Mechanisms of plutonium sorption to mineral oxide surfaces: new insights with implications for colloid-enhanced migration

J. M. Schwantes, P. H. Santschi

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

New equilibrium and kinetic models have been developed to describe rate-limited sorption and desorption of Pu onto and off of mineral oxide surfaces using a generic approach to estimate sorption constants that require minimal laboratory calibrations. Equilibrium reactions describing a total of six surface species were derived from a combination of empirical relationships previously described in the literature and generated as part of this work. These sorption reactions and corresponding equilibrium constants onto goethite (and silica) are: ≡SOH+Pu3+↔≡SOPu2++H+ , log K =-2.1(-10) (1) ≡SOH+Pu4+↔≡SOPu3++H+ , log K = 15.3(7.2) (2) ≡SOH+PuO2+↔≡SOPuO 2+H+ , log K =-8.5(-16.5) (3) ≡SOH+PuO2 2+↔≡SOPuO2++H+ , log K = 1.2(-6.5) (4) ≡SOH+Pu4++3H2O↔≡SOPu(OH)3+4H+ , log K = 12.5(4.6) (5) ≡SOH+Pu4++4H2O↔≡ SOPu(OH)4-+5H+ , log K = 5.0(-2.3) (6) The kinetic model decouples reduced (III, IV) and oxidized (V, VI) forms of Pu via a single rate-limiting, but reversible, surface mediated reaction: ≡SOPuO2+H 2O+1/2H2(g) k1↔ k2 ≡SOPu(OH)2 log k1 =-5.3 (7) Where the reaction rate is equal to: d[≡SOPu 2] dt = k1[Puox]-k2[Pured] (8) and [Pu ox] and [Pured] are the sums of the oxidized (V and VI) and reduced (III and IV) surface species, respectively.

Original languageEnglish (US)
Pages (from-to)737-742
Number of pages6
JournalRadiochimica Acta
Volume98
Issue number9-11
DOIs
StatePublished - 2010

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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