• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.460-465
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• 2004

Hydrofluoric acid has been used as a novel stripping agent for molybdenum(VI) after its extraction with Cyanex 301. In the extraction step, the effects of parameters such as type and initial concentration of acid, type of diluent, extractant concentration, metal concentration and temperature have been studied. In the stripping step, the effects of various stripping agents on stripping efficiency have been investigated. Hydrofluoric acid has been chosen as an effective stripping agent, and the effects of concentration of hydrofluoric acid, stripping time, volume of hydrofluoric acid and the number of stages of stripping have been studied. Molybdenum(VI) has been effectively separated from a large number of elements in binary mixtures, with a very high tolerance limit. Finally, the optimized method has been extended for the analysis of Mo(VI) in spent molybdenum catalysts.

• YAKHAK HOEJI
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• v.42 no.3
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• pp.243-247
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• 1998

A method for the determination of basic drugs based on their reaction with picric acid to form an ion-association complex extractable into several plasticizers was developed. Ba sic drugs-picric acid complexes in acid medium could be extracted quantitatively into several plasticizers except phosphates. For example, the chlorpromazine-picric acid complex showed maximum absorbance at near 410nm and was applied to extraction spectrophotometric determination of chlorpromazine. The calibration curves are linear (r>0.998) within a range from $10^{-6}to\;5{\times}10^{-4}M$ and the precision of the method was acceptable because RSD was less than 2.6% (n=7). The factors affecting the extraction system was discussed.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.157-161
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• 1982

The possibility of extraction of alumina from domestic Ha-dong kaolin was studied by sulfuric acid treatment. Raw kaolin was calcined at various temperature (500-110$0^{\circ}C$) and calcined kaolin were treated with sulfuric acid. The tendency of extraction yield of alpha alumina have been investigated by relating reaction time, temperature, and acid concentration. After reaction, precipitates were analyzed by DTA, TGA, and identified alpha alumina by X-ray diffractometer with calcined sample at 120$0^{\circ}C$. The results were as follows; 1. The optimum calcination temperature was 800-86$0^{\circ}C$. 2. The most suitable extracting conditions of alpha alumina were 40 wt%-$H_2SO_4$, 2-3 hours acid-treating time and 8$0^{\circ}C$ acid-treating temperature. 3. Precipitates were composed of $(NH_4)_2SO_4$, $Al_2SO_4(OH)_4$ 5-7 $H_2O$ and $Al(OH)_3$.

• Journal of the Korean Chemical Society
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• v.12 no.4
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• pp.155-159
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• 1968

On the extraction of humic acid from peat, the optimum conditions were studied and the effects of them on the characteristics of humic acid were also examined by means of infrared spectroscopy. 1. Pretreatment of peat with diluted 6-8% HCl solution for 5 hrs. prior to extraction with alcohol-benzol azeotropic mixture have resulted the better yield of humic acid. The water soluble Na-humates were obtained by the subsequent extraction with one hundred times quantity of caustic soda solutieon for 1hr. at 90 $^{\circ}C$. Thus the pure humic acids have been yielded approximately 40% (by wt.) from the raw peat. 2. In characteristics of humic acid, the chemical structure, mainly the contents of such functional groups as -COOH, -OH (phenol type), $-CH_2CO-$, $-CH_2{\cdot}O{\cdot}CH_2-$ and aromatic rings were varied according to the concentration of alkaline solution, temperature and time when the humic acids were extracted with alkali.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.478-481
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• 2001

The spent petrochemical catalyst used in the manufacturing process of terephthalic-acid contains valuable metals such as cobalt and manganese. To recover these metals, sulfuric acid leaching was performed with hydrogen peroxide as a reducing agent. Low extractions of Mn, Co and Fe were obtained by sulfuric acid leaching without reducing agent. With adding hydrogen peroxide as a reducing agent, the high extraction of these metals could be obtained. Different from general leaching experiment, the extraction rates of metal components were decreased with increasing reaction temperature in this case. Under the optimum condition, the extraction rates of Mn, Co and Fe were 93.0%, 87.0% and 100% respectively.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.687-693
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• 2018

The selective removal and recovery of fermentation inhibitors during purification of sugars from biomass hydrolysates can increase the economic efficiency of the entire process to produce bioalcohol from lignocellulosic biomass. This study investigated the effect of furans in phenols-free biomass hydrolysate on acetic acid extraction in an emulsion liquid membrane system. Under specific operating conditions, more than 99% of acetic acid could be extracted within 5 minutes, and the degrees of extraction of furfural and 5-hydroxymethylfurfural were about 10% and 4%, respectively. The extraction rate of acetic acid was also lower at a higher initial concentration of furfural in the feed phase, which was greater for furfural than 5-hydroxymethylfurfural. Thus, if furfural is first removed from the hydrolysate prior to acetic acid extraction, emulsion liquid membrane would be a more economically efficient way of removing acetic acid.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.115-121
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• 2012

