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At least 235 records · Page 13Linked to original sources
PubMed1994

Radiological implications of readings with a NaI(Tl) monitor set on an ion exchange resin column for purifying primary coolant water.

Changes in readings of a NaI(Tl) monitor set on the surface of an ion exchange resin column used to purify primary coolant water at the Kyoto University Research Reactor were examined with mathematical models to clarify the radiological meanings. The concentration distributions of the nuclides in the interstitial water of the resin bed and those adsorbed on the resins were determined by use of the dispersion-convection theory coupled with the linear isotherm adsorption relation. The adsorbed amount that was assessed by this model was theoretically related to that made by a compartmental model. The buildup concentrations of nuclides in the core water and the decreased accompanying power operation and shut-down were modeled using the value representing the cleanup rate by the purification circuit. The values of this parameter were determined by the least squares method for observed concentrations of 24Na, a major radionuclide in the core water. Recognizing that the adsorption band had remained within the top 10 cm during the circulation of water through the column, the change in the amount of radionuclide adsorbed on the resin was calculated using a compartmental model. The amount of radionuclide adsorbed on the resin predicted by the model agreed well with the readings of the NaI(TI) monitor. Factors that affect the reading are discussed in relation to early detection of fuel defects.

Adsorption↗
PubMed2001

Detoxification of lignocellulose hydrolysates with ion-exchange resins.

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD-8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the anion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.

Cellulose↗