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Article Dans Une Revue Geochimica et Cosmochimica Acta Année : 2011

An improved description of the interactions between rare earth elements and humic acids by modeling: PHREEQC-Model VI coupling

Remi Marsac
Mélanie Davranche
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Gérard Gruau
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Martine Bouhnik-Le Coz
Aline Dia

Résumé

An improved description of the interactions between rare earth 1 elements and humic acids by modeling: 2 PHREEQC-Model VI coupling 3 4Abstract-The Humic Ion Binding Model VI (Model VI)-previously used to model the 26 equilibrium binding of rare earth elements (REE) by humic acid (HA)-was modified to 27 account for differences in the REE constant patterns of the HA carboxylic and phenolic 28 groups, and introduced into PHREEQC to calculate the REE speciation on the HA binding 29 sites. The modifications were shown to greatly improve the modeling. They allow for the first 30 time to both satisfactorily and simultaneously model a large set of multi-REE experimental 31 data with the same set of equations and parameters. The use of PHREEQC shows that the 32 light rare earth elements (LREE) and heavy rare earth elements (HREE) do not bind to HA by 33 the same functional groups. The LREE are preferentially bound to carboxylic groups, whereas 34 the HREE are preferentially bound to carboxy-phenolic and phenolic groups. This binding 35 differentiation might lead to a fractionation of REE-HA patterns when competition between 36 REE and other metals occur during complexation. A survey of the available data shows that 37 competition with Al 3+ could lead to the development of HREE-depleted HA patterns. This 38 new model should improve the hydrochemical modeling of the REE since PHREEQC takes 39 into account chemical reactions such as mineral dissolution/precipitation equilibrium and 40 redox reactions, but also models kinetically controlled reactions and one-dimensional 41 transport. 42 43
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hal-01904313 , version 1 (24-10-2018)

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Remi Marsac, Mélanie Davranche, Gérard Gruau, Martine Bouhnik-Le Coz, Aline Dia. An improved description of the interactions between rare earth elements and humic acids by modeling: PHREEQC-Model VI coupling. Geochimica et Cosmochimica Acta, 2011, 75 (19), pp.5625 - 5637. ⟨10.1016/j.gca.2011.07.009⟩. ⟨hal-01904313⟩
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