Phosphine-functionalized aluminum-based metal organic framework for ultra-fast and selective thorium capture from rare earth contaminated wastewater

Thorium, a radioactive nuclide, commonly accompanies rare earth minerals. The wastewater generated during the mining and processing of these ores poses significant risks to the environment and public health. Therefore, efficient adsorbents for removing thorium are crucial in the recent research. This study synthesized a novel dimethylphosphine functionalized Al-based metal organic framework (CAU-PMIDA) and evaluated its adsorption selectivity for thorium in wastewater. Adsorption mechanism studies have shown that CAU-PMIDA adsorbs thorium mainly through chemical adsorption，and dynamics follow a pseudo second-order model and reach equilibrium within approximately 30 min. Thorium adsorption on CAU-PMIDA fits the Langmuir isotherm, achieving a maximum capacity of 199.50 mg/g at pH 3.5. Coexisting rare earth ions have minimal interference, demonstrating remarkable Th(IV) selectivity. CAU-PMIDA maintains excellent regeneration performance，high adsorption capacity and selectivity under acidic conditions, which indicating significant potential in the treatment especially from acidic rare earth contaminated wastewater. Selective thorium adsorption using CAU-PMIDA from rare earth contaminated wastewater. • Phosphine-functionalized Al-MOF synthesized via modification with PMIDA is used for selective capture of Th (IV) from rare earth containated wastewater. • It shows a remarkable adsorption capacity (Q max =199.50 mg/g) for Th(IV) in acid aqueous solution, which is significantly higher than that of the unmodified CAU-1 (85.04 mg/g). • It exhibits remarkable selectivity for Th(IV), in the condition of many other coexisting rare earth metal ions. • The isothermal adsorption data of thorium fits well with the Langmuir mode.