This study was performed to assess the possibility of application of sewage sludge which is the side-product from domestic sewage treatment plant to the materials for biodiesels by investigating the yields and composition of the lipids and fatty acid methyl esters(FAMEs) from soxhlet extraction and in-situ transesterification. As the results, yields of in-situ transesterification were higher than soxhlet extraction. In comparison by sewage sludge type, yields of sewage sludge mixed nightsoil or livestock were higher than a single sewage sludge. And maximum yield showed up to 14 wt%. Fatty acid composition of extracted lipids and synthesized FAMEs consists of palmitic acid(C16:0), palmitoleic acid(C16:1), stearic acid(C18:0), oleic acid(C18:1), and linoleic acid(C18:2).

• Resources Recycling
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• v.7 no.5
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• pp.46-51
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• 1998

A study has been on the recovery of nitric acid and valuable metals such as Fe, Cu, Sn, Pb, from spent nitric etching solutions. The effects of extractant of extractant type, concentrations, phase raios and selectivity from Fe, Cu, Sn, Pb on nitric acid extraction were studied. The results showed that TBP as an extractant for recovering of nitric acid was more effective than Alamine336, and the optimal concentration of TBP was found to be 60~70% of organic phase. Also, the nitric acid were only extracted by TBP from the spent etching solutions and the heavy metals such as Fe, Cu, Sn, Pb were not extracted above 0.1N nitric acid in spent etching solutions, From the analysis of McCabe-Thiele diagram, the extraction of 95% nitric acid is attained at a ratio of O/A=3 with five stages by 60% TBP and the stripping of 98% nitric acid from 80 g/l nitric acid in organic phase is attained at a ratio of O/A=1 with four stages by distilled water.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.298-301
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• 2000

Heavy metals are extracted from stream sediments, roadside soils and sediments and soils and tailings from mining area using partial extraction, acid digestion and HF-digestion. Compared to amounts of heavy metals extracted using partial extraction, those extracted using acid digestion are higher by 2.0∼220.9 times in Cu, 2.4∼2806.1 times in Pb, 1.3∼121 times in Cd, 14.1∼1300885 times in Fe, 1.2∼271.5 times in Mn, 1.3∼372.5 times in Zn, 2.2∼1734.5 times in Cr. Although partial extraction, which extracts less amounts of heavy metals from soil compared to acid digestion, is used in domestic standard method for examination of soil, domestic soil standard for heavy metals in non-agricultural and industrial areas is higher than soil standard in foreign countries which use acid digestion, For improvement of the domestic standard method for assessment of soil, it is suggested to lower the domestic soil standard for heavy metals or to change pretreatment method for extracting heavy metals from partial extraction to acid digestion with modifying the soil standard.

• Food Science of Animal Resources
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• v.39 no.3
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• pp.446-458
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• 2019

The aim of this study was to investigate the oxidative status and quality characteristics of four animal skin-derived fats extracted using an identical extraction method. Pressurized hot water extraction, a green extraction method, was used to extract animal skin fats (duck, chicken, swine, and bovine skin). Multiple experiments were performed during accelerated storage at $60^{\circ}C$ for 90 days. Quality characteristics, such as extraction yield, iodine value (IV), fatty acid composition, and fat viscosity were determined. In addition, indicators for oxidative status, including acid value (AV), peroxide value (PV), p-anisidine value (p-AV), thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD), and total oxidation (totox) values were evaluated. The fat extraction yield was highest in bovine fat, followed by duck, swine, and chicken fats. The IV was higher in duck and chicken fats. Duck fats contained the most unsaturated fats and the least saturated fats. Fat oxidation indicators, such as PV, TBARS, and totox values, were relatively higher in duck fats during storage compared to the other fats. Other indicators, including AV, p-AV, and CD, were similar in duck, chicken, and swine fats. Viscosity was similar in all the tested fats but markedly increased after 70 days of storage in duck fats. Our data indicate that duck skin fat was more vulnerable to oxidative changes in accelerated storage conditions and this may be due to its higher unsaturated fatty acid content. Supplementation with antioxidants might be a reasonable way to solve the oxidation issue in duck skin fats.