Synthesis of a novel environmental-friendly biocarbon composite and its highly efficient removal of uranium(VI) and thorium(IV) from aqueous solution

The development and utilization of nuclear energy produced a large amount of uranium(VI)/thorium(IV)-containing wastewater, which would be harmful to the environment. The enrichment of the radioactive ions from wastewater using a green and environmentally friendly technology was great important to the protection of water environment and the resource utilization of energy materials. In this work, a novel cow manure-derived biocarbon-based composite was prepared by impregnation-carbonization technology for the separation of thorium(IV) and uranium(VI) from water. The composite could efficiently separate the target ions under acidic condition (pH = 4.5) with high saturated separation capacities (675.1 mg/g for uranium(VI) and 710.4 mg/g for thorium(IV)), high removal percentages (97.5% for uranium(VI) and 99.8% for thorium(IV)), fast separation rates in the initial stage of separation process (10.3 mg/(g·min) for thorium(IV) and 4.6 mg/(g·min) for uranium(VI) and good reusability after five cycles. Even in 1.0 g/L of NaCl solution, the removal efficiencies still exceeded 88.4% for uranium(VI) and 93.1% for thorium(IV). These results exposed the perfect performance of the cow manure-derived biochar-based composite in thorium(IV) and uranium(VI) separation. Moreover, various models were used to fit the experimental data, which revealed that the uranium(VI)/thorium(IV) separation on the biocarbon composite was monolayer chemical adsorption and the complexation was mainly the way for capturing uranium(VI) and thorium(IV). This work might offer a new perspective for the resource management of animal manure and a prospect for the practical application of biochar in thorium(IV) and uranium(VI) recovery.