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

Journal Article
ract, vol. 98, iss. 9-11, pp. 737-742, 2010
Authors
J. M. Schwantes, Peter H. Santschi
Abstract
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+, logߙK = −2.1(−10)  (1) ≡SOH + Pu4+ ↔ ≡SOPu3+ + H+, logߙK = 15.3(7.2)  (2) ≡SOH + PuO2 + ↔ ≡SOPuO2 + H+, logߙK = −8.5(−16.5)  (3) ≡SOH + PuO2 2+ ↔ ≡SOPuO2 + + H+, logߙK = 1.2(−6.5)  (4) ≡SOH + Pu4+ + 3H2O ↔ ≡SOPu(OH)3 + 4H+, logߙK = 12.5(4.6)  (5) ≡SOH + Pu4+ + 4H2O ↔ ≡SOPu(OH)4 + 5H+, logߙK = 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:...
English