One particle three targets: Phosphate anion-modified magnetic mesoporous silica with enhanced fluorescence for sensitive detection, efficient adsorption, and repeated removal of uranium (VI) ions

An ideal adsorbent material that combines the multiple capabilities of sensitive detection, efficient adsorption, and repeatable removal of uranium (U) from the environment remains a serious challenge. Herin, a general method was developed for synthesizing a series of phosphate anions (such as: PO43-, P2O74-, P3O105- and P6O186-) modified magnetic mesoporous silica nanoparticles (Fe3O4 @mSiO2-Zn2+ NPs). The mesoporous surfaces and abundant phosphate groups provide potential, powerful uranium-binding sites for capturing U(VI) ions. Especially, the optimum adsorption capacity of Fe3O4 @mSiO2-Zn2+/P3O105- NPs was as high as 885.90 mg·g-1 (298 K), which was higher than that of unmodified or other phosphate anions-modified Fe3O4 @mSiO2-Zn2+ NPs. Meanwhile, P3O105--binding sites and mesoporous surfaces also strongly restrict U(VI) ions' fluorescence vibrational inactivation, the adsorption results in rapid green fluorescence enhancement (within 180 s), and an ultra-low detection limit (4.5 nmol·L-1), which is well below the standard in drinking water of the World Health Organization (WHO). Furthermore, even after 5 cycles, the adsorbent still maintained their original adsorption capacity of 80.21% and displayed excellent selectivity for detecting and removing U(VI) from seawater. Based on these results, the Fe3O4 @mSiO2-Zn2+/P3O105- NPs seem to be a suitable multifunctional adsorbent for the detection, adsorption, and removal of U(VI) from environment.