The aqueous geochemistry of the rare-earth elements and yttrium

摘要: Abstract Literature data on the nature and thermodynamics of inorganic complex species REE Y have been critically reviewed. Theoretical considerations suggest that trivalent should exhibit strong, predominantly electrostatic complexing with “hard” ligands such as fluoride, sulfate, phosphate, carbonate hydroxide this is borne out by available experimental data. Complexing these metals chloride nitrate moderately weak ammonia bisulfide extremely to nonexistent. A considerable amount concordant thermodynamic are at 25°C for sulfate complexes LnSO + 4 Ln(SO ) − 2 , fluoride LnF 2+ 0 3 LnNO LnCl where Ln signifies or Y. There much fewer reliable hydroxide, phosphate in fact, exact stoichiometries still somewhat uncertain. However, it appears LnOH LnCO Ln(CO LnHCO LnH PO identified. Calculation speciation Eu ( β = 10 −7 m) a typical groundwater SO 2− −4 m, C 2·10 F −6 CO NO m 3− shows simple ion most important acidic pH become predominant near-neutral basic pH. Even relatively saline waters, do not account significant fraction solution completely negligible surface waters groundwaters. Nitrate also even environments concentration ligand artificially high due pollution. Phosphate can attain importance concentrations anomalous (i.e. 2–4 orders magnitude higher than model groundwater) either natural anthropogenic factors. Data stabilities low temperature critical those concerned safe nuclear waste disposal, geochemical exploration deposits, use tracers seawater fresh water. The information needed present time includes: (1) hydrolysis constants; (2) additional complexes; (3) mixed (4) more complete complexation behavior +4 +2 oxidation states REE.