Hydroxyl-glutarimidedioxime: a complexing reagent to strip uranium from the organic phase of P350

Abstract

The extractant di(1-methyl-heptyl) methylphosphonate (P350) shows excellent performance in the separation of thorium and uranium; however, it poses a significant challenge for the efficient stripping of uranium(VI) from the organic phase. To address this, a hydroxyl-functionalized ligand, hydroxyl-glutarimidedioxime (H₂B), was designed and synthesized by introducing a hydroxyl group onto the piperidine ring of the parent ligand glutarimidedioxime (H₂A). This structural modification markedly enhanced the aqueous solubility of H₂B without altering its tridentate coordination mode with uranyl. Stripping experiments confirmed that H₂B enables near-quantitative recovery of uranium (∼100%), significantly outperforming both H₂A and conventional alkaline stripping agents. Computational and thermodynamic studies revealed that while H₂B exhibits a slightly lower binding strength to uranyl than H₂A, it maintains a strong affinity and an identical coordination geometry. These findings underscore that enhancing ligand solubility through subtle molecular design is a critical strategy for optimizing uranyl separation efficiency, providing a valuable new direction for ligand development in thorium fuel cycle reprocessing.