Extraction of uranium with Hydrogen-Bonded Complex Extractants based on TBPO: chemical structure, performance and mechanism

Abstract

This study investigates the role of hydrogen bonding in Hydrogen-Bonded Complex Extractants (HBCEs) for uranium extraction from wastewater. Through integrated experimental and theoretical approaches including electrostatic potential (ESP) analysis, molecular binding energy calculations, Atoms in Molecules (AIM) theory, and spectroscopic characterization, we reveal how structural variations (carbon chain length, unsaturation degree, spatial configuration, and functional groups) modulate hydrogen bond characteristics. Results show that extending carbon chains enhances hydrogen bond strength (TBPO-18: -24.28 kcal/mol binding energy), while increasing unsaturation initially weakens then strengthens interactions. Linear structures exhibit superior hydrogen bonding versus cyclic configurations (TBPO-OH vs TBPO-HOH: 18.60 vs 14.47 kcal/mol). Extraction performance correlates with hydrogen bond stability, where TBPO-12 achieves maximum capacity (40.55 mg/L) due to optimal acid resistance. Mechanistic studies via ³¹P NMR titration confirm a two-step process: initial \({\text{UO}}_{2}^{2 + }\) complexation with TBPO’s P = O group, followed by hydrogen bond formation with HBDs. This work provides fundamental insights for rational design of high-efficiency HBCEs, highlighting hydrogen bond engineering as a key strategy for nuclear wastewater treatment.