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Article Dans Une Revue Geochimica et Cosmochimica Acta Année : 2010

Reactive transport of gentisic acid in a hematite-coated sand column : Experimental study and modeling

Résumé

The adsorption of gentisic acid (GA) by hematite nano-particles was examined under static and dynamic conditions by conducting batch and column tests. To simulate natural sediments, the iron oxide was deposited on 10 lm quartz particles. The GA adsorption was described by a surface complexation model fitted to pH-adsorption curves with GA concentrations of 0.11 mM in a pH range of 310. The surface was described with one type of site (FeOH), while gentisic acid at the surface was described by two surface complexes (FeLH2, log Kint = 8.9 and FeLH, log Kint = 8.2). Modeling was conducted with PHREEQC-2 using the MINTEQ database. From a kinetic point of view, the intrinsic chemical reactions were likely to be the rate-limiting step of sorption (103 s1) while external and internal mass transfer rates (102 s1) were much faster. Under flow through conditions (column), adsorption of GA to hematite-coated sand was about 7-times lower than under turbulent mixing (batch). This difference could not be explained by chemical adsorption kinetics as shown by test calculations run with HYDRUS-1D software. Surface complexation model simulations however successfully described the data when the surface area was adjusted, suggesting that under flow conditions the accessibility to the reactive surface sites was reduced. The exact mechanism responsible for the increased mobility of GA could not be determined but some parameters suggested that decreased external mass transfer between solution and surface may play a significant role under flow through conditions.

Dates et versions

hal-00509082 , version 1 (10-08-2010)

Identifiants

Citer

K. Hanna, B. Rusch, Laurent Lassabatère, A. Hofmann, B. Humbert. Reactive transport of gentisic acid in a hematite-coated sand column : Experimental study and modeling. Geochimica et Cosmochimica Acta, 2010, 74 (12), pp 3351-3366. ⟨10.1016/j.gca.2010.03.022⟩. ⟨hal-00509082⟩
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