• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.1
• /
• pp.131-137
• /
• 1998

A composite copper coated powder was generated by pressure hydrogen stripping copper from Kelex 100 solvent extractant in the presence of silica powder. Within the limitation of solvent extraction under constant conditions, both loading level and stripping rate were reproducible. The stripping copper kinetics are reduced from a divalent state to a metallic state and then deposited on the surface of the silica powder. Copper nucleates heterogeneously on the seed particles. They are giving an agglomerated and non - uniform powder.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.1
• /
• pp.23-28
• /
• 2011

This paper outlines extraction potential of tidal stream resources from the simplified channel in which flow is driven by a head difference between inlet and outlet. Energy extraction alters the flow within a simple channel, and extraction of 10% energy flux in a natural channel would give rise to a flow speed reduction of about 5.7%. If 20% of the undisturbed energy flux is extracted, the flow speed is reduced by 11.3%. The simple channel also suggests that extractable energy might be higher if flow speed reductions are considered acceptable.

• Advances in materials Research
• /
• v.9 no.4
• /
• pp.251-263
• /
• 2020

α-mangostin imprinted polymers have been synthesized by a non-covalent imprinting approach with α-mangostin as a template molecule. The α-mangostin molecularly imprinted polymers (MIPs) prepared by radical polymerization using methacrylic acid, ethlylene glycol dimethacrylate, benzoyl peroxide, and acetonitrile, as a monomer, crosslinker, initiator, and porogen, respectively. The template was removed by using methanol:acetic acid 90:10 (v/v). The physical characteristics of the polymers were investigated by Fourier Transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The rebinding studies were carried out by batch methods. The results exhibited that the MIPs was able to adsorb the α-mangostin at pH 2 and the contact time of 180 min. The kinetic adsorption data of α-mangostin performed the pseudo-second order model and followed the Langmuir isotherm model with the adsorption capacity of 16.19 mg·g-1. MIPs applied as a sorbent material in solid-phase extraction, namely molecularly imprinted solid-phase extraction (MISPE) and it shows the ability for enrichment and clean-up of α-mangostin from the complex matrix in medicinal herbal product and crude extract of mangosteen (Garcinia mangostana L.) pericarp. Both samples, respectively, which were spiked with α-mangostin gives recovery more than 90% after through by MISPE in all concentration ranges.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.2
• /
• pp.46-55
• /
• 2016

The kinetic analysis of a heavily aluminized cyclotrimethylene-trinitramine(RDX) is conducted using differential scanning calorimetry(DSC), and the Friedman isoconversional method is applied to the DSC experimental data. The pre-exponential factor and activation energy are extracted as a function of the product mass fraction. The extracted kinetic scheme does not assume multiple chemical steps to describe the complex response of energetic materials; instead, a set of multiple Arrhenius factors is constructed based on the local progress of the exothermic reaction. The resulting reaction kinetic scheme is applied to two thermal decomposition tests for validating the reactive flow response of a heavily aluminized RDX. The results support applicability of the present model to practical thermal explosion systems.

• Journal of Soil and Groundwater Environment
• /
• v.18 no.7
• /
• pp.18-24
• /
• 2013

The influences of various operating parameters on physico-chemical techniques were evaluated to remediate petroleum-contaminated sandy soil including S/L ratio, kinetic, and effect of soil particle size. The simple extraction using tap water removed only 20.6% of total petroleum hydrocarbon (TPH), and addition of NaOH enhanced the removal of TPH to approximately 30%. To meet the regulation levels, a surfactant, sodium dodecyl sulfate, was added, and the removal of TPH increased to 4 times. Probably, the carbonate minerals affected chemical aging and soprtion of petroleum, which inhibited the extraction of TPH. The soil with smaller particle size contained more TPH, and the removal of TPH was obstructed with smaller particle size. However, NaOH addition increased the removal of TPH in the smaller particles. The physico-chemical properties of soil influenced greatly the removal of petroleum even in sandy soil.

• Economic and Environmental Geology
• /
• v.32 no.1
• /
• pp.53-62
• /
• 1999

The possibility of heavy metal pollution by contaminated roadside soils was studied under controlled conditions. The soil samples from roadside and those from a retention pond consisting of settling particles were characterized by the XRD analyses and the sequential extraction experiments. Characterization by sequential extraction, for roadside soil indicates elevate total concentrations of heavy metals. The leaching behavior of the samples under different pH and time conditions were also studied. Differences between both types of samples result mainly from the buffering effect of carbonates, present in roadside soils and lacking from settling particles. Acid leaching of the settling particles is equivalent to the sum of FI+FII+FIII, while the amounts leached from roadside soil are lower probably from kinetic reasons. The buffering effects of carbonates were found to greatly delay the onset of the leaching reactions and the extent of dissolution in most metals except for Ca and Mn. The study of leaching kinetics at pH of 6.5 and 5 showed that Cd and Zn reached the maximum possible concentration within 3 days, while Pb did not show any sign of dissolution at both ph values. The absolute amounts of dissolved Cd and Zn increased by 7 to 9 times by decreasing the pH from 6.5 to 5, indicating slightly acidified rain may result in significant metal dissolution. As deduced from both sequential extraction and leaching experiments, the relative mobility of heavy metals is found to be : Mn=Cd>Zn>>Pb>Fe, in spite of large differences in heavy metal contents and localizations.

