• Resources Recycling
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• v.13 no.2
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• pp.24-32
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• 2004

Solvent extraction equilibria of Gd with PC88A from chloride solutions were analyzed by considering chemical equilibria. phase equilibria, mass and charge balance equations. The following solvent extraction reaction and equilibrium constant were evaluated from the experimental data performed in this study. $Gd^{3+}$ $+2H_2$$A_2$,$or=GdA_3$HA.or+3 $H^{+}$ , K=3.3 A procedure was suggested to calculate the initial concentration of chloride ion from initial pH and initial concentration of Gd. By applying ionic equilibria, the distribution of Gd complexes with Gd and HCl concentration was obtained. The predicted distribution coefficients of Gd agreed well with the experimental results.

• Resources Recycling
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• v.13 no.4
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• pp.39-45
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• 2004

Solvent extraction experiments of Nd from chloride solution were studied with PC88A. Solvent extraction reaction of Nd with PC88A and the equilibrium constant were evaluated from the extraction experimental data and extraction conditions. Nd$aq^{3+}$ + 1.5 $H_2$$A_2$,org = $NdA_3$,org + 3H/sun $aq^{+}$ , K=0.25 The predicted distribution coefficients of Nd agreed well with the experimental results. The effect of saponification of PC88A on the extraction of Nd and on the change of equilibrium pH was investigated. Saponified PC88A present as a monomer in the organic reaction and enhanced the distribution coefficient of Nd. The initial extraction conditions had a great effect on the equilibrium pH.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1163-1168
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• 1998

Fish tissues were spiked with organophosphorus pesticides (OPPs), mixed with a celite as a drying agent, and dynamically extracted with pure $CO_2$ or modified $CO_2$ for 10 min at different extraction temperatures, pressures and $CO_2$ flow rates. Recoveries of OPPs spiked in jacopever increased with the decrease of extraction temperature and pressure, and decreased with the increase of $CO_2$ flow rates. Modified $CO_2$ extractions with 10% methylene chloride showed a slight increase in the recoveries over pure $CO_2$ extraction. Quantity of fish tissues had great effect on their extraction efficiencies. Recoveries of OPPs were $66.7{\sim}86.3%$ for jacopever, $56.2{\sim}79.2%$ for yellow tail, $57.6{\sim}77.8%$ for blanquillo, $84.2{\sim}96.3%$ for sardine, $74.6{\sim}83.6%$ for mackerel. Application of supercritical carbon dioxide extraction offers an attractive alternative to the use of organic solvents for extraction of pesticide residues from fish tissues.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.109-116
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• 2017

The present study concerns quantitative assessment of chloride extraction, repassivation and structural behavior of concrete. Concrete specimen ($160{\times}160{\times}1000mm$) was fabricated with 3 steel bar located in the middle with 20 mm of the cover depth, containing 5.0% of chloride to accelerate corrosion process, then to be subjected to electrochemical treatment. The current density accounted for $750mA/m^2$ at 2, 4 and 8 weeks. As a result, it was found that an increase in the duration of the treatment resulted in an increase in the chloride extraction, accounting for 64.7-83.7% for the specimen at 8 weeks treatment. It implies that a portion of bound chlorides would turn free to be removed, considering the binding capacity of cement about 50-60% to total ones. Even after the treatment, the corrosion was still active; the corrosion rate was $6.5mA/m^2$ and 330 mV vs. SCE in the potential. For structural behavior, the maximum load was increased by corrosion on the steel bars, which was subsequently lowered by the treatment, but still higher than for control.

• Korean Journal of Environmental Agriculture
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• v.16 no.3
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• pp.239-244
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• 1997

To develope more effective extraction methods for paraquat in soil, some modification methods were accomplished in two different types of soil. For extraction of tightly bound-paraquat, conc. HCl 70ml were added with different shaking times, and then $H_2SO_4$ reflux were performed for an hour. In this case, 60 minutes shaking were optimum and recovery were increased more $1.09{\sim}1.50$ folds(84.0% in high clay contents soil, but 96.7% in low clay contents soil) and the long-time consuming step, filtration were easily done, with decreasing filtration time were shorter 4.6 folds(ca. $11{\sim}14min.$). than general paraquat analytical method(ca. $55{\sim}65min.$). And only $H_2O_2$ digestion with different volume and refluxing time resulted in recovery increasing. Nevertheless, considering analyst's safety, 30ml of $H_2O_2$ addition and 30 minutes reflux were regarded as optimum condition. Although, Kjeldahl digestion with $H_2O_2$ showed relatively high recovery, it is not significant statistically. For extraction of loosely bound-paraquat, 0.01, 0.1, 1.0, 10.0M of $NH_4Cl$ and of $CaCl_2$ compared with $1.5{\sim}24hr$ of different shaking time. There were no loosely bound residues of paraquat.

