• Title, Summary, Keyword: selective removal

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A study on removal of 1,4-dioxane in drinking water by multi filtration system (다단계 필터시스템에서의 음용수 중 1,4-Dioxane 제거)

  • Lee, Kang Jin;Pyo, Heesoo;Yoo, Je Kang;Lee, Dae Woon
    • Analytical Science and Technology
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    • v.18 no.2
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    • pp.154-162
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    • 2005
  • Recently, 1,4-Dioxane is known as the contaminant in water plants in Korea. Owing to its toxicity and potential health effect, 1,4-Dioxane must be determined at very low levels in drinking water. Studies on the removal of 1,4-Dioxane in drinking water were performed by using multi filtration system with activated carbons and membrane filter. For extraction of 1,4-Dioxane, methyl-t-butyl ether (MTBE) was used and then analyzed using gas chromatography-mass selective detection (GC/MSD). Removal experiment was proceeded for 300 L with a sample volume of 30 L. At first. The removal was 70%, 95% and 100% after using activated carbon, membrane and second activated carbon respectively. At larger accumulated water fluxes, the removal rate decreased at each filter. After the flow volume was 300 L, the removal rate was 30%, 88% and 99% through the first activated carbon, membrane and second activated carbon respectively.

Comparative Analysis of Two Selective Bleaching Methods on Alpaca Fibers

  • Liu, Xin;Hurren, Christopher J.;Wang, Xungai
    • Fibers and Polymers
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    • v.4 no.3
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    • pp.124-128
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    • 2003
  • Dark brown Alpaca fiber was reduced in shade via selective bleaching with peroxide. Two selective oxidative bleaching methods were tested on alpaca top to assess their effectiveness for color removal and fiber quality properties. Color change, bundle strength, weight loss, fiber diameter, surface modification, dye-ability and dye wash fastness were assessed for both methods and compared with the original brown top. Bleach method 1 (BL-I) showed little surface modification, 5.8% weight loss and 2.4% strength loss. D1925 yellowness index was reduced to 74.3 from 83.1 and provided a good base for the dyeing of medium to deep shades. Bleach method 2 (BL-II) displayed considerable surface modification, 7.8% weight loss and 18% strength loss. BL-II also resulted in a mean diameter reduction of 1.9 micron during bleaching. Yellowness was reduced to 64.5 from 83.1 and provided a very good base for the dyeing of medium to deep shades. BL-I showed better exhaustion of the premetallised dye Lanaset Violet B than BL-II. Wash fastness for BL-II was 1 grey scale unit poorer than BL-I. BL-II showed far better color clarity at pale depths however the wash fastness of the finished product was not good enough to maintain the depth or clarity of the color. BL-I showed poorer clarity of color but exhibited better wash fastness results.

Agglomeration of fine anthracite using oil and modified styrene (Oil과 Modified Styrene을 사용(使用)한 미립(微粒) 무연탄(無煙炭)의 응집(凝集))

  • Lee, Jae-Jang;Jang, Dong-Sung
    • Journal of Industrial Technology
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    • v.7
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    • pp.27-47
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    • 1987
  • Fine anthracite is very difficult to upgrade by conventional processes such as gravity concentration or froth flotation, because large quantities of fine coals are generated at the mining and preparation stages and a significant portion of these fine coals are mixed with gangue minerals. This study, therefore, was carried out for the purpose of improving recovery of low ash clean coal, effective beneficiation of low-grade coking coal and removal of sulphur from high-sulphur coals by employing the method of selective agglomeration using oil or polystrene flocculants, for coals which are generally hydrophobic in nature will be extracted by using flocculants. Studies were performed by varying solid concentration, concetration of bridging liquid, mixing speed and mixing time, balling speed and balling time, dispersant dosage, flocculant dosage, pulp pH, and particle size. The results were : when the methods of the oil agglomeration and selective flocculation were employ(in the two process the sample was ground to the size of -74 micron), 1) ash content of the agglomerated coal was 9.85, 7.83%, 2) combustibel recovery of it was 98.5%, 93.5%, respectively. It was observed in selective flocculation that polystyrene is an effective flocculant for coal, De-entrapment of shale from the concentrate flocculated by mechanical agitation was necessary for substantional reductions in final ash content.

