• Title, Summary, Keyword: subcritical water

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Extraction of PCBs by Subcritical Water Extraction (Subcritical Water Extraction에 의한 PCBs 추출)

  • Kwak, Dong Hwan;Moon, Ji Yong;Lee, Sung In;Jeong, Gi Ho
    • Analytical Science and Technology
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    • v.13 no.4
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    • pp.511-519
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    • 2000
  • Water in the supercritical state ($T{\geq}374^{\circ}C$, $p{\geq}221$ atm) is a good solvent for nonorganic pollutants, but it is extremely corrosive. Subcritical Water Extraction (SWE) is a very fast and an efficient method to extract nonpolar environmental pollutants adsorbed on the sediments and soils. Many nonpolar organic compounds are sufficiently soluble to be extracted to the water under subcritical conditions. Complete extraction of PCBs from the sediments and soils takes only a few minutes by applying SWE with the subcritical water at 50 atm and at $260^{\circ}C$.

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In vitro cytotoxic activity of ginseng leaf/stem extracts obtained by subcritical water extraction

  • Lee, Kyoung Ah;Kim, Kee-Tae;Chang, Pahn-Shik;Paik, Hyun-Dong
    • Journal of Ginseng Research
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    • v.38 no.4
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    • pp.289-292
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    • 2014
  • Ginseng leaf/stem extract produced by subcritical water extraction at high temperature ($190^{\circ}C$) posses higher cytotoxic activity against human cancer cell lines than ethanol extract. Subcritical water extraction can be a great candidate for extraction of functional substance from ginseng leaves/stems.

Extraction of Reducing Sugar with Anti-Oxidative Scavengers from Peels of Carya cathayensis Sarg.: Use of Subcritical Water

  • Shimanouchi, Toshinori;Ueno, Shohei;Yang, Wei;Kimura, Yukitaka
    • Environmental Engineering Research
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    • v.19 no.1
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    • pp.41-45
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    • 2014
  • The peels of Carya cathayensis Sarg. (PCCS) were treated under subcritical water conditions ($130^{\circ}C$ to $280^{\circ}C$ for 0 to 120 min). The extract from PCCS included reducing sugar, proteins, and compounds with radical scavenging activity. Addressing the reducing sugar that is a resource of bioethanol, we could maximize the reducing sugar under the subcritical water ($190^{\circ}C$ for 60 min) and obtain 0.24 g/g-sample together with 9.7 units/mg-sample of radical scavenging activity. The obtained extract was estimated to correspond to 1 L of bioethanol/100 g-sample. It was therefore considered that the treatment by subcritical water could yield reducing sugar and natural compounds with radical scavenging activity.

Effects of Soy Protein Hydrolysates Prepared by Varying Subcritical Media on the Physicochemical Properties of Pork Patties

  • Lee, Yun-Kyung;Ko, Bo-Bae;Davaatseren, Munkhtugs;Hong, Geun-Pyo
    • Food Science of Animal Resources
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    • v.36 no.1
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    • pp.8-13
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    • 2016
  • This study investigated the effect of soy protein hydrolysates (SPH) prepared by varying subcritical media on the physicochemical properties of pork patties. For resource of SPH, two different soybean species (Glycine max Merr.) of Daewonkong (DWK) and Saedanbaek (SDB) were selected. SPH was prepared by subcritical processing at 190℃ and 25 MPa under three different of media (water, 20% ethanol and 50% ethanol). Solubility and free amino group content revealed that water was better to yield larger amount of SPH than ethanol/water mixtures, regardless of species. Molecular weight (Mw) distribution of SPH was also similar between two species, while slightly different Mw distribution was obtained by subcritical media. For pork patty application, 50% ethanol treatment showed clear red color comparing to control after 14 d of storage. In addition, ethanol treatment had better oxidative stability than control and water treatment based on thiobarbituric acid-reactive substances (TBARS) analysis. For eating quality, although 20% ethanol treatment in SDB showed slightly higher cooking loss than control, generally addition of SPH did not affect the water-binding properties and hardness of pork patties. Consequently, the present study indicated that 50% ethanol was the best subcritical media to produce SPH possessing antioxidant activity, and the SPH produced from DWK exhibited better antioxidant activity than that produced SDB.

Study on Subcritical Water Degradation of RDX Contaminated Soil in Batch and Dynamic Mode (배치형과 연속흐름형에 의한 토양 중 RDX의 아임계 분해특성 비교연구)

  • Choi, Jae-Heon;Lee, Hwan;Lee, Cheol-Hyo;Kim, Ju-Yup;Park, Jeong-Hun;Jo, Young-Tae
    • Journal of Soil and Groundwater Environment
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    • v.20 no.6
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    • pp.95-102
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    • 2015
  • The purpose of this study is to compare the degradation characteristics by subcritical water of RDX contaminated soil using batch mode and dynamic mode devices. First, upon application of RDX contaminated soil, RDX treatment efficiency was increased with increasing the temperature in both modes. At 150℃, the treatment efficiency was 99.9%. RDX degradation efficiency got higher with lower ratio of solid to liquid. However, the treatment efficiency in the dynamic mode tended to be decreased at a certain ratio of solid to liquid or lower. The treatment efficiency was increased when it took longer time for the reactions in both modes. As the results of analysis on concentration of treated water after subcritical water degradation, the RDX recovery rate of dynamic and batch modes at 150℃ was 10.5% and 1.5%, respectively. However, both modes showed very similar recovery rates at 175℃ or higher. RDX degradation products were analyzed in treated water after it was treated with subcritical water. According to the results, RDX degradation mechanism was mostly oxidation reaction and reduction reaction was partially involved. Therefore, it suggested that most of RDX in soil was degraded by oxidation of subcritical water upon extraction. According to this result, it was found that both batch and dynamic modes were very effectively applied in the treatment of explosive contaminated soil.

