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Title: Thermodynamic Features of Benzene-1,2-Diphosphonic Acid Complexes with Several Metal Ions

Among his many contributions to the advancement of f-element chemistry and separation science, Professor Gregory R. Choppin’s research group completed numerous investigations featuring the application of distribution techniques to the determination of metal complexation equilibrium quotients. Most of these studies focused on the chemistry of lanthanide and actinide complexes. In keeping with that tradition, this report discusses the complex formation equilibrium constants for complexes of trivalent europium (Eu3+) with benzene-1,2-diphosphonic acid (H4BzDP) determined using solvent extraction distribution experiments in 0.2 M (Na,H)ClO4 media in the temperature range of 5 – 45 degrees C. Protonation constants for HnBzDP4-n and stoichiometry and stability of BzDP4- complexes with Zn2+, Ni2+, and Cu2+ have also been determined using potentiometric titration (at I = 0.1 M) and 31P NMR spectroscopy. Heats of protonation of HnBzDPn-4 species have been determined by titration calorimetry. From the temperature dependence of the complex Eu3+-HnBzDPn-4 equilibrium constant, a composite enthalpy (?H = -15.1 (+/-1.0) kJ mol-1) of complexation has been computed. Comparing these thermodynamic parameters with literature reports on other diphosphonic acids and structurally similar carboxylic acids indicates that exothermic heats of complexation are unique to the Eu-BzDP system. Comparisons with thermodynamic data from the literature indicate that the fixedmore » geometry imposed by the benzene ring enhances complex stability.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0736--6299
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Solvent Extraction and Ion Exchange; Journal Volume: 31; Journal Issue: 4
Research Org:
Idaho National Laboratory (INL)
Sponsoring Org:
Country of Publication:
United States
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS diphosphonic acid complexant; Eu3+; HDEHP; Solvent Extraction; thermodynamics