Direct spectroscopic speciation of the complexation of U(VI) in acetate solution

Abstract

As a result of systematic UV–Vis absorption spectroscopy studies in the U(VI) acetate system, the single component spectrum of [UO2CH3COO]+ with characteristic parameters was evaluated and applied in quantitative deconvolution of multicomponent spectra. Free acetate concentrations were obtained by the use of geochemical and probabilistic modelling codes. A total of 51 UV–Vis spectra were collected in a wide range of experimental conditions where coordination of U(VI) by acetate ion was indicated by characteristic variations in the spectra structure as compared to UO22+. Using chemometric data analysis, the resulting factor structure was evaluated to obtain a subset of 14 spectra holding only one coordinated species next to UO22+(aq). The molar absorption coefficient for the U(VI) monoaceto species was estimated as ε418 = 17.8 ± 1 dm3 mol−1 cm−1. Spectral deconvolution was used to obtain an estimate of the species concentrations which allowed to calculate for each sample the free acetate concentration, the total U(VI) amount and, eventually, to estimate the formation quotient lg β11 = 2.8 ± 0.3 of UO2(CH3COO)+.Graphical Abstract

Determination of the Stability Constants of the Acetate Complexes of the Actinides Am(III), Th(IV), Np(V), and U(VI) Using Capillary Electrophoresis-Inductively Coupled Plasma Mass Spectrometry

“…The first works were carried out by Ahrland et al. , who determined stability constants of three U­(VI)–acetate complexes in sodium perchlorate solution using a potentiometric method. Subsequent studies by different groups on both stability constants and structural aspects are summarized in the literature. − Most recently the stability constant for the 1:1 acetate/U­(VI) complex was determined by Meinrath et al by means of UV–vis spectroscopy. The majority of the works mentioned identified three successive complexes (1:1, 1:2, and 1:3) with a bidentate binding of the acetate ligand.…”

Complex formation between UO22+and α-isosaccharinic acid: insights on a molecular level

“…The averaged single component spectra of all components are shown in Fig. SI 32 ( 50,51 Therefore, these results suggest the formation of four dominant UO 2 2+ -ISA complexes. The spectral similarities of components 3 and 5 may be an indication for structural similarities of these species.…”