Publications by authors named "Madlen Stockmann"

3 Publications

  • Page 1 of 1

Effect of DTPA on europium sorption onto quartz - Batch sorption experiments and surface complexation modeling.

Chemosphere 2020 Jan 5;239:124771. Epub 2019 Sep 5.

Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Reactive Transport Department, Permoserstr. 15, 04318, Leipzig, Germany.

Sorption of radionuclides on mineral surfaces retards their migration in the environment of a repository. Presence of organic ligands, however, affects sorption and consequently influences their transport behavior. In this study, we quantify the sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of diethylenetriaminepentaacetic acid (DTPA). Batch sorption experiments show a pH-dependent sorption of Eu(III) on quartz. The presence of DTPA results in slightly higher sorption of Eu(III) at neutral to slightly acidic pH and considerably lower sorption at alkaline conditions. Sorption experiments were simulated using the Diffuse Double Layer Model (DDLM) with single sorption sites (≡QOH) and monodentate surface complexation. The reactions were established based on the aqueous speciation calculation under the experimental conditions, and the thermodynamic constants of surface reactions were obtained and refined by numerical optimization. Results of surface complexation modeling show the formation of a surface species ≡QOHEuDTPA, explaining the elevated sorption of Eu(III) at neutral to slightly acidic pH. In contrast, dissolved EuDTPA complex species are present at alkaline pH, resulting in an enhanced mobility of Eu(III).
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http://dx.doi.org/10.1016/j.chemosphere.2019.124771DOI Listing
January 2020

Effect of glutamic acid on copper sorption onto kaolinite - Batch experiments and surface complexation modeling.

Chemosphere 2017 Jul 21;178:277-281. Epub 2017 Mar 21.

Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Permoserstr. 15, 04318 Leipzig, Germany. Electronic address:

High carbonate content of the European Kupferschiefer ore deposits is a challenge for acid copper leaching (pH ≤ 2). Therefore investigating the mobility behavior of Cu(II) under conditions related to an alternative, neutrophil biohydrometallurgical Cu(II) leaching approach is of interest. As glutamic acid (Glu) might be present as a component in the growth media, we studied its effects on the adsorption of Cu(II) onto kaolinite. The binary and ternary batch sorption measurements of Cu(II) and Glu onto kaolinite were performed in the presence of 10 mM NaClO as background electrolyte and at a pH range from 4 to 9. Sorption experiments were modeled by the charge-distribution multi-site ion complexation (CD-MUSIC) model by using single sorption site (≡SOH) and monodentate surface complexation reactions. Glu sorption on kaolinite is weak (<10%) and independent of pH. Furthermore, Glu slightly enhances the Cu(II) sorption at low pH but strongly hinders (up to 50%) the sorption at higher pH and therewith enhances copper mobility. The results of isotherms show that Cu(II)-Glu sorption onto kaolinite mimics the Freundlich model. The proposed CD-MUSIC model provides a close fit to the experimental data and predicts the sorption of Cu(II), Cu(II)-Glu and Glu onto kaolinite as well as the effect of Glu on Cu(II) mobility.
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http://dx.doi.org/10.1016/j.chemosphere.2017.03.073DOI Listing
July 2017

The Sorption Processes of U(VI) onto SiO in the Presence of Phosphate: from Binary Surface Species to Precipitation.

Environ Sci Technol 2016 11 18;50(21):11610-11618. Epub 2016 Oct 18.

Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, D-01328 Dresden, Germany.

The ternary system containing aqueous U(VI), aqueous phosphate and solid SiO was comprehensively investigated using a batch sorption technique, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, time-resolved luminescence spectroscopy (TRLS), and surface complexation modeling (SCM). The batch sorption studies on silica gel (10 g/L) in the pH range 2.5 to 5 showed no significant increase in U(VI) uptake in the presence of phosphate at equimolar concentration of 20 μM, but significant increase in U(VI) uptake was observed for higher phosphate concentrations. In situ infrared and luminescence spectroscopic studies evidence the formation of two binary U(VI) surface species in the absence of phosphate, whereas after prolonged sorption in the presence of phosphate, the formation of a surface precipitate, most likely an autunite-like phase, is strongly suggested. From SCM, excellent fitting results were obtained exclusively considering two binary uranyl surface species and the formation of a solid uranyl phosphate phase. Ternary surface complexes were not needed to explain the data. The results of this study indicate that the sorption of U(VI) on SiO in the presence of inorganic phosphate initially involves binary surface-sorption species and evolves toward surface precipitation.
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http://dx.doi.org/10.1021/acs.est.6b02075DOI Listing
November 2016