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Selective Chlorination of Iron from Titaniferrous Magnetite in a Fluidized Bed Reactor (유동층 반응기에서 함티탄자철광의 선택염소화 반응)

  • Lee, Sang-Soon;Lee, Chul-Tae
    • Applied Chemistry for Engineering
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    • v.3 no.3
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    • pp.451-463
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    • 1992
  • A selective chlorination of titaniferrous magnetite in a fluidized bed reactor was investigated to find the optimum condition for selective removal of Fe component from low grade titaniferrours magnetite ore and to produce a rutile substitute from titaniferrous magnetite ore. The optimum chlorination condition was determined to be a temperaure of $950^{\circ}C$, 2hr of reaction time, reducting agent(petroleum coke) to titaniferrous magnetite weight ratio of 0.12, and $Cl_2$ gas velocity of 5cm/sec. Under the above mentioned condition, 99% of Fe in titaniferrous magnetite was removed and the reaction residue which became rutile substitute was identified as rutile by x-ray diffraction and was found to contain 70% $TiO_2$.

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Experimental Study on the Velocity Structure of 2-D Density Current Induced by Selective Withdrawal (선택취수에 의한 2차원 밀도류의 흐름특성에 관한 실험적 연구)

  • Lyu, Siwan;Kim, Young Do;Cho, Gilje;Kwon, Jae Hyun;Lee, Nam Joo
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.6
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    • pp.825-832
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    • 2009
  • A series of laboratory experiments has been performed to investigate the flow characteristics of 2-dimensional density currents induced by selective withdrawal, which is commonly suggested as a measure for removal of high turbid water from reservoirs. Saltwater has been used to simulate the density stratification over depth and PIV(Particel Image Velocimetry) for observing the velocity structure. Experimental conditions have been established according to Richardson number, which is the dimensionless number that expresses the ratio of potential to kinetic energy. From the experiments, the patterns of longitudinal decay of centerline axial velocity induced by the withdrawal have been distinguished from other experimental cases. The rate of longitudinal decay increase as the Richardson number increases. The variations of volumetric and momentum flux along the longitudinal axis have also shown to be dependent on Richardson number.

Low Temperature Selective Catalytic Reduction of NOx over V2O5/TiO2 Catalyst Doped with Mn (Mn이 첨가된 V2O5/TiO2 촉매상에서 질소산화물의 저온 SCR 특성)

  • Cheon, Tae Jin;Choe, Sang Gi;Choe, Seong U
    • Journal of Environmental Science International
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    • v.13 no.6
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    • pp.537-542
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    • 2004
  • $V_{2}O_{5}/TiO_{2}$ catalysts promoted with Mn were prepared and tested for selective catalytic reduction of NOx in $NH_3.$ The effects of promoter content, degree of catalyst loading were investigated for NOx activity while changing temperatures, mole ratio, space velocity and $O_2$ concentration. Among the various $V-{2}O_{5}$ catalysts having different metal loadings, $V-{2}O_{5}$(1 wt.%) catalyst showed the highest activity(98%) under wide temperature range of $200-250^{\circ}C.$ When the $V-{2}O_{5}$ catalyst was further modified with 5 wt.% Mn as a promoter, the highest activity(90-47%) was obtained over the low temperature windows of $100-200^{\circ}C.$ From Mn-$V_{2}O_{5}/TiO_{2}$, it was found that by addition of 5 wt.% Mn on $V_{2}O_{5}/TiO_{2}$ catalyst, reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and NOx reduction. According to the results, NOx removal decreased for 10%, but the reaction temperature down to $100^{\circ}C.$

A Finite Element Model of Melt Pool for the Evaluation of Selective Laser Melting Process Parameters (선택적 레이저 용융 공정의 공정변수 평가를 위한 용융풀 유한요소 모델)

  • Lee, Kanghyun;Yun, Gun Jin
    • Journal of the Korea Institute of Military Science and Technology
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    • v.23 no.3
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    • pp.195-203
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    • 2020
  • Selective laser melting(SLM) is one of the powder bed fusion(PBF) processes, which enables quicker production of nearly fully dense metal parts with a complex geometry at a moderate cost. However, the process still lacks knowledge and the experimental evaluation of possible process parameter sets is costly. Thus, this study presents a finite element analysis model of the SLM process to predict the melt pool characteristics. The physical phenomena including the phase transformation and the degree of consolidation are considered in the model with the effective method to model the volume shrinkage and the evaporated material removal. The proposed model is used to predict the melt pool dimensions and validated with the experimental results from single track scanning process of Ti-6Al-4V. The analysis result agrees with the measured data with a reasonable accuracy and the result is then used to evaluated each of the process parameter set.

