Sorption of Eu(III) on Granite: EPMA, LA–ICP–MS, Batch and Modeling Studies

Abstract

Eu(III) sorption on granite was assessed using combined microscopic and macroscopic approaches in neutral to acidic conditions where the mobility of Eu(III) is generally considered to be high. Polished thin sections of the granite were reacted with solutions containing 10 μM of Eu(III) and were analyzed using EPMA and LA-ICP-MS. On most of the biotite grains, Eu enrichment up to 6 wt % was observed. The Eu-enriched parts of biotite commonly lose K, which is the interlayer cation of biotite, indicating that the sorption mode of Eu(III) by the biotite is cation exchange in the interlayer. The distributions of Eu appeared along the original cracks of the biotite. Those occurrences indicate that the prior water-rock interaction along the cracks engendered modification of biotite to possess affinity to the Eu(III). Batch Eu(III) sorption experiments on granite and biotite powders were conducted as functions of pH, Eu(III) loading, and ionic strength. The macroscopic sorption behavior of biotite was consistent with that of granite. At pH > 4, there was little pH dependence but strong ionic strength dependence of Eu(III) sorption. At pH < 4, the sorption of Eu(III) abruptly decreased with decreased pH. The sorption behavior at pH > 4 was reproducible reasonably by the modeling considering single-site cation exchange reactions. The decrease of Eu(III) sorption at pH < 4 was explained by the occupation of exchangeable sites by dissolved cationic species such as Al and Fe from granite and biotite in low-pH conditions. Granites are complex mineral assemblages. However, the combined microscopic and macroscopic approaches revealed that elementary reactions by a single mineral phase can be representative of the bulk sorption reaction in complex mineral assemblages.

Sorption of Eu(III) on Eibenstock granite studied by µTRLFS: A novel spatially-resolved luminescence-spectroscopic technique

“…Biotite is mainly accumulating trivalent radionuclides in the interlayer by exchanging them for K + . It remains unclear whether this occurs as inner or outer sphere complexes 13 . This sorption process starts at pH 2.5 and reaches its maximum at pH 3.5.…”

“…To understand how the described heterogeneities influence the sorption behavior of granite, it is necessary to study the real system directly, maintaining the species-mineral relationship, which can only be achieved by spatially-resolved investigations. However, most spatially-resolved studies of radionuclide migration focus on the quantitative distribution of radionuclides and their analogues 21 , often resorting to co-location with other elements to obtain further information 13,22–24 . If the speciation of the adsorbate cannot be determined in the spatially-resolved experiment directly, one must rely on correlation with results from single phase studies to deduce the mineral-species relationship.…”

“…If the speciation of the adsorbate cannot be determined in the spatially-resolved experiment directly, one must rely on correlation with results from single phase studies to deduce the mineral-species relationship. Studies of Eu 3+ sorption on granite with electron probe micro analysis (EPMA) and laser-ablation ICP-MS (LA-ICP-MS) 13,21 at low to neutral pH show a heterogeneous distribution, mostly on biotite, which is affected by its topology and alteration during the sorption process. There is also an accumulation of the metal ions at grain boundaries between quartz and feldspar 13 .…”

Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides: Effect of microbial cells on the oxidation of trivalent cerium

“…Most REEs exhibit a trivalent oxidation state in the ambient environment. Trivalent REEs are readly adsorbed by inorganic and organic compounds such as metal oxides, hydroxides, minerals, clay minerals, microbial cells, cellulose, and resins (Coppin et al, 2002;Rabung et al, 2005;Ozaki et al, 2006;Ishida et al, 2009;Takahashi et al, 2010;Tang and Johannesson, 2010;Estes et al, 2013;Fukushi et al, 2013). Metal oxides such as Mn oxides are well known to accumulate large amounts of trivalent REEs under conditions encountered in deep-sea ferromanganese crusts and nodules (Piper, 1974;De Carlo and McMurtry, 1992;Bau et al, 1996;Ohta et al, 1999;Bau and Koschinsky, 2009).…”

Comparative adsorption of Eu(iii) and Am(iii) on TPD

“…1,[8][9][10][11][12] Therefore, the behaviors of Eu(III) on oxide mineral, clay, granite, and soil were widely adapted to extrapolate the transport behaviors of Am(III) and other actinides. 1,[8][9][10][11][12] Therefore, the behaviors of Eu(III) on oxide mineral, clay, granite, and soil were widely adapted to extrapolate the transport behaviors of Am(III) and other actinides.…”