Interpretation of REE patterns in natural water based on the stability constants

Yamamoto, Yuki; Takahashi, Yoshio; Shimizu, Hiroshi

doi:10.1016/j.gca.2006.06.1587

Cited by 15 publications

(19 citation statements)

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“…(1)-(4) are quite different for the HREE (on average, standard deviation are as high as 0.41). Recently published experimental results for REE complexation with FA and HA (Yamamoto et al, 2005(Yamamoto et al, , 2006 suggest that the log K values for REE complexation with HM should vary across the REE series in an analogous way to the log K values for AA. Moreover, Wood (1993) pointed out that AA likely represents a model system for simple carboxylic sites on more complex organic matter, such as HM.…”

Section: Estimating Constant Values For the Reementioning

confidence: 97%

“…Moreover, Wood (1993) pointed out that AA likely represents a model system for simple carboxylic sites on more complex organic matter, such as HM. Carboxylic groups could thus be the major sites by which REE are bound to HM (Yamamoto et al, 2005(Yamamoto et al, , 2006.…”

Section: Estimating Constant Values For the Reementioning

confidence: 99%

“…For that purpose, we require REE binding constants for REE-proton exchange with humic matter (HM). These constants can be experimentally determined, either for individual REE (e.g., Bidoglio et al, 1991;Moulin et al, 1992;Lead et al, 1998;Lippold et al, 2005) or for the whole REE series (Yamamoto et al, 2005;Sonke and Salters, 2006;Yamamoto et al, 2006). However, experimentally determined REE constants may be difficult to use because of differences in the pH and/or ionic strength conditions of the experiments (Bidoglio et al, 1991;Moulin et al, 1992;Lead et al, 1998;Lippold et al, 2005) or due to differences in the REE/HM ratio of the experimental solutions (Yamamoto et al, 2005;Sonke and Salters, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Organic complexation of rare earth elements in natural waters: Evaluating model calculations from ultrafiltration data

Pourret

Davranche

Gruau

et al. 2007

Geochimica et Cosmochimica Acta

105

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The Stockholm Humic Model (SHM) and Humic Ion-Binding Models V and VI were compared for their ability to predict the role of dissolved organic matter (DOM) in the speciation of rare earth elements (REE) in natural waters. Unlike Models V and VI, SHM is part of a speciation code that also allows us to consider dissolution/precipitation, sorption/desorption and oxidation/reduction reactions. In this context, it is particularly interesting to test the performance of SHM. The REE specific equilibrium constants required by the speciation models were estimated using linear free-energy relationships (LFER) between the first hydrolysis constants and the stability constants for REE complexation with lactic and acetic acid. Three datasets were used for the purpose of comparison: (i) World Average River Water (Dissolved Organic Carbon (DOC) = 5 mg L À1 ), previously investigated using Model V, was reinvestigated using SHM and Model VI; (ii) two natural organic-rich waters (DOC = 18-24 mg L À1 ), whose REE speciation has already been determined with both Model V and ultrafiltration studies, were also reinvestigated using SHM and Model VI; finally, (iii) new ultrafiltration experiments were carried out on samples of circumneutral-pH (pH 6.2-7.1), organic-rich (DOC = 7-20 mg L À1 ) groundwaters from the Kervidy-Naizin and Petit-Hermitage catchments, western France. The results were then compared with speciation predictions provided by Model VI and SHM, successively. When applied to World Average River Water, both Model VI and SHM yield comparable results, confirming the earlier finding that a large fraction of the dissolved REE in rivers occurs as organic complexes This implies that the two models are equally valid for calculating REE speciation in low-DOC waters at circumneutral-pH. The two models also successfully reproduced ultrafiltration results obtained for DOC-rich acidic groundwaters and river waters. By contrast, the two models yielded different results when compared to newly obtained ultrafiltration results for DOC-rich (DOC > 7 mg L À1 ) groundwaters at circumneutral-pH, with Model VI predictions being closer to the ultrafiltration data than SHM. Sensitivity analysis indicates that the ''active DOM parameter'' (i.e., the proportion of DOC that can effectively complex with REE) is a key parameter for both Model VI and SHM. However, a survey of ultrafiltration results allows the ''active DOM parameter'' to be precisely determined for the newly ultrafiltered waters studied here. Thus, the observed discrepancy between SHM predictions and ultrafiltration results cannot be explained by the use of inappropriate ''active DOM parameter'' values in this model. Save this unexplained discrepancy, the results presented in this study demonstrate that both Model VI and SHM can provide reliable estimates of REE speciation in organic-rich waters. However, it is essential to know the proportion of DOM that can actively complex REE before running these two speciation models.

