Sorption equilibrium and kinetics of NpO₂⁺on dispersed particles of Na-montmorillonite

Abstract

NpO 2 + / Sorption / Na-montmorillonite / Affinity spectrum / Kinetic spectrum Summary. Sorption equilibrium and kinetics of NpO 2 + on dispersed particles of Na-montmorillonite were experimentally investigated by using a batch technique and a spectroscopic method, respectively. Considering the heterogeneity of sorption sites, we investigated the affinity spectra for the sorption of NpO 2 + . It was found that the spectrum for NpO 2 + was monomodal but asymmetrical and that the half-width at half-maximum of the spectrum was relatively broad, indicating that the sorption sites of surface of Na-montmorillonite are strongly heterogeneous. From the kinetic spectrum for NpO 2 + , two sorption processes could be distinguished. It was considered that the fast process is attributable to the sorption of NpO 2 + on the easily accessible outer surface of Na-montmorillonite particles and that the slower process is assigned to the sorption on the interlayer surface. Mean apparent activation enthalpies for the fast and the slow processes were evaluated as 19 ± 2 kJ/mol and 23 ± 3 kJ/mol, respectively.

Neptunium(V) sorption on kaolinite

“…Additionally, the solution chemistry of Np(V) can serve as a guide for that of Pu(V), whose instability towards disproportionation and reduction complicates experimental investigations. Many studies have investigated the behavior of Np(V) sorption onto clays, such as montmorillonite [25][26][27][28][29], smectite [30], bentonite [31], and Opalinus clay [32]. It has been found that the sorption of Np(V) depends on many parameters, such as pH value [27,31,32], Np(V) concentration [28,32], electrolyte concentration [33], and carbonate concentration [27,32].…”

Sorption of neptunium(V) on Opalinus Clay under aerobic/anaerobic conditions

“…Many studies have investigated the sorption behaviour of Np(V) on different clay minerals, such as kaolinite [11,12], or smectite [13][14][15][16]. Sorption of Np(V) was found to depend on several factors, such as pH [11,13], Np concentration [11,14], partial pressure of CO 2 [11,13], and ionic strength [11].…”

“…Sorption of Np(V) was found to depend on several factors, such as pH [11,13], Np concentration [11,14], partial pressure of CO 2 [11,13], and ionic strength [11]. Only few studies on Np(V) sorption under higher partial pressures of CO 2 are reported.…”

Structural identification of europium(iii) adsorption complexes on montmorillonite

“…This solid has been chosen because it could be a mineral representative of natural clay, which might be used as an engineered barrier thanks to its low permeability and its high sorption capacity. Up to now, many studies have been published on the retention properties of such a mineral, [27][28][29][30][31][32][33][34][35][36] but only a few have been devoted to a complete study combining both macroscopic and microscopic points of view.…”