• Membrane and Water Treatment
• /
• v.7 no.3
• /
• pp.223-240
• /
• 2016

In this study, poly(vinyl-alcohol) and water insoluble ${\beta}$-cyclodextrin polymer (${\beta}$-CDP) cross-linked with citric acid, have been used as macrocyclic carrier in the preparation of polymer inclusion membranes (PIMs) for aniline (as molecule model) extraction from aqueous media. The obtained membranes were firstly characterized by X-ray diffraction, Fourier transform infrared and water swelling test. The transport of aniline was studied in a two-compartment transport cell under various experimental conditions, such as carrier content in the membranes, stirring rate and initial aniline concentration. The kinetic study was performed and the kinetic parameters were calculated as rate constant (k), permeability coefficient (P) and flux (J). These first results demonstrated the utility of such polymeric membranes for environmental decontamination of toxic organic molecules like aniline. Predictive modeling of transport flux through these materials was then studied using design of experiments; the design chosen was a two level full factorial design $2^k$. An empirical correlation between aniline transport flux and independent variables (Poly ${\beta}$-CD membrane content, agitation speed and initial aniline concentration) was successfully obtained. Statistical analysis showed that initial aniline concentration of the solution was the most important parameter in the study domain. The model revealed the existence of a strong interaction between the Poly ${\beta}$-CD membrane content and the stirring speed of the source solution. The good agreement between the model and the experimental transport data confirms the model's validity.

• Applied Biological Chemistry
• /
• v.21 no.2
• /
• pp.112-118
• /
• 1978

Xanthine oxidase from bovine thyroid glands was purified to apparent homogeneity when judged by analytical disc gel electrophoresis. The purification procedures include pancreatin digestion, butanol extraction, ammonium sulfate precipitation, calcium phosphate gel adsorption, ultrafiltration, calcium phosphate gel-cellulose column chromatography, gel filtration, preparative Sephadex G-25 column electrophoresis, and preparative polyacrylamide gel electrophoresis. The enzyme was enriched 1,000-fold. However, its specific activity was markedly low as compared with highly purified milk enzyme. Thyroidal xanthine oxidase exhibited a low specificity for substrates and electron acceptors. The kinetic properties of thyroid xanthine oxidase were found to be similar to those of the milk enzyme on the basis of Michaelis constants for common substrates.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.9
• /
• pp.1032-1041
• /
• 2004

In this study we decompose the 3-dimensional velocity field of isotropic turbulent flow into the coherent and the incoherent structure using the discrete wavelet. It is shown that the coherent structure, 3% wavelet modes, has 98% energy and 88% enstrophy and its statistical characteristics are almost same as the original turbulence structure. And it is confirmed that the role of the coherent structure is that it produces the turbulent kinetic energy at the inertia range then transfers energy to the dissipation range. The incoherent structure, with residual wavelet modes, is uncorrelated and has the Gaussian probability density function but it dissipates the kinetic energy in dissipation range. On the procedure, we propose a new but easy way to get the threshold by applying the energy partition percentage concept about coherent structure. The vorticity field extracted from the wavelet-decomposed velocity field has the same structure as the result of the precedent studies which decomposed vorticity field directly using wavelet. Therefore it has been shown that velocity and vorticity field are on the interactive condition.

• Applied Chemistry for Engineering
• /
• v.4 no.4
• /
• pp.672-682
• /
• 1993

2, 4-Heptadione(abbreviated to 24HTD) was synthesized from methylpropyl ketone and ethyl acetate with sodium amide, and the equilibrium and the kinetic characteristics of copper extraction by 24HTD-chloroform were investigated. Equilibrium constants such as the dissociation constant and the distribution coefficient of 24HTD and the stability constant of the 24HTD-Cu chelate were evaluated from the spectrophotometry, and the overall equilibrium constant of the extraction was also determined. The extracted species of the 24HTD-Cu chelate was found to be $CuR_2$ and the initial rate of the extraction of coupper by 24HTD in chloroform was expressed by $R_0=k[\bar{HR}]([Cu^{2+}]/[H^+])^{0.5}$.