kinetically using different kinetic models. The kinetic data were fitted with pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The sorption process with MWCNT-COOH and MWCNT-isatin was well described by pseudo-second-order and pseudo-first-order kinetics, respectively which it was agreed well with the experimental data. Also, it involved the particle-diffusion mechanism. The values of regression coefficient of various adsorption isotherm models like Langmuir, Freundlich and Tempkin to obtain the characteristic parameters of each model have been carried out. The Langmuir isotherm was found to best represent the measured sorption data for both adsorbent.