Immobilizing amino-functionalized mesoporous silica into sodium alginate for efficiently removing low concentrations of uranium

A large volume of wastewater containing low concentrations of uranium is generated owing to the development and utilization of nuclear energy, which poses an environmental hazard. Therefore, an efficient strategy to remove uranium from the wastewater is important. In this study, a novel adsorbent, namely aMSP/SA, was prepared by immobilizing amino-functionalized mesoporous silica (aMSP) with sodium alginate (SA) for removing low concentration hexavalent U(VI), which is mobile and soluble. The effects of pH, initial concentration, time, temperature, coexisting ions, and regeneration on the removal efficiency of uranium by aMSP/SA were investigated. Results show that the saturated adsorption capacity of aMSP/SA for uranium was 210 mg/g at pH 4.0 and 313 K, and the concentration of U(VI) could be reduced from 1.0 mg/L to 1.31 μg/L. The aMSP/SA shows a high efficiency uranium removal of 99.41% in mine water and affinity toward uranium in a mixed metal solution. Additionally, the structure and possible adsorption mechanism of aMSP/SA were characterized by Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and energy-dispersive spectrometry (EDS). The main interaction mechanisms may be explained by ion exchange with Ca2+ on carboxyl and coordination with hydroxyl and amino groups. This study highlights that a high removal efficiency (99.87% for 1.0 mg/L) and easy separation of large particle sizes (3–4 mm) makes aMSP/SA a promising material for eliminating low concentration U(VI) in industrial applications. [Display omitted] •Applying aMSP/SA can reduce the concentration of U(VI) from 1.0 mg/L to 1.3 μg/L.•The removal efficiency of U(VI) from practical mine water by aMSP/SA is 99.41%.•The aMSP/SA shows selectivity toward uranium in a mixed metal solution.•The removal mechanisms are mainly related to ion-exchange and coordination.