Removal of NOx by Selective Catalytic Reduction Using Ceramic Foam Supports (SCR반응에서 세라믹 폼 지지제를 이용한 NOx 제거)

  • 한요섭;김현중;박재구
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • pp.141-142
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    • 2003
  • 최근 자동차 수요증가 및 산업용 보일러 둥 급증하는 추세이며 이로 인한 대도시 대기오염 문제는 위험수위에 도달해 있다. 이러한 산업용 보일러, 화력발전소등 고정배출원과 자동차에서 발생하는 배기가스에는 인체에 유해한 일산화탄소(CO), 질소산화물(NOx), 황산화물(SOx)등이 다량 함유되어 있다. 유독성 가스중 질소산화물(NOx) 저감방법에는 특히 선택적 촉매환원법(Selective Catalytic Reduction, SCR)이 가장 널리 적용되고 있다. SCR법은 촉매하에서 NH$_3$, CO, 탄화수소(메탄, 에탄올, 프로판 등)의 환원제를 사용하여 NOx를 $N_2$로 전환하시키는 기술이다. (중략)

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Removal of Nitrate-Nitrogen in Pickling Acid Wastewater from Stainless Steel Industry Using Electrodialysis and Ion Exchange Resin (전기투석과 이온교환수지를 이용한 스테인레스 산업의 산세폐수 내 질산성 질소의 제거)

  • Yun, Young-Ki;Park, Yeon-Jin;Oh, Sang-Hwa;Shin, Won-Sik;Choi, Sang-June;Ryu, Seung-Ki
    • Journal of Environmental Science International
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    • v.18 no.6
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    • pp.645-654
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    • 2009
  • Lab-scale Electrodialysis(ED) system with different membranes combined with before or after pyroma process were carried out to remove nitrate from two pickling acid wastewater containing high concentrations of $NO_3\;^-$(${\approx}$150,000 mg/L) and F($({\approx}$ 160,000 mg/L) and some heavy metals(Fe, Ti, and Cr). The ED system before Pyroma process(Sample A) was not successful in $NO_3\;^-$ removal due to cation membrane fouling by the heavy metals, whereas, in the ED system after Pyroma process(Sample B), about 98% of nitrate was removed because of relatively low $NO_3\;^-$ concentration (about 30,000 mg/L) and no heavy metals. Mono-selective membranes(CIMS/ACS) in ED system have no selectivity for nitrate compared to divalent-selective membranes(CMX/AMX). The operation time for nitrate removal time decreased with increasing the applied voltage from 10V to 15V with no difference in the nitrate removal rate between both voltages. Nitrate adsorption of a strong-base anion exchange resin of $Cl\;^-$ type was also conducted. The Freundlich model($R^2$ > 0.996) was fitted better than Langmuir mode($R^2$ > 0.984) to the adsorption data. The maximum adsorption capacity ($Q^0$) was 492 mg/g for Sample A and 111 mg/g for Sample B due to the difference in initial nitrate concentrations between the two wastewater samples. In the regeneration of ion exchange resins, the nitrate removal rate in the pickling acid wastewater decreased as the adsorption step was repeated because certain amount of adsorbed $NO_3\;^-$ remained in the resins in spite of several desorption steps for regeneration. In conclusion, the optimum system configuration to treat pickling acid wastewater from stainless-steel industry is the multi-processes of the Pyroma-Electrodialysis-Ion exchange.

Electrosorption of Uranium Ions in Liquid Waste

  • Lee, Hye-Young;Jung, Chong-Hun;Oh, Won-Zin;Park, Jin-Ho;Shul, Yong-Gun
    • Carbon letters
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    • v.4 no.2
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    • pp.64-68
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    • 2003
  • A study on the electrosorption of uranium ions onto a porous activated carbon fiber (ACF) was performed to treat uraniumcontaining lagoon sludge. The result of the continuous flow-through cell electrosorption experiments showed that the applied negative potential increased the adsorption kinetics and capacity in comparison to the open-circuit potential (OCP) adsorption for uranium ions. Effective U(VI) removal is accomplished when a negative potential is applied to the activated carbon fiber (ACF) electrode. For a feed concentration of 100 mg/L, the concentration of U(VI) in the cell effluent is reduced to less than 1 mg/L. The selective removal of uranium ions from electrolyte was possible by the electrosorption process.

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