Microwave-assisted preparation of Mn3O4@sepiolite nanocomposite for highly efficient removal of uranium

Abstract

Nuclear energy is an important alternative energy source to non-renewable fossil fuels. Nevertheless, the nuclear contamination associated with nuclear activities and wastes is a formidable concern worldwide. Uranium is one of the most commonly used and discharged radionuclides, and hexavalent uranium [U(VI)] has significant mobility owing to its good solubility in water, leading to serious environmental and health risks. However, facile and economical solutions to effectively treating U(VI)-contaminated water are still limited. Herein, Mn3O4 nanoparticles were dispersedly anchored on sepiolite nanofibers via a facile microwave-assisted method for adsorbing U(VI) from aqueous solutions. Batch adsorption experiments showed that the nanocomposite possessed faster removal kinetics and greater removal capacity than the individual sepiolite and Mn3O4, as well as better removal performance than many reported inorganic and organic adsorbents. The nanocomposite can also reduce the U(VI) concentrations to far less than the standard of drinking water. Furthermore, a systematic investigation of the adsorption mechanism revealed that the nanocomponents Mn3O4 and sepiolite were responsible for the high-affinity U(VI) capture through the bonding of ≡Mn–O–U(VI) and ≡Si/Mg–O–U(VI), respectively, but the loaded Mn3O4 nanoparticles dominated the adsorption. Given that the simple synthesis and excellent U(VI) removal performance, the Mn3O4@sepiolite nanocomposite holds great promise for practical applications in radioactive uranium treatment.