Selective Extraction of Thorium from Rare Earth Elements Using Wrinkled Mesoporous Carbon

Liquid fluoride thorium reactors have been considered as replacements for uranium-based nuclear reactors, having many economic and environmental advantages. The production of thorium is usually accompanied by the separation of thorium from rare earth elements since the major thorium production mineral, monazite, contains other rare earth elements. The conventional manufacturing process involves a liquid-liquid extraction with organic ligands. There is a need to develop solid state absorbents with good reusability for metal ion separation processes. Porous carbon is particularly interesting due to acid/base resistance. A new absorbent, surface-oxidized wrinkled mesoporous carbon (WMC-O), has been prepared for the selective extraction of thorium ions from rare earth ions. WMC-O shows high selectivity for thorium adsorption due to the 4+ oxidation state of thorium. The distribution coefficient ( K_d) of the WMC-O for thorium from all rare earth elements is 2 orders of magnitude larger than that of surface-oxidized activated carbon (13 × 10⁴ vs 35 × 10² at pH 2.15). WMC-O also shows a high adsorption capacity for pure rare earth ions ( K_d > 3 × 10⁵). These features make WMC-O a promising absorbent for thorium extraction and rare earth ion recovery.