International Journal for chemical aspects of nuclear science and technology
Editor-in-Chief: Qaim, Syed M.
IMPACT FACTOR 2018: 1.339
CiteScore 2018: 1.20
SCImago Journal Rank (SJR) 2018: 0.333
Source Normalized Impact per Paper (SNIP) 2018: 0.720
Influence of pH and metal ion loading on the Cm(III) humate complexation: a time resolved laser fluorescence spectroscopy study
Interaction of trivalent lanthanides and Cm(III) with humic acid (HA) (10 mg/L) is studied as a function of metal ion concentration (1×10-8 to 5×10-5 mol/L) and pH (2.5 to 7.0) in 0.01 mol/L NaClO4. Time resolved laser fluorescence spectroscopy (TRLFS) reveals a slight blue-shift/broadening of the fluorescence peak position for the Cm(III)-HA complex combined with an enhanced contribution of a short-lived fluorescence component with increasing metal ion loading and decreasing pH. Fluorescence decay for Cm(III)-HA is non-monoexponential under all investigated conditions and lifetimes can be described by assuming a short lived (τ=61 μs) and a longer lived contribution (τ=142 μs). These findings are explained by the existence of a certain heterogeneity in binding sites inducing slightly variable ligand-field splitting in the Cm(III)-HA complex. Batch experiments with a Eu(III)-HA solution contacted with a chelating resin reveal a decrease of the solid/liquid distribution coefficient by decreasing the occupancy of HA ligand sites from 4% to 0.2%. This observation indicates that complexation constants for the Eu(III)-HA complex vary with metal loading. Differences in related constants are, however, smaller than one order of magnitude. Variations in fluorescence lifetimes are interpreted as a consequence of increasing HA agglomeration at increasing metal loading and decreasing pH, thus leading to an enhanced local density of chromophoric groups close to the Cm(III) ion favouring non-radiative energy transition. HA agglomeration at low pH and increasing metal ion loading is well known from previous studies using flow-field flow fractionation (FFF) coupled to ICP-mass spectrometry and UV-Vis spectrophotometry. Our experimental results demonstrate the dynamic properties of metal-HA complexes depending on chemical conditions.
Here you can find all Crossref-listed publications in which this article is cited. If you would like to receive automatic email messages as soon as this article is cited in other publications, simply activate the “Citation Alert” on the top of this page.