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Section: Estimating Constant Values For the Reementioning

confidence: 97%

Section: Estimating Constant Values For the Reementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Organic complexation of rare earth elements in natural waters: Evaluating model calculations from ultrafiltration data

Pourret

Davranche

Gruau

et al. 2007

Geochimica et Cosmochimica Acta

105

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“…Several recent studies showed that determining such constants is not an easy task because of the presence of a possible metal loading effect, leading to variations in the log K REE d patterns with variations in REE/HA ratio. Thus, Yamamoto et al (2005Yamamoto et al ( , 2006 and Pourret et al (2007b) reported a middle-REE (MREE) downward concavity in the log K REE d patterns from complexation experiments conducted at high metal loading (i.e. REE/C molar ratio ranging from 10 À3 to 1.5 Â 10 À2 , with C corresponding to the amount of organic carbon).…”

Section: Introductionmentioning

confidence: 95%

“…There is now ample evidence that humic substances (HS) control REE speciation in natural organic-rich waters (Bidoglio et al, 1991;Takahashi et al, 1997;Glaus et al, 1995Glaus et al, , 2000Viers et al, 1997;Dia et al, 2000;Gruau et al, 2004;Johannesson et al, 2004;Davranche et al, 2005Davranche et al, , 2008Yamamoto et al, 2005Yamamoto et al, , 2006Sonke and Salters, 2006;Pourret et al, 2007a,b;Stern et al, 2007;Pédrot et al, 2008). Speciation studies show that nearly 100% of the REE occur as organic complexes in such waters (Viers et al, 1997;Dia et al, 2000;Tang and Johannesson, 2003;Gruau et al, 2004;Johannesson et al, 2004;Pourret et al, 2007b;Pédrot et al, 2008).…”

Section: Is There Any Evidence For a Metal Loading Effect In Natural mentioning

confidence: 99%

Metal loading effect on rare earth element binding to humic acid: Experimental and modelling evidence

Marsac

Davranche

Gruau

et al. 2010

Geochimica et Cosmochimica Acta

111

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International audienceThe effect of metal loading on the binding of rare earth elements (REE) to humic acid (HA) was studied by combining ultrafiltration and Inductively Coupled Plasma Mass Spectrometry techniques. REEHA complexation experiments were performed at pH 3 for REE/C molar ratios ranging from ca 4 — 10-4 to 2.7 — 10-2. Results show that the relative amount of REE bound to HA strongly increases with decreasing REE/C. A middle-REE (MREE) downward concavity is shown by patterns at high metal loading, whereas patterns at low metal loading display a regular increase from La to Lu. Humic Ion Model VI modelling are close to the experimental data variations, provided that (i) the ?LK2 parameter (i.e. the Model VI parameter taken into account the presence of strong but low density binding sites) is allowed to increase regularly from La to Lu (from 1.1 to 2.1) and (ii) the published log KMA values (i.e. the REEHA binding constants specific to Model VI) are slightly modified, in particular with respect to heavy REE. Modelling approach provided evidence that patterns with varying REE/C likely arises because REE binding to HA occurs through two types of binding sites in different density: (i) a few strong sites that preferentially complex the heavy REE and thus control the atterns at low REE/C; (ii) a larger amount of weaker binding sites that preferentially complex the middle-REE and thus control the pattern at high REE/C. Hence, metal loading exerts a major effect on HA-mediated REE binding, which could explain the diversity of published conditional constants for REE binding with HA. A literature survey suggests that the few strong sites activated at low REE/C could be multidentate carboxylic sites, or perhaps N-, or P-functional groups. Finally, an examination of the literature field data proposed that the described loading effect could account for much of the variation in REE patterns observed in natural organic-rich waters (DOC > 5 mg L-1 and 4 pH 7)

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Complexation of Sn with Boom Clay natural organic matter under nuclear waste repository conditions

Durce

Salah

Wang

et al. 2020

Applied Geochemistry

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Interpretation of REE patterns in natural water based on the stability constants

Cited by 15 publications

References 0 publications

Organic complexation of rare earth elements in natural waters: Evaluating model calculations from ultrafiltration data

Organic complexation of rare earth elements in natural waters: Evaluating model calculations from ultrafiltration data

Metal loading effect on rare earth element binding to humic acid: Experimental and modelling evidence

Complexation of Sn with Boom Clay natural organic matter under nuclear waste repository conditions

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