Experimental studies of REE fractionation during water–mineral interactions: REE release rates during apatite dissolution from pH 2.8 to 9.2

An experimental study of the dissolution rates of Nd-britholite, an apatite-structured actinide-bearing waste storage host analogue

“…The low Nd release rate and the relatively low phosphorus release suggest Nd retention by the precipitation of a neodymium phosphate phase. Secondary rare-earth element phosphates were also observed to precipitate during the dissolution of apatite [28,31], monazite and xenotime [32], granites [33][34][35], rare-earth element/thorium phosphate diphosphate solid solutions [36], and nuclear waste glass [37]. The rare-earth phosphate phase precipitated in these studies is commonly identified as rhabdophane (REE(PO 4 ) AE nH 2 O) due to its estimated solubility product.…”

“…Dissolution rates were measured in open-system, mixed-flow reactors consisting of 120 ml Savillex Ò fusion vessels [28]. These reactors were fitted with Nalgene Ò tubes for inlet and outlet fluid passage.…”

Submarine groundwater discharge of rare earth elements to a tidally-mixed estuary in Southern Rhode Island

“…For example, the presence of trace amounts of phosphate impurities in the REE phosphate minerals used in the solubility experiments could alter the REE/P ratio in the dissolving fluid, leading to higher PO 4 3− than Ln 3+ concentrations in the experimental solutions (Centiner et al, 2005). Furthermore, Köhler et al (2005) noted that during apatite dissolution experiments, secondary phosphate minerals such as rhabdophane precipitated. Because rhabdophane has an affinity for the LREEs, the precipitation of LREE enriched secondary phosphates like rhabdophane during such experiments could affect the solubility constant calculations if stoichiometric dissolution is assumed.…”

“…The relative enrichment of MREEs in Pettaquamscutt groundwaters by apatite weathering may be further enhanced by the precipitation of LREE bearing, secondary phosphate minerals such as rhabdophane and florencite (Banfield and Eggleton, 1987;Braun et al, 1990Braun et al, , 1998. For example, during rhabdophane precipitation, the LREEs between Ce and Eu are preferentially removed from solution relative to heavier REEs (Köhler et al, 2005).…”

The experimental determination of REE partition coefficients in the water-calcite system

“…As a result of their systematic electron configuration, they exhibit a relatively similar chemical behaviour. Their gradually varying ionic size, however, leads to distinct REE concentration patterns stemming from their aqueous complexation and their varying ability to incorporate into and/or adsorb onto solid phases (e.g., Elderfield, 1988;Elderfield et al, 1990;Köhler et al, 2005;Lipin and McKay, 1989;Schnetzler and Philpotts, 1970). Due to their ability to incorporate REE and their widespread distribution in sedimentary rocks, the REE content of biogenic (e.g., Azmy et al, 2011;Nothdurft et al, 2004;Palmer, 1985;Sholkovitz and Shen, 1995;Webb and Kamber, 2000) and abiogenic carbonates (Parekh et al, 1977) have been used as paleo-proxies for past seawater compositions, its redox state, and its input sources.…”