Uranium release from a natural rock under near-natural oxidizing conditions

Abstract

Understanding how uranium (U) moves through the soil and groundwater is essential to determine the effectiveness of cleanup technologies. Uranium release and transport in the subsurface under oxic conditions have been reported to be mostly dependent on sorption onto Fe/Mn-oxide and complex interactions with organic substances. Available information in the literature however presents evidence of U retardation by natural sands. The aim of this investigation was to characterize U dissolution from a uraninite-containing rock (UO 2 -rock) in different waters under test conditions relevant to U transport from mine wastes (tailings). For this purpose, not shaken batch experiments were conducted with a constant amount of an UO 2 -rock and different types of water (deionised, tap and mineral water). For comparison parallel experiments were conducted with 0.1 M Na 2 CO 3 and 0.1 M H 2 SO 4 . Further dissolution experiments using UO 2 -rock together with dolomite and pyrite were conducted.The results indicate that carbonate addition (soluble or in-situ generated) enhanced U 2 solubilization, whereas pyrite addition essentially slowed the initial U solubilization. It is shown that SiO 2 and other rock constituents may contribute to retard U transport.

Groundwater Quality

“…No carbon-14 or krypton-85 was detected in the monitoring well, suggesting preferential retention or volatilization during transit to the water table. Noubactep et al (2006) demonstrated that carbonate addition enhanced uranium solubilization, while pyrite addition slowed initial uranium solubilization. Silicon dioxide and other rock constituents were found to retard uranium transport.…”

Characterizing As, Cu, Fe and U Solubilization by Natural Waters

“…Furthermore, the objective was not to achieve any steady state (pseudo-equilibrium) but rather to compare contaminant solubilization under different conditions. Previous studies (e.g., Noubactep et al 2006) showed that while using essay tubes of about 20 mL capacity and tap water a leaching time of 14 days (336 hours) was sufficient to achieve reproducible leaching results in non-disturbed experiments. The suitability of this leaching time was verified in preliminary works by investigating the effect of material particle size on the extent of contaminant release from each material (including CuFeS 2 -next section).…”

Uranium, Mining and Hydrogeology

“…Previous studies (e.g., Noubactep et al 2006) showed that while using essay tubes of about 20 mL capacity and tap water a leaching time of 14 days (336 hours) was sufficient to achieve reproducible leaching results in non-disturbed experiments. In the present study no effort was done to accelerate mass transfer.…”