Uranium speciation in weathered granitic waste rock piles: an XAFS investigation

Abstract

Uranium speciation determined by XAFS reveals its retention in weathered waste rock piles by the formation of stable secondary uranium complexes.

Speciation of Uranium and Plutonium From Nuclear Legacy Sites to the Environment: A Mini Review

“…Even in studies in which XANES spectra for extremely low uranium concentrations were obtained (Zhang et al, 2016 ), the U content is about 40 ppm, which is not always the case for the contaminated soils. Few applications of advanced techniques for the identification of U species in the environment are available (Tayal et al, 2019 ). This research should be continued, but destructive analyses will inevitably have to be used to identify uranium partitioning in mobile fractions as they are often the only methods for determining the forms of uranium; see Qiao et al ( 2012 ) and Skipperud et al ( 2013 ).…”

A multi-technique study of altered granitic rock from the Krunkelbach Valley uranium deposit, Southern Germany

“…and U(VI) species immobilized on clay minerals. 29 Different secondary U species, i.e. uranocircite, and metazeunerite, dominate in the area of the Krunkelbach U deposit resulting aer high Ba (higher Ba/Ca ratio) and As contents in the groundwaters and their preferential xation on altered uraninite.…”

“…Both synchrotron and laboratory methods are extensively used separately and in combination for investigations of structural, redox and degradation properties of U minerals. 18,20,23,[28][29][30] Whilst synchrotron methods provide robust and fast analysis with higher sample penetration depth for elemental mapping and speciation as low as few tens of ppm for some heavier metals, e.g. uranium, laboratory tools provide more detailed analysis of the sample's morphology and more detailed speciation.…”

“…Both synchrotron and laboratory methods are extensively used separately and in a combination for investigations of structural, redox and degradation properties of U minerals. 18,20,23,[28][29][30] The use of combined experimental approach is often preferred due to the intricate U speciation in environmental systems which helps to develop optimal strategies for contaminated site remediation. 31,32 Synchrotron methods provide robust and fast analysis with deep sample penetration depth for elemental mapping and speciation while laboratory tools give more detailed analysis on sample´s morphology and more detailed speciation.…”

Geochemical Controls on Uranium Release from Neutral-pH Rock Drainage Produced by Weathering of Granite, Gneiss, and Schist

“…The interplay of Reactions (1) to (3) has important ramifications for U behavior in sulfideand carbonate-bearing mine wastes, yet their cumulative outcome on net U mobility is uncertain. Although there are many studies of U geochemistry in mine wastes, these have predominantly focused on acidic drainage (pH < 6) where CCU complexation is negligible [12,18,19,[27][28][29][30][31][32][33][34][35][36][37]. Neutral-rock drainage (NRD) (e.g., pH ≥ 6 [38]) is typically characterized by high alkalinity (hundreds of mg/L as CaCO 3 ) and dissolved Ca reaching hundreds of mg/L, i.e., orders-of-magnitude above typical fresh groundwaters [39][40][41][42][43][44].…”