• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.264-267
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• 2005

플럭 형성 비소 오염토양에 대한 토양세척기법의 적용성 실험결과, 세척용액 100 mM과 500 mM의 농도에서 대상 토양에 대한 비소 용출량은 수산화나트륨이 염산보다 높은 효율을 보였으며, 농도 1000 mM의 경우에는 염산이 비교적 우세한 세척효율을 보였다. 토양오염공정시험법에 의한 세척후 토양내 잔류비소 농도의 경우, 염산이 수산화나트륨과 비슷하거나 다소 우세함을 알 수 있었다. 세척 대상 토양의 Cut-off size limit을 선정하여 토양세척시 생성되는 플럭을 제거하지 않고 반복 세척한 결과, 수산화나트륨의 농도 200 mM은 1000 mM에 비하여 잔류된 비소량이 비슷하거나 비교적 높았으며, 2가지 농도에 대하여 총 5회 반복 세척한 토양의 비소 농도는 토양환경보전법의 가지역 우려기준 농도인 6 mg/kg에 근접한 결과를 보였으나, 염산의 경우 총 5회 세척시 비소의 농도가 약 9 mg/kg으로 비소 잔류량이 보다 큼을 알 수 있었다. 플럭을 제거한 후 반복 세척시 수산화나트륨의 농도 1000 mM이 200 mM에 비하여 토양 세척효율이 증가하였으며, 1000 mM로 5회 세척시 잔류비소 농도가 가지역 우려기준 농도에 근접한 약 6.7 mg/kg이었고 염산을 이용하여 세척한 경우에는 3회 세척시 약 6.7 mg/kg 4, 5회 반복 세척시 각각 약 3.9, 3.3 mg/kg으로 가지역 우려기준에 적합한 농도조건이 됨을 알 수 있었다.

• Korean Journal of Food Science and Technology
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• v.37 no.2
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• pp.312-317
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• 2005

Chemical composition, and mineral and heavy metal contents of Yeomsan and Baekso sun-dried salts (1-5-year-old) were determined. Moisture contents (Yeomsan, 6.07-17.02%; Baekso, 4.29-16.15%) and pH (Yeomsan, 5.92-6.31; Baekso, 5.52-6.23) decreased as age of salts increased, while NaCl contents (Yeomsan, 80.35-92.74%; Baekso, 81.06-94.58%) increased with increasing storage period of salts. Older salts had lower content of water-insoluble matters. Nitrate content was not affected by aging of salts, whereas nitrite content was lower in older salts. Sulfate content of sun-dried salt decreased with aging of salt. Average concentrations (ppm wet weight) of major minerals in Yeomsan and Baekso sun-dried salts were: Mg, Mg, 1002-119; K, 1062-3411; Ca, 1503-3437; Li, 25-101; Ge, 8.35-0.21; Si, 43.99-6.48; and Mn, 6.79-1.55. Mineral content generally decreased with salt aging. Among heavy metals, Hg was not detected in all salts, and Cd (0.02-0.04ppm) was not affected by storage period. Pb was not detected in 5-year-old salts. Older salts showed brighter color than younger ones.

• Clean Technology
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• v.19 no.4
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• pp.487-491
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• 2013

To efficiently desorb gold and copper-cyanide complexes adsorbed onto Dowex21K XLT resin, the mixed solvent with HCl and acetone which is a kind of dipolar aprotic solvent was used as a desorbing agent. The desorption efficiency for gold-cyanide complex was the highest as about 94% when the mixing ratio of HCl and acetone based on volume was the 7:3, however, the value decreased as the ratio of acetone increased. In the case of copper-cyanide complex, most of them was desorbed when the amount of HCl was relatively higher than that of acetone, however, desorption efficiency decreased as the ratio of acetone increased. The desorption efficiency for gold and copper-cyanide complexes was the 94 and 100%, respectively at the 0.6 M of HCl with the 7 (HCl) : 3 (Acetone) of mixing ratio and desorption efficiency for gold-cyanide complex not increased any more even though higher HCl concentration was used. And the desorption efficiency for gold and copper-cyanide complexes was about 100% at the S/L raio ${\leq_-}1.0$ whereas desorption efficiency for gold-cyanide complex was very low as about 20-29% at the S/L ratio > 1.0. Also, most of desorption process for gold and copper-cyanide complexes was completed within 120 min.

• Resources Recycling
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• v.27 no.6
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• pp.53-58
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• 2018

Solvent extraction of Li(I) from weak HCl solution was investigated by the mixture of TBP/MIBK with other neutral extractants such as Cyanex 923, TOPO and TOP. The TBP/MIBK organic phase was loaded with 0.1 M $FeCl_3$ at different HCl concentrations (1-9 M). Extraction of Li(I) from weak HCl solution is related to the stability of $FeCl_3$ in the organic mixture. As HCl concentration increased in preparing the loaded TBP phase, the stripping percentage of Fe(III) during the extraction of Li(I) became reduced and thus Li(I) could be extracted by ion exchange reaction with hydrogen ion in the organic. The concentration of TBP in the extractant mixture affected the stability of $FeCl_3$. Compared to TBP, Fe(III) was easily stripped from the loaded MIBK and thus no Li(I) was extracted by the mixture with MIBK. The nature of neutral extractant with TBP/MIBK showed little difference in the extraction of Li(I) and stripping of Fe(III).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.6
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• pp.785-790
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• 1998

