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Sökning: swepub > Örebro universitet > Linköpings universitet > Borén Hans

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1.
  • Dahlén, Johan, 1969-, et al. (författare)
  • Determination of the molecular weight of fulvic acids by UV/VIS spectroscopy
  • 1999
  • Ingår i: Chemosphere. - 0045-6535. ; 38:4, s. 783-794
  • Tidskriftsartikel (refereegranskat)abstract
    • Partial least squares (PLS) modeling was applied to investigate number-average molecular weights (Mn) and weight-average molecular weights (Mw) of fulvic acids (FAs) in relation to the corresponding UVNIS spectra. The Mn and Mw values were determined by size exclusion chromatography (SEC). The impact of pH control, wavelength range and density as well as smoothing and derivation of spectra were tested. It was found that PLS models based on absorbance spectra can be a fast and powerful complement to existing techniques employed for determination of molecular weights of FAs. Control of pH of the FA solutions is important for the performance of the models. The models were also compared with the best univariate alternatives.
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2.
  • Johansson, Inger, et al. (författare)
  • Analysis of water leachable organic components in incineration residues
  • 2000
  • Ingår i: International Journal of Environmental Analytical Chemistry. - 0306-7319. ; 78:3-4, s. 305-313
  • Tidskriftsartikel (refereegranskat)abstract
    • The composition of water leachable organics in municipal solid waste incineration (MSWI) residues is not well known. Therefore the utilisation of ashes is restricted due to the concern about their long-term environmental impact. Previous studies have focused on some highly toxic organic compounds present only in trace amounts. It is also important to know the composition of the bulk organic matter since dissolved organic carbon can alter the leachability of metals. In order to characterise water leachable organic matter in incineration residues a fractionation procedure using polymeric adsorbents was successfully developed and applied. The technique uses XAD-8 and XAD-4 resins in tandem and has been implemented on bottom ash samples from two incineration plants in Sweden in order to characterise the bulk organic matter.
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3.
  • Pavasars, Ivars, et al. (författare)
  • Alkaline degradation of cellulose : mechanisms and kinetics
  • 2003
  • Ingår i: Journal of polymers and the environment. - 1566-2543. ; 11:2, s. 39-47
  • Tidskriftsartikel (refereegranskat)abstract
    • Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70-85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150-550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.
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  • Resultat 1-3 av 3
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tidskriftsartikel (3)
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refereegranskat (3)
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Allard, Bert (3)
Pavasars, Ivars (2)
Bäckström, Mattias, (1)
Johansson, Inger, (1)
Hagberg, Jessika, (1)
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Dahlén, Johan, 1969- ... (1)
Ephraim, James (1)
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Engelska (3)
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