Radionuclide tolerance mechanism of plants for ultraselective enrichment of low content of thorium with exceptional selectivity coefficient

Abstract Selective enriching low content of radionuclides from radioactive wastewater is a critical issue for environmentally benign utilization of nuclear power. Inspired by the tolerance mechanism of plants to radionuclides, we developed a pH-triggered ultraselective coordinative adsorption (CA) membrane. The as-prepared CA membrane featured the advantages of both coordinative adsorption and membrane separation, including ultrahigh selectivity coefficient of 1242, large capacity (80 L m -2 ) and short mass transfer distance. The adsorption isotherms of Th 4+ on the CA membrane were well described by the Freundlich model (R 2 > 0.99), and the adsorption kinetics have a good fitting by using the pseudo-second-order kinetic model (R 2 > 0.99). In a continuous separation under gravity, the CA membrane was able to selectively enrich the low content of Th 4+ (0.05 mmol L -1 ) in the presence of 700 folds (35 mmol L -1 ) of co-existing ions (Na + , Mg 2+ , K + , Ca 2+ , Sr 2+ , Cs + and Ba 2+ ). The exceptional extraction efficiency to Th 4+ was 100%, superior to that (3.7%) of all co-existing ions. Notably, the Th 4+ enriched on the CA membrane was facilely eluted by diluted HNO 3 (0.1 mol L -1 ). The Th 4+ in the eluents was enriched by up to 54 folds. The eluted CA membrane was further reused for selective enrichment of Th 4+ , which showed no obvious loss of selectivity and enrichment capability. Our strategy might open up a new strategy for realizing ultraselective and recyclable enrichment of low content of irradiation contaminants from wastewater.