1,721,183 research outputs found
Local convective mass transfer on circular cylinder with transverse annular fins in crossflow
No full textAn experimental study was made of local mass transfer from a circular cylinder, which is situated between two annular fins in a crossflow. Low turbulence-intensity wind tunnel experiments were conducted over moderate Reynolds numbers, 33 000 < Re-d < 80 000. Velocity measurements were analyzed to examine the characteristics of the boundary layer, which is developed on the flat annular fin. The naphthalene sublimation technique was employed to measure the local convective mass transfer around the circular cylinder. The ratio of the axial gap distance between two axial fins (L) to the radial protrusion length of the annular fin (H) was an important experimental parameter, and its range was 0 < L/H < 0.40. The impact of horseshoe vortices on local mass transfer was scrutinized. For a small gap distance (L/H = 0.05), naphthalene sublimation is intense in the front portion of the cylinder, especially near the separation region. When the gap distance is moderate (L/H = 0.15), the overall character of sublimation shows a more organized pattern. The influence of horseshoe vortices is substantial. For a large gap distance (L/H = 0.40), a dominant role of horseshoe vortices near the corner junction is discernible
Immobilization behavior of methyl tert-butyl ether by cyclodextrins
No full textThe immobilization behavior of methyl tert-butyl ether (MTBE) by various cyclodextrins (CDs) was studied. Although it has a low hydrophobic character and high polarity compared to other organics, MTBE was effectively immobilized by CDs. The immobilization isotherm was a type of Freundlich isotherm. The immobilization capacity of beta-CDs was the largest of the natural CDs. The initial apparent association constant for MTBE-CD complex follows the order: gamma = beta > methyl-beta > hydroxypropyl beta > alpha. The difference in these constants is related to the size of MTBE and CDs. The size of beta- and gamma-CD is large enough to encapsulate MTBE molecule into the cavity, which that of alpha-CD is too small to encapsulate MTBE. (C) 2003 Elsevier B.V. All rights reserved
Removal of perchlorate from groundwater by the polyelectolyte-enhanced ultrafiltration process
No full textThe polyelectrolyte enhanced ultrafiltration (PEUF) process for perchlorate removal from groundwater containing common co-contaminants like nitrate and sulfate was investigated. Existing processes such as ion exchange can remove perchlorate but with greater complexity, especially when applied in the presence of high nitrate and sulfate concentration. The effect of cationic polyelectrolyte, poly(diallyldimethyl ammonium chloride) (PDADMAC) concentration and the effect of nitrate and sulfate in a broader concentration range were observed. In the absence of other anions, a lower amount of PDADMAC (0.5-1 mM) can remove more than 90% of perchlorate from the aqueous phase. However, in the presence of 5 mM nitrate, perchlorate removal decreases as the available binding sites of PDADMAC for perchlorate are reduced. In the presence of both 1 mM to 10 mM nitrate and sulfate, 60-80% perchlorate was removed with 30 mM PDADMAC. The removal of sulfate and nitrate in this case was nearly 75% and 65%, respectively. The effect of other parameters such as relative flux, membrane material and pore size were also observed to study the feasibility of PEUF for perchlorate removal. Consequently, PEUF proved to be an effective perchlorate removal process owing to the high removal efficiency and suitability in groundwater remediation containing other contaminants
Application of MEUF on removal heavy metal in the wastewater containing chelating agent by using a cationic surfactant
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Removal of perchlorate from groundwater by polyelectrolyte enhanced ultrafiltration process
No full textEffect of nitrate & Sulfate in perchlorate removal from groundwater by surfactant mediated preciptation method
No full textCationic starch-enhanced ultrafiltration for Cr(VI) removal
No full textThe feasibility of cationic starch-enhanced ultrafiltration (CSEUF) was investigated to remove chromate from the aqueous stream. Cationic starch is a modified starch with cationic functional groups, which interact with anionic pollutants. For CSEUF, a cationic starch was synthesized, whose degree of substitution was 0.2 and water-insoluble. Chromate was bound spontaneously to cationic starch, after that the binding was saturated. As the concentration of cationic starch increased from 0.5 to 1.0, to 1.5, to 2.0, and to 2.5 g/l, the removal of chromate increased from 33% to 62%, to 82%, to 95% and to 98%, respectively. Based on the high removal, high flux, and biodegradability of cationic starch, CSEUF is a feasible process to remove chromate from the aqueous stream
Removal of chlorinated contaminants form surfactant solution for the reuse of surfactant
No full textThe preparation and characterization of micro-sized emulsion using vegetable oils for the remediation of DNAPL
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