% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Brandt:202213,
      author       = {Brandt, F. and Curti, E. and Klinkenberg, M. and Rozov, K.
                      and Bosbach, D.},
      title        = {{R}eplacement of barite by a ({B}a,{R}a){SO}4 solid
                      solution at close-to-equilibrium conditions: {A} combined
                      experimental and theoretical study},
      journal      = {Geochimica et cosmochimica acta},
      volume       = {155},
      issn         = {0016-7037},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2015-04502},
      pages        = {1 - 15},
      year         = {2015},
      abstract     = {Solid solution formation between RaSO4 and BaSO4 has long
                      been recognized as a process which potentially controls the
                      Raconcentration in the environment. Here, we have
                      systematically studied the replacement of pure barite by a
                      (Ba,Ra)SO4 solidsolution in 0.1 M NaCl through batch
                      experiments extending up to 883 days at close-to-equilibrium
                      (CTE) conditions, whichare relevant to disposal of nuclear
                      waste in a deep geological repository. Kinetic and
                      thermodynamic models were applied tosupport the
                      interpretation of the experiments, which were carried out at
                      room temperature and at two distinct solid/liquid ratio(0.5
                      or 5 g/L). Different stages of recrystallization were
                      observed, based on the rate of removal of Ra from aqueous
                      solution.After a first slow kinetic step, a change in the
                      slope of the aqueous Ra concentration vs. time is observed,
                      suggesting nucleationof a new (Ba,Ra)SO4 phase from
                      supersaturation. If this stage was considered to reflect
                      equilibrium between aqueous and solidsolution, one would
                      infer ideality or even negative interaction parameters (a0 6
                      0). After this fast nucleation step, in the 0.5
                      g/Lexperiments the Ra concentrations in the aqueous solution
                      slowly increase, approaching a concentration close to that
                      requiredfor equilibrium with a regular (Ba,Ra)SO4 solid
                      solution with an interaction parameter a0 = 1.0. Therefore,
                      these data suggest anon-equilibrium Ra entrapment during the
                      nucleation phase of the replacement, followed by slow
                      recrystallization toward truethermodynamic solid solution
                      equilibrium. Moreover, an interaction parameter value of a0
                      = 1.0 was inferred from our experiments,which is in good
                      agreement with theoretical predictions from atomistic
                      simulations.A key result from this study is that aqueous
                      solution and binary (Ba,Ra)SO4 approach full thermodynamic
                      equilibriumwithin laboratory time scales (2.5 years). This
                      justifies assuming complete thermodynamic equilibrium for
                      this system in geochemicalcalculations of processes
                      occurring on geological time scales. This finding is of
                      direct relevance for the safety assessmentof radioactive
                      waste disposal, since it may constrain the solubility and
                      thus the mobility of Ra in such environments.},
      cin          = {IEK-6},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-6-20101013},
      pnm          = {161 - Nuclear Waste Management (POF3-161) / SKIN - Slow
                      processes in close-to-equilibrium conditions for
                      radionuclides in water/solid systems of relevance to nuclear
                      waste management (269688)},
      pid          = {G:(DE-HGF)POF3-161 / G:(EU-Grant)269688},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000351732800001},
      doi          = {10.1016/j.gca.2015.01.016},
      url          = {https://juser.fz-juelich.de/record/202213},
}