Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste

Delegard, Calvin H.

doi:10.2172/1027695

Cited by 3 publications

(1 citation statement)

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“…Pu colloids, also sometimes referred to as Pu nanoparticles or Pu nanocolloids, 5 can be intrinsic Pu oxide/hydroxide particles as small as 2−5 nm in size 1,6,7 or particle aggregates ranging between 30 and 120 nm 7 , depending on the solution chemistry. Another form of Pu colloids, pseudo Pu colloids, arises when dissolved Pu or intrinsic Pu particles associate with colloidal particles that coexist in the system (e.g., natural groundwater colloids in the case of subsurface systems).…”

Section: ■ Introductionmentioning

confidence: 99%

Dispersion Stability and Electrokinetic Properties of Intrinsic Plutonium Colloids: Implications for Subsurface Transport

Abdel‐Fattah

Zhou

Boukhalfa

et al. 2013

Environ. Sci. Technol.

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Subsurface transport of plutonium (Pu) may be facilitated by the formation of intrinsic Pu colloids. While this colloid-facilitated transport is largely governed by the electrokinetic properties and dispersion stability (resistance to aggregation) of the colloids, reported experimental data is scarce. Here, we quantify the dependence of ζ-potential of intrinsic Pu(IV) colloids on pH and their aggregation rate on ionic strength. Results indicate an isoelectric point of pH 8.6 and a critical coagulation concentration of 0.1 M of 1:1 electrolyte at pH 11.4. The ζ-potential/pH dependence of the Pu(IV) colloids is similar to that of goethite and hematite colloids. Colloid interaction energy calculations using these values reveal an effective Hamaker constant of the intrinsic Pu(IV) colloids in water of 1.85 × 10(-19) J, corresponding to a relative permittivity of 6.21 and refractive index of 2.33, in agreement with first principles calculations. This relatively high Hamaker constant combined with the positive charge of Pu(IV) colloids under typical groundwater aquifer conditions led to two contradicting hypotheses: (a) the Pu(IV) colloids will exhibit significant aggregation and deposition, leading to a negligible subsurface transport or (b) the Pu(IV) colloids will associate with the relatively stable native groundwater colloids, leading to a considerable subsurface transport. Packed column transport experiments supported the second hypothesis.

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