January 6, 2020 Dataset Open Access

Lösch, Henry; Raiwa, Manuel; Jordan, Norbert; Steppert, Michael; Steudtner, Robin; Stumpf, Thorsten; Huittinen, Nina Maria

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{
  "abstract": "<p>In this study the complexation of U(VI) with orthosilicic acid (H<sub>4</sub>SiO<sub>4</sub>) between pH 3.5 and 5 with electrospray ionization mass spectrometry (ESI\u2012MS) and laser\u2012induced luminescence spectroscopy was comprehensively characterized. The ESI\u2012MS experiments performed at a total silicon concentration of 5\u221910<sup>\u20125</sup> M (exceeding the solubility of amorphous silica at both pH\u2012values) revealed the formation of oligomeric sodium\u2012silicates in addition to the UO<sub>2</sub>OSi(OH)<sub>3</sub><sup>+</sup> species. For the luminescence spectroscopic experiments (25 &deg;C), the U(VI) concentration was fixed at 5\u221910<sup>\u20126</sup> M, the silicon concentration was varied between 1.3\u221910<sup>\u20124</sup> \u2012 1.3\u221910<sup>\u20123</sup> M (reducing the formation of silicon oligomers) and the ionic strength was kept constant at 0.2 M NaClO<sub>4</sub>. The results confirmed the formation of the aqueous UO<sub>2</sub>OSi(OH)<sub>3</sub><sup>+</sup> complex. The conditional complexation constant at 25 &deg;C, log *&beta; = \u20120.31&plusmn; 0.24, was extrapolated to infinite dilution using the Davies equation, which led to log *&beta;<sup>0</sup> = \u20120.06 &plusmn; 0.24. Further experiments at different temperatures (1 &ndash; 25 &deg;C) allowed the calculation of the molal enthalpy of reaction &Delta;<sub>r</sub>H<sub>m</sub><sup>0</sup> = 45.8 &plusmn; 22.5 kJ\u2219mol\u20121 and molal entropy of reaction &Delta;<sub>r</sub>S<sub>m</sub><sup>0</sup> = 152.5 &plusmn; 78.8 J\u2219K\u20121\u2219mol\u20121 using the van&rsquo;t Hoff equation, corroborating an endothermic and entropy driven complexation process.</p>", 
  "id": "211", 
  "type": "dataset", 
  "title": "Temperature\u2012dependent luminescence spectroscopic and mass spectrometric investigations of U(VI) complexation with aqueous silicates in the acidic pH\u2012range", 
  "DOI": "10.14278/rodare.211", 
  "language": "eng", 
  "version": "Version_1_2020-01-06", 
  "publisher": "Rodare", 
  "issued": {
    "date-parts": [
      [
        2020, 
        1, 
        6
      ]
    ]
  }, 
  "author": [
    {
      "family": "L\u00f6sch, Henry"
    }, 
    {
      "family": "Raiwa, Manuel"
    }, 
    {
      "family": "Jordan, Norbert"
    }, 
    {
      "family": "Steppert, Michael"
    }, 
    {
      "family": "Steudtner, Robin"
    }, 
    {
      "family": "Stumpf, Thorsten"
    }, 
    {
      "family": "Huittinen, Nina Maria"
    }
  ]
}