A novel strategy for sequential separation of Th(IV) from highly acidic wastewater based on solid phase extraction

The potential applications and advantages of thorium(Th) in the development of the nuclear industry make the effective separation of Th(IV) crucial for depleted fuel management and environmental safety. However, selectively capturing of Th(IV) from high-concentration nitric acid remains a challenging task. In this work, a novel solid-phase extraction resin (TOPO/XAD-7) was successfully synthesized by vacuum impregnation of trioctylphosphine oxide (TOPO) into an acrylic-based polymer (XAD-7 resin). It exhibited excellent adsorption abilities for Th(IV), including wide highly concentration acid tolerance (0.01-6 mol L-1 HNO3), high adsorption capacity of 59.79 mg g(-1), fast adsorption kinetic (< 60 min) and super elevated selectivity. The adsorption mechanism of the resin involves neutral chelation extraction, with the P=O group being the main adsorption binding site. Additionally, the resin was demonstrated good reusability and stability under extreme conditions (high acidity, high temperature and high radiation). Furthermore, dynamic column experiments conducted using an automated separation system validated the practical application of TOPO/XAD-7 resin for the separation of Th (IV) and U(VI)/Th(IV) in wastewater, achieving high element recovery (> 99.5%) and a high U(VI) decontamination factor (3.5 x 10(5)). This work confirms the excellent potential of TOPO/XAD-7 resin for the separation and enrichment of Th(IV) in nuclear wastewater.