Equilibrium studies and redox kinetics of the peroxo complex of zirconium(IV) in acidic perchlorate solution

Technical Report · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5905569

Thompson, R C

The complexation of zirconium (IV) by hydrogen peroxide was studied in aqueous solutions containing M Zr(IV), M H/sub 2/0/sub 2/, and M HClO/sub 4/. The peroxozirconium(IV) complex does not exhibit detectable absorption bands in the visible- or ultraviolet-wavelength regions. Therefore, the equilibrium concentrations of uncomplexed Zr/sup 4 +/ and H/sub 2/O/sub 2/ were measured by the use of the indicators 2-thenoyltrifluoroacetone and titanium(IV), respectively. The principal complex formed is a tetrameric species (4:2) containing four Zr(IV) and two peroxide ions. The value of the formation constant is given. The thermodynamic parameters ..delta..H/sub f//sup 0/ = 11.2 kcal/mol and ..delta..S/sub f//sup 0/ = 130 cal/(deg mol) were calculated from the temperature dependence of K4:2 in 1.96 M HClO4. The variation of the formation constant with acidity at an ionic stength of 2.0 M allows the tentative formulation of the peroxozirconium(IV) complex as Zr/sub 4/(O/sub 2/2(OH)4(8+). The results of concentration-jump kinetic experiments were interpreted. Kinetic studies of the oxidation of peroxozirconium(IV) by cerium(IV) and the reduction by sulfur(IV) in 1.96 M HClO4 yielded a common rate expression. According to the authors interpretation, both systems proceed by a rate-determining ring-opening process on peroxozirconium(IV), followed by rapid attack on an exposed pendant -O/sub 2/H unit by the external reagent.

• Research Organization: Missouri Univ., Columbia (USA). Dept. of Chemistry
• OSTI ID: 5905569
• Report Number(s): AD-A-164030/9/XAB
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
CHARGED PARTICLES
CHEMICAL REACTIONS
COMPLEXES
ELEMENTS
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
INORGANIC ACIDS
IONS
KINETICS
METALS
OXIDATION
OXYGEN COMPOUNDS
PERCHLORIC ACID
PEROXIDES
REACTION KINETICS
REDOX REACTIONS
SPECTRA
THERMODYNAMICS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS
WATER
ZIRCONIUM
ZIRCONIUM COMPLEXES