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@ARTICLE{Kasel:133626,
      author       = {Kasel, Daniela and Bradford,S.A. and Simunek,Jiri and
                      Heggen, Marc and Vereecken, Harry and Klumpp, Erwin},
      title        = {{T}ransport and retention of multi-walled carbon nanotubes
                      in saturated porous media: {E}ffects of input concentration
                      and grain size},
      journal      = {Water research},
      volume       = {47},
      number       = {2},
      issn         = {1879-2448},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2013-02041},
      pages        = {933-944},
      year         = {2013},
      abstract     = {Water-saturated column experiments were conducted to
                      investigate the effect of input concentration (Co) and sand
                      grain size on the transport and retention of low
                      concentrations (1, 0.01, and 0.005 mg L−1) of
                      functionalized 14C-labeled multi-walled carbon nanotubes
                      (MWCNT) under repulsive electrostatic conditions that were
                      unfavorable for attachment. The breakthrough curves (BTCs)
                      for MWCNT typically did not reach a plateau, but had an
                      asymmetric shape that slowly increased during breakthrough.
                      The retention profiles (RPs) were not exponential with
                      distance, but rather exhibited a hyper-exponential shape
                      with greater retention near the column inlet. The collected
                      BTCs and RPs were simulated using a numerical model that
                      accounted for both time- and depth-dependent blocking
                      functions on the retention coefficient. For a given Co, the
                      depth-dependent retention coefficient and the maximum solid
                      phase concentration of MWCNT were both found to increase
                      with decreasing grain size. These trends reflect greater
                      MWCNT retention rates and a greater number of retention
                      locations in the finer textured sand. The fraction of the
                      injected MWCNT mass that was recovered in the effluent
                      increased and the RPs became less hyper-exponential in shape
                      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 MWCNT shape on MWCNT retention. In
                      particular, MWCNT have a high aspect ratio and we
                      hypothesize that solid phase MWCNT may create a porous
                      network with enhanced ability to retain particles in smaller
                      grain sized sand, especially at higher Co. Results
                      demonstrate that model simulations of MWCNT transport and
                      fate need to accurately account for observed behavior of
                      both BTCs and RPs.},
      cin          = {PGI-5 / IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)IBG-3-20101118},
      pnm          = {424 - Exploratory materials and phenomena (POF2-424)},
      pid          = {G:(DE-HGF)POF2-424},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000315072600045},
      doi          = {10.1016/j.watres.2012.11.019},
      url          = {https://juser.fz-juelich.de/record/133626},
}