• Journal of the Korean Society of Tobacco Science
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• v.28 no.2
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• pp.83-93
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• 2006

The aim of this study is to develop a simple and rapid field method for the determination of chloride content in tobacco green or cured leaves. To set up a practical process, several factors such as the proper sampling position of each leaf, the size of leaf lamina pieces for blending, the substitution of deionized water fur the extracting solution, 0.1N $HNO_3$, the submerging durations before blending, and the standing times before measuring were studied using flue-cured and burley tobacco with a stable and reproducible Chloride Meter, KRK CL-2Z. From the results, chloride contents of tobacco leaves could be analyzed with the Chloride Meter(CL-2Z) using the suspension of 14 mm diameter leaf disks after soaking in distilled water for 30 min., blending with a mini-blender for 30 seconds. The chloride contents measured in this way showed highly significant correlations with ones by the conventional potentiometric method using an ion meter-chloride electrode and $AgNO_3$ titration. In our method, the procedures such as drying, powdering and weighing samples, and using chemical reagents for extraction (0.1N $HNO_3$) and titration(0.028N $AgNO_3$) could be eliminated. These results suggest that the newly constructed method using the Chloride Meter is more efficient to determine the chloride content of tobacco leave in comparison with the one by the Ion $Meter:AgNO_3$ titration.

• Analytical Science and Technology
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• v.25 no.6
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• pp.395-401
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• 2012

This study presents a method for the quantitative analysis of residual vinyl chloride monomer (VCM) in PVC products. In elution solvent, the extraction efficiency was similar by ethanol, THF, and acetone, but using n-hexane, it indicated relatively low extraction efficiency. Measuring VCM in the pulverized PVC samples, it showed reasonable results in both the direct injection method and headspace method with GC/MS. Regarding analysis of VCM in the intermediate sponge samples, five laboratories showed good results, and from the results, it was considered that VCM quantitative method in this study was reliable.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.289-297
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• 2022

Deterioration in durability of structures due to the steel corrosion is difficult to determine whether or not corrosion is initiated and how much propagated, and moreover, repair and maintenance are not easy to deal with. Therefore, preventive treatments can be the best option to avoid the deterioration. Various methods for preventing corrosion of steel, such as electrochemical treatments, anti-corrosion agents and steel surface coatings, are being developed, but economic and environmental aspects make it difficult to apply them to in-situ field. Thus, the purpose of this study was to improve corrosion resistance by using CA-based clinker that are relatively simple and expected to be economically profitable Existing CA-based clinkers had problems such as flash setting and low strength development during the initial hydration process, but in order to solve this problem, CA clinker with low initial reactivity were used as binder in this study. The cement paste used in the experiments was replaced with CA₂ clinker for 0%, 10%, 20%, and 30% in OPC. And the mixture used in the chloride binding test for the extraction of water-soluble chloride was intermixed with Cl- 0.5%, 1%, 2%, and 3% by weight of binder content. To evaluate characteristic of hydration heat evolution, calorimetry analysis was performed and simultaneously chloride binding capacity and acid neutralization capacity were carried out. The identification of hydration products with curing ages was verified by X-ray diffraction analysis. The free chloride extraction test showed that the chlorine ion holding ability improved in order OC 10 > OC 30 > OC 20 > OC 0 and the pH drop resistance test showed that the resistance capability in pH 12 was OC 0 > OA 10 > OA 20 > OA 30. The XRD analyses showed that AFm phase, which can affect the ability to hold chlorine ions, tended to increase when CA₂ was mixed, and that in pH12 the content of calcium hydroxide (Ca(OH)₂), which indicates pH-low resistance, decreased as CA₂ was mixed

• Journal of the Korean Chemical Society
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• v.30 no.5
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• pp.465-474
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• 1986

The solvent extraction and cleanup processes for the simultaneous gas-liquid chromatographic determination of 11 kinds of organophosphorous pesticide residues in crops were investigated. The extracts dissolved with acetone were partitioned with petroleum ether after adding saturated NaCl solution. Evaporated the partitioning solvent, the residue was dissolved in methylene chloride and eluted through mixed adsorbent (1 : 2 : 4 of activated carbon, magnesia and diatomaceous earth) with methylene chloride as an eluent. The pesticides recovered were 82∼105% and the impurities were effectively removed.

• Resources Recycling
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• v.19 no.3
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• pp.45-51
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• 2010

Solvent extraction behavior of Sn(IV) from hydrochloric acid solution was investigated using TBP(Tri-butyl Phosphate) as an extractant. The experimental parameters, such as the concentration of HCl solution, chloride ions, extractant, and Sn were observed. Experimental results showed that the extraction percent of Sn was increased with increasing the hydrochloric acid and chloride ion concentration. More than 98% of Sn was extracted in 7.0 M HCl by 10% TBP. The optimum extraction stages of Sn for continuous extraction process was theoretically calculated by analysizing the McCabe-Thiele diagram. Stripping of Sn from the loaded organic phases can be accomplished by NaOH as a stripping reagent effectively and 99.3% of Sn was stripped by 2.0M NaOH solution.