Understanding the molecular-level behavior of f-element compounds in near-neutral and alkaline solutions is essential for developing a new alkaline based process for spent nuclear fuel reprocessing.  Traditionally, H₂O₂ has been used to alter the oxidation state of Pu and to precipitate both U and Pu from acidic solution by the formation of insoluble peroxide complexes.  In alkaline solutions, H₂O₂ forms surprisingly strong mixed peroxo-carbanato complexes with U, Np, and Pu with varying solubilities.  The addition of H₂O₂ can alter both the oxidation state and solution speciation of actinides in carbonate solutions.  Peroxide reacts with UO₂ (s) to form UO₂(O₂)(CO₃)₂^4- (aq), which is significantly more soluble than the previously thought solubility limiting species UO₂(CO₃)₃^4-.  While H₂O₂ oxidizes U(IV) to U(VI), it reduces Pu(VI) to Pu(IV).  Np shows the most complicated redox behavior, with Np(IV, V and VI) all stable in carbonate-peroxide media.  Np also appears to be a significant catalyst for the base-catalyzed decomposition of H₂O₂, while U and Pu only show mild catalytic activity.  At higher H₂O₂ concentrations, it is possible to precipitate Pu selectively from U as Na₈Pu₂(O₂)₂(CO₃)₆•12H₂O, and Np shows similar behavior forming multiple precipitates.  The significant changes in solubility of the peroxo species of Pu and Np relative to U allow for the possibility of an aqueous-based separations process as an alternative to the organic liquid-liquid extraction processes traditionally employed.  We will discuss the complex redox behavior of actinides (U, Np, and Pu) in carbonate-peroxide solutions, and how H₂O₂ can be used to control both the oxidation state and solubility of both Pu and Np in aqueous carbonate solutions.