REE speciation in low-temperature acidic waters and the competitive effects of aluminum

Chemical Geology
By: , and 



The effect of simultaneous competitive speciation of dissolved rare earth elements (REEs) in acidic waters (pH 3.3 to 5.2) has been evaluated by applying the PHREEQE code to the speciation of water analyses from Spain, Brazil, USA, and Canada. The main ions that might affect REE are Al3+, F-, SO42-, and PO43-. Fluoride, normally a significant complexer of REEs, is strongly associated with Al3+ in acid waters and consequently has little influence on REEs. The inclusion of aluminum concentrations in speciation calculations for acidic waters is essential for reliable speciation of REEs. Phosphate concentrations are too low (10-4 to 10-7 m) to affect REE speciation. Consequently, SO42- is the only important complexing ligand for REEs under these conditions. According to Millero [Millero, F.J., 1992. Stability constants for the formation of rare earth inorganic complexes as a function of ionic strength. Geochim. Cosmochim. Acta, 56, 3123-3132], the lanthanide sulfate stability constants are nearly constant with increasing atomic number so that no REE fractionation would be anticipated from aqueous complexation in acidic waters. Hence, REE enrichments or depletions must arise from mass transfer reactions. 

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title REE speciation in low-temperature acidic waters and the competitive effects of aluminum
Series title Chemical Geology
DOI 10.1016/S0009-2541(99)00166-7
Volume 165
Issue 3-4
Year Published 2000
Language English
Publisher Elsevier
Contributing office(s) Toxic Substances Hydrology Program
Description 14 p.
First page 167
Last page 180
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