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tower stripping, and therefore much lower strip-gas to water flow ratios are needed for an effective stripping. The removal of 12 organic contaminants from water using a HFM module was studied under low strip gas flow to water flow ratios (up to 5:1). Removal efficiencies were found to be strongly dependent on the Henry’s law constants indicating a substantial mass transfer resistance on the gas side. Vacuum can be either used to increase removal efficiencies, or to decrease the amount of strip gas that has to be treated without sacrificing efficiency (Fig. 2). The conventional resistance in series model was inapplicable to predict mass transfer coefficients in our experiments as it assumes, that at least for the operation conditions used here, the liquid side mass transfer resistance dominates the overall resistance for all compounds (Fig. 3, left). Therefore, a new hybrid numerical and analytical modeling approach in the finite element simulator RockFlow/GeoSys for hydraulic flow and mass transport was developed. This approach enables the prediction of the removal efficiencies within a few minutes, whereas a pure numerical approach would require several hours to days due to numerical stability controls. The input parameters for the model are defined by the geometry of the HFM and the operating conditions, no empirical formulations are applied. The model allows the investigation of the main factors controlling the removal characteristics, e.g. the dependency on Henry’s law coefficient, gas side diffusional Kcalc (m/s) 3.0e-5 2.0e-5 1.0e-5 0.0 0.0 1.0e-5 2.0e-5 3.0e-5 K exp (m/s) C/C0 (-) m odel 0.001 0.01 0.1 1 1 0.1 0.01 C/C0 (-) experimental Fig. 3: Left: Calculated overall mass transfer coefficients K vs. experimental K. Calculations based on the resistance in series model. Right: Comparison of the experimental removal efficiencies (C/C0, with C being the outflow aqueous concentration and C0 being the inflow aqueous concentration) with the removal efficiencies calculated by the proposed model. resistance, and aqueous diffusion limitation, and also enables the efficient design of further organic removal systems based on the HFM technology. The model was able to predict removal efficiencies for all experimental conditions with reasonable accuracy (Fig. 3 right). - 142 - 0.001
As the second step of the treatment method, the catalytic conversion of several organic contaminants was studied at elevated temperatures (50°C – 400°C) in the gas phase. In particular, the catalytic hydrodehalogenation of seven aliphatic chlorinated organic compounds (PCE, TCE, cis-1,2-DCE, 1,1-DCE, 1,1,2,2-TCA, 1,2-DCA), and the hydrogenation as well as oxidation of ether compounds used as fuel oxygenates (MTBE, ETBE, TAME, DIPE) was studied over palladium catalysts. In all cases the compounds were transformed to non toxic or less toxic products. Reaction rates were in general pseudo first order and half lives were in the range of milliseconds to seconds, depending on the compound and the temperature. As an example the temperature dependent first order rates obtained for the reductive conversion of chlorinated aliphatic compounds are compiled in Table 1. In general, ethane was the sole degradation product. Table 1: Gas phase reductive catalytic conversion of chlorinated aliphatic compounds using a palladium on alumina catalyst. Rates are reported as sec -1 . T, o C 1,1-DCE c-1,2-DCE TCE PCE 1,1,2,2- TCA 1,2-DCA Chloroethane 50 9.42±0.09 7.91±0.18 4.23±0.18 3.2±0.04 n.d. n.d. n.d. 75 13.4±0.25 11.8±0.40 7.42±0.12 5.82±0.11 n.d. n.d. n.d. 100 18.9±0.46 18.2±0.25 11.9±0.18 9.83±0.10 4.35±0.09 n.d. n.d. 150 29.4±0.54 28.9±0.63 21.8±0.48 19.4±0.25 12.3±0.12 n.d. n.d. 200 n.d. n.d. 38.2±1.35 36.8±0.69 24.2±0.27 1.50±0.05 n.d. 250 n.d. n.d. n.d. n.d. 39.9±0.25 3.14±0.04 2.55±0.06 300 n.d. n.d. n.d. n.d. n.d. 6.13±0.06 5.26±0.15 350 n.d. n.d. n.d. n.d. n.d. 9.48±0.13 9.05±0.11 400 n.d. n.d. n.d. n.d. n.d. n.d. 15.5±0.26 Currently, a container based pilot scale groundwater treatment plant is under construction in cooperation with the Environmental Research Center Leipzig/Halle (UFZ) to advance this technology into real use. - 143 -
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ANNUAL REPORT 2 0 0 6 FACULTY OF MA
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Annual Report 2006 Faculty 11 Mater
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Preface The year 2006 of the Depart
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difference of numerical and analyti
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Institute of Materials Science Phys
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Research Projects Bulk Amorphous Al
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el Dsoki, C.; Landersheim, V. ; Kau
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Das, J.; Kim, K. B.; Xu, W.; Wei, B
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Staff Members Head Prof. Dr. Jürge
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Zhou L.; Rixecker G.; Aldinger F.;
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concerned with the synthesis and ch
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Publications Fleissner, A.; Schmid,
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• Surface analysis The UHV-surfac
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T. Mayer, U. Weiler, E. Mankel and
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Thin films The Thin Film division w
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Berky, W.; Gottschalk, S.; Elliman,
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Guest Scientists Research Projects
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Hesse, S.; Zimmermann, J.; von Segg
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Structure Research The research in
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Research Projects Functional Advanc
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Dincer, I.; Elerman, Y.; Elmali, A;
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hexakis(imidazole)nickel(II)bis(for
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Chemical Analytics The chemical ana
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Collaborations The above mentioned
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Hoffmann, P.; Non-Invasive Identifi
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Ferroelectrics For this class of ma
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Materials Modelling The research ac
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Materials for Renewable Energies In
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Joint Research Laboratory Nanomater
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Collaborative Research Center (SFB)
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B7 P.I.: Prof. H. v. Seggern / Dr.
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The glass transition temperature (T
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transition allows to investigate at
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Relative density 1.00 0.95 0.90 0.8
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Fig. 2 shows the time dependencies
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Dielectric interface trap engineeri
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∆V C q th eff 12 −2 p ( VGS = 0
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Fig. 3: Schematic of the photovolta
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synthesis and analysis of interface
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Fig. 2: Resistivity vs temperature
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Fig. 2: X-ray appearance near-edge
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Capacity [mAhg -1 ] 700 600 500 400
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Texture investigations and field em
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screening effects. Gold coating of
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Figure 2 shows a selected region of
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The spectrum shows that apart from
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