The experimental transportation of Rhynchocypris steindachneri was carried out to study the effects of lidocaine-hydrochloride on water parameters. The dissolved oxygen, ventilation rate, ammonia nitrogen, and pH of control group, sham control group, and lidocaine-hydrochloride treated groups of 2,5 ppm, 5 ppm, 10 ppm and 20 ppm at time of 30 min, 60 min, 90 min, 120 min, 240 min and 360 min after elapsed from treatment were tested. During the experiment time it was found that lidocaine-hydrochloride treated groups were most effective, followed by sham control and control, in decreasing the oxygen consumption and the excretion of ammonia by the fish. There were lidocaine-hydrochloride dose-related decrease in oxygen consumption and the excretion of ammonia. Decreasing in pH value of lidocaine-hydrochloride groups and sham control group was much more higher than that of control group. These results reveal lidocaine-hydrochloride is effective as sedative for transportation mixture in R. steindachneri.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.895-901
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• 1999

The acid characteristics of ${\beta}$-zeolites was modified by the different calcination conditions in order to remove template and the post-treatments such as ammonium ion exchange and HCl treatment. Alkylation of benzene with propene and isopropanol was carried out over the catalysts to investigate the effect of acid characteristics on the selectivity to cumene in this reaction. The $Br{\ddot{o}}nsted$ acidity(IR $3610cm^{-1}$ band) of ${\beta}$-zeolite was significantly reduced by a deep bed calcination compared to that of ${\beta}$-zeolite calcined in a shallow bed. Moreover, extraframework aluminum species which did not show acidity were produced by the framework dealumination on the deep bed calcined ${\beta}$-zeolite. $Br{\ddot{o}}nsted$ acidity of deep bed calcined ${\beta}$-zeolite was significantly recovered by ammonium ion exchange, however, it was partially recovered by a weak HCl treatment. It was found that the framework aluminum as well as the extraframework aluminum were extracted by a strong HCl treatment. The selectivity to cumene was shown to be about 95% on the shallow bed calcined ${\beta}$-zeolite, however, it decreased to 90% on the deep bed calcined one. The post-treatment such as ammonium exchange and weak HCl treatment enhanced the selectivity to cumene up to 93% by the partial recovery of $Br{\ddot{o}}nsted$ acidity. Propene was proved to be a good alkylating agent for the selectivity to cumene compared to isopropanol.

• Resources Recycling
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• v.9 no.3
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• pp.29-36
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• 2000

A study on the recovery of gallium from leaching solutions is carried out by solvent extraction in order to produce gallium oxide of high purity. The results show that the extraction of gallium is found to be increase with acidities of aqueous solution up to 7.4 M/L when pure isopropyl ether is used. And the extraction of iron also increases with increasing acidity of aqueous solution. It appears that the separation of gallium from iron cannot be satisfactorily accomplished with isopropyl ether. But, in the case of extaction with D2EHPA, almost complete extraction of iron is achieved-leaving all the gallium in the aqueous solution-by maintaining the acidity of aqueous solution at 2 M/L. Accordingly, $Ga_2O_3{\cdot}H_2O$ of more than 99wt.% in purity can be produced from zinc residues through the processes comprising of alkali leaching, precipitation by neutralization and solvent extraction using isopropyl ether and D2EHPA as extractants.

• Resources Recycling
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• v.30 no.2
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• pp.24-30
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• 2021

Dismantling tests were performed to separate components from waste printed circuit boards (PCBs) using HCl solution with Sn4+. Then, the effects of agitation speed, reaction temperature, initial Sn4+ concentration, and HCl concentration on the dismantling of components were investigated. No significant effect on the dismantling speed was observed upon changing the agitation speed from 100 to 300 rpm. However, the dismantling rate increased with increasing reaction temperature, Sn4+ concentration, and HCl concentration. In the all-component dismantling tests, when the dismantling ratio increased to 100%, no solder was observed on the boards, and the Sn4+ concentration was ~1,500 mg/L. The dismantling ratio of the components from the PCB increased to 100% within 2 h when 1 mol/L HCl solution with 10,000 mg/L Sn4+ was used at an agitation speed and temperature of 200 rpm and 90 ℃, respectively.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.58-64
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• 2005

Several tests were conducted to determine the optimum operational conditions of soil washing techniques for floe-forming arsenic-contaminated soils, collected from D abandoned Iron-mine in Korea. The optimum cut-off size was 0.15 mm $(sieve\;\#100)$, about $94\%$ of the mass of soils. Both sodium hydroxide and hydrochloric acid were effective to remove arsenic and the optimum mixing ratio (soil [g] : washing solution [mL]) was 1:5 for both washing agents. Arsenic concentrations, determined by KST Methods, for the dried floe solids obtained from flocculation at pH 5-6 were $990\~1,086\;mg/kg$ dry solids, which were higher concentrations than at the other pH values. Therefore, batch tests for sequential washings with or without removing floc were conducted to find the enhancement of washing efficiencies. After removing floe with 0.2 M HCl, sequential washings of 1 M HCl followed by 1 M NaOH showed the best results (15 mg/kg dry soil). The arsenic concentrations of washing effluent from each washing step were about $2\~3\;mg/L$. However, when these acidic and basic effluents were mixed together, arsenic concentration was decreased to be less than $50\;{\mu}g/L$, due to the pH condition of coagulation followed by precipitation for arsenic removal.

• Resources Recycling
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• v.20 no.1
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• pp.61-68
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• 2011

Impurity removal from metallurgical grade silicon by acid washing at $50^{\circ}C$ was investigated by employing sulfuric, nitric acid and the mixture of hydrochloric and hydrofluoric acid. Acid washing treatment had no effect on the removal of boron and the concentration of this clement after treatment was rather increased. In our experimental range, the removal percentage of phosphorus was 60%. In the acid washing with sulfuric and nitric acid, the removal percentage of major impurities was below 50%, which indicates that refining effect was not great with these acids. Acid washing with the mixture of hydrochloric and hydrofluoric acid led to removal percentage of higher than 90%. Data on the purity of silicon after acid washing at various conditions are reported.