On Application of Computation Method of Water Surface Profile Using HEC-2 (수면곡선계산법의 적용에 대한 연구 -HEC-2모형 이용을 중심으로-)

  • 이정규;이창해
    • Water for future
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    • v.26 no.3
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    • pp.103-111
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    • 1993
  • The HEC(Hydrologic Engineering Center)-2 program, which utilize the standard step method, is usually adopted in the practical works for the water surface profile computation of natural channels. Water profile computation is, in general, carried upstream for subcritical flow. On the other hand, when the reference water surface si given upstream, numerous efforts and a great deal of time are necessary to compute the downstream water surface profile for subcritical flow. A simple method, computing the water surface profile from upstream to downstream for subcritical flow by HEC-2, is suggested in this paper. The applicability and the accuracy of this method are discussed by applying this method to both prismatic and natural channels.

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Remediation of Soil Contaminated with Persistent Organic Pollutants through Subcritical Water Degradation (아임계수 분해를 이용한 난분해성 물질로 오염된 토양의 정화 연구)

  • Choi, Jae-Heon;Lee, Hwan;Lee, Cheol-Hyo;Kim, Ju-Yup;Oh, Seok-Young
    • Journal of Korean Society of Environmental Engineers
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    • v.37 no.2
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    • pp.113-119
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    • 2015
  • This study examined remediation of soil contaminated with polychlorinated biphenyls (PCBs) and other persistent organic pollutants by using subcritical water. Our results showed that removal efficiency of PCBs from soil and treatment temperature were linearly proportional under subcritical conditions. The removal efficiency as increased as reacting period increased. PCBs contaminating fine particles in soil were less effectively removed than those in entire contaminated soil. Reaction of the zero-valent iron and PCBs under subcritical condition produced dechlorinated product, where most of the PCBs were oxidised while little remained as dechlorinated. Other organic pollutants, such as TPH, BTEX, TCE/PCE, and chlorpyrifos, were removed by more than 90% at $300^{\circ}C$. Considering removal efficiency and identification of by-products, we suggest that subcritical water treatment may be effectively applied to soils contaminated with various persistent organic pollutants.

Effects of Ethanol Addition on the Efficiency of Subcritical Water Extraction of Proteins and Amino Acids from Porcine Placenta

  • Park, Sung Hee;Kim, Jae-Hyeong;Min, Sang-Gi;Jo, Yeon-Ji;Chun, Ji-Yeon
    • Food Science of Animal Resources
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    • v.35 no.2
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    • pp.265-271
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    • 2015
  • In a previous study, hydrolysates of porcine placenta were obtained and the extraction efficiency for proteins and amino acids was compared between sub- and super-critical water extraction systems; optimum efficiency was found to be achieved using subcritical water ($170^{\circ}C$, 10 bar). In this study, the effects of adding ethanol to the subcritical water system were investigated. The lowest-molecular-weight extraction product detected weighed 434 Da, and the efficiency of extraction for low-molecular-weight products was increased when either the concentration of ethanol was decreased, or the extraction time was lengthened from 10 min to 30 min. The highest concentration of free amino acids (approximately 8 mM) was observed following 30 min extraction using pure distilled water. The concentration of free amino acids was significantly lower when ethanol was added or a shorter extraction time was used (p<0.05). Color change of the solution following extraction was measured. There were no significant differences in color between lysates produced with different extraction times when using distilled water (p>0.05); however, using different extraction times produced significant differences in color when using 20% or 50% ethanol solution for subcritical extraction (p<0.05). The range of pH for the hydrolysate solutions was 6.4-7.5. In conclusion, the investigated extraction system was successful in the extraction of $\leq$ 500 Da hydrolysates from porcine placenta, but addition of ethanol did not yield higher production of low-molecular-weight hydrolysates than that achieved by DW alone.

Efficient Flavonoid Extraction from Apple Peel by Subcritical Water and Estimation of Antioxidant Activity (아임계수를 이용한 사과 과피 플라보노이드의 효율적 추출 및 항산화 활성 평가)

  • Cheigh, Chan-Ick;Yoo, Seo-Yeon;Chung, Myong-Soo
    • The Korean Journal of Food And Nutrition
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    • v.24 no.3
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    • pp.458-463
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    • 2011
  • The effect of subcritical water for the extraction of total polyphenols and flavonoids from apple peel was investigated, and then the antioxidant activity of the extracts was estimated. Maximum yields of total polyphenolic compounds($36.4{\pm}1.9mg$ quercetin equivalent(QE)/g dried material) and flavonoids($9.9{\pm}0.8mg$ QE/g dried material) were obtained by subcritical water extraction(SWE) with operating conditions of $190^{\circ}C$, 1,300 psi, and 20 min. Furthermore, the highest antioxidant activity($76.1{\pm}1.1%$) was observed in the extract obtained from SWE using the same conditions. The flavonoids from the SWE of apple peel were compared to three conventional extraction methods in terms of their extraction efficiency and antioxidant activity. The SWE was significantly more effective than hot water ($90^{\circ}C$), methanol, and ethanol extraction for flavonoid yield by 4.7-, 2.2-, and 1.3-fold, respectively, and for antioxidant activity by 11.0-, 4.9, and 2.8-fold, respectively.