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@PHDTHESIS{Kasel:150786,
      author       = {Kasel, Daniela},
      title        = {{T}ransport and deposition of functionalized multi-walled
                      carbon nanotubes in porous media},
      volume       = {201},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2014-00831},
      isbn         = {978-3-89336-929-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {VI, 103 S.},
      year         = {2013},
      note         = {RWTH Aachen, Diss., 2013},
      abstract     = {The aim of this study was to gain more profound knowledge
                      on the transport anddeposition of functionalized
                      multi-walled carbon nanotubes (MWCNTs) in porous media. The
                      use of $^{14}$C-labeled MWCNTs allowed investigations into
                      very low concentrations and the determination of retention
                      profiles. Transmission electron micrographs revealed that
                      the MWCNTs exhibited average outer diameters of 10–50 nm
                      and average lengths of up to several $\mu$m. The
                      functionalization of the MWCNTs with nitric acid induced
                      oxygen containing functional groups and reduced the amount
                      of metal catalysts on the nanotubes. Since nanoparticles do
                      not behave like solutes but rather like colloids, the
                      applicability of the available experimental setups and
                      procedures was evaluated for carbon nanotubes. The
                      nanoparticles could not be injected using a sample loop or
                      an irrigation head. Therefore,the MWCNTs were applied to the
                      columns directly by a pump or a pipette, respectively. The
                      effect of the input concentration (C$_{o}$) and sand grain
                      size on the transport andretention of MWCNTs was
                      investigated in water-saturated sand columns at conditions
                      unfavorable for attachment (repulsive electrostatic forces).
                      These experiments were performed at very low C$_{o}$
                      (0.005–1 mg L$^{-1}$), low ionic strength (1 mM KCl), and
                      high flowrate (0.64 cm min$^{-1}$). The breakthrough curves
                      (BTCs) for MWCNTs typically did notreach a plateau, but
                      exhibited an asymmetric shape that slowly increased during
                      breakthrough. The retention profiles (RPs) exhibited a
                      hyper-exponential shape with greater retention near the
                      column inlet. The collected BTCs and RPs were simulated
                      using a numerical model within the HYDRUS-1D code that
                      accounted for both time- and depth-dependent blocking
                      functions on the retention coefficient. For a given C$_{o}$,
                      the depth-dependent retention coefficient and the maximum
                      solid phase concentration of MWCNTs were both found to
                      increase with decreasing grain size. These trends reflect
                      greater MWCNTs retention rates and a greater number of
                      retention locations in the finer textured sand. The
                      normalized concentration of MWCNTs in the effluent increased
                      and the RPsbecame less hyper-exponential with higher Co due
                      to enhanced blocking/filling of retention locations. This
                      concentration dependency of MWCNT transport increased with
                      smaller grain size because of the effect of pore structure
                      and the shape of MWCNTs on their retention. In particular,
                      MWCNTs have a high aspect ratio, and it was hypothesized
                      that MWCNTs may create a porous network with an enhanced
                      ability to retain further MWCNTs, especially in smaller
                      grain-sized sand and at higher C$_{o}$. Results demonstrate
                      that model simulations should accurately account for
                      observed behavior of both BTCs andRPs to make reliable
                      predictions on MWCNT transport.},
      keywords     = {Dissertation (GND)},
      cin          = {IBG-3},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {245 - Chemicals in the Environment (POF2-245)},
      pid          = {G:(DE-HGF)POF2-245},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/150786},
}