Kinetics of the complexation of dioxouranium(VI) with selected diphosphonic acids in acidic solutions

Journal Article · Wed Apr 28 04:00:00 EDT 1993 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00061a045· OSTI ID:6233845

Hines, M A; Sullivan, J C; Nash, K L ^[1]

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1. Argonne National Lab., IL (United States)

The kinetics of reactions of dioxouranium(VI) with diphosphonic acid complexants (methanediphosphonic acid (MDPA), 1-hydroxyethane-1,1-diphosphonic acid (HEDPA), and ethane-1,2-diphosphonic acid (E12DPA)) have been investigated in acidic solutions (pH 1-2) by stopped-flow spectrophotometry where arsenazo III is used as an indicator for the free uranyl ion. The complex formation reaction was acid independent at acidities above 0.03 M while the dissociation reaction had a direct dependence on the acidity over the range of hydrogen ion concentration 0.1-0.01 M. The measured first-order rate parameter is defined as k[sub obs] = k[sub f][UO[sub 2][sup 2+]][H[sub 3]L] + k[sub d][UO[sub 2]H[sub 2]L][H[sup +]]. The rate parameters for formation and dissociation reactions at 25.0[degrees]C are as follows. Uranyl-MDPA: k[sub f] = 6813 ([+-]320) M[sup [minus]1] s[sup [minus]1], k[sub d] = 31.3 ([+-]2.1) s[sup [minus]1]. Uranyl-HEDPA: k[sub f] = 7715 ([+-]146) M[sup [minus]1] s[sup [minus]1], k[sub d] = 27.5 ([+-]2.0) s[sup [minus]1]. Uranyl-E12DPA: k[sub f] = 216 ([+-]24) M[sup [minus]1] s[sup [minus]1], k[sub d] = 47.4 ([+-]2.6) s[sup [minus]1]. The equilibrium quotient calculated from the rate parameters for the formation of uranyl-E12DPA is in agreement with the previously reported stability constant for that complex. Activation parameters for both formation and dissociation reactions are consistent with an associative mechanism. 15 refs., 6 figs., 1 tab.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6233845
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 32:9; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702* -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
ABSORPTION SPECTROSCOPY
ACTINIDE COMPLEXES
ACTIVATION ENERGY
AQUEOUS SOLUTIONS
AROMATICS
ARSENAZO
ARSONIC ACIDS
AZO COMPOUNDS
CHEMICAL REACTION KINETICS
COMPLEXES
DISPERSIONS
DISSOCIATION
ELEMENTS
ENERGY
EQUILIBRIUM
HYDROGEN
HYDROXY COMPOUNDS
KINETICS
MIXTURES
NONMETALS
ORGANIC ACIDS
ORGANIC ARSENIC COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PH VALUE
PHENOLS
PHOSPHONIC ACIDS
POLYPHENOLS
REACTION KINETICS
REAGENTS
SOLUTIONS
SPECTROSCOPY
STABILITY
SULFONIC ACIDS
URANIUM COMPLEXES
URANYL COMPLEXES