Selective Immobilization of Highly Valent Radionuclides by Carboxyl Functionalized Mesoporous Silica Microspheres: Batch, XPS, and EXAFS Analyses

Abstract

The removal of radionuclides on natural inorganic materials is a pursuing issue for many nuclear-related processes requiring remediation of radioactive wastewater. However, the current natural adsorbents with low cost and great biocompatibility suffer from limitations in removal efficiency, regeneration capability, or/and operation conditions. Herein, silicon dioxide (SiO2) as the major ingredient of clay minerals was modified by carboxyl groups to improve its adsorption affinity for highly valent radionuclides. The batch experiments for U­(VI) capture showed that the carboxyl-modified mesoporous silica (SiO2-COOH) microspheres had fast sorption velocity and were exceptionally capable in efficiently sequestering U­(VI) under various relevant interferences. The resulting SiO2-COOH possessed great potential for controlled loading of highly valent radionuclides in a selective adsorption order of U­(VI) > Th­(IV) > trivalent ions > divalent ions > Cs­(I). The XPS and EXAFS analyses further confirmed that the interaction mechanism between SiO2-COOH and U­(VI) was mainly attributed to the inner-sphere complexation with one or two oxygen atoms shared between the UO2 2+ and the carboxyl ligand. Carboxyl group modification of natural inorganic materials provides a general and powerful approach to eliminate highly valent radionuclides in various wastewater systems.

Removal of Mercury (II) by EDTA-Functionalized Magnetic CoFe2O4@SiO2 Nanomaterial with Core-Shell Structure

“…Figure 7f shows a high-resolution scan of O 1 s , which contains four different binding energy values: 532.4 and 531.9 eV correspond to carbon-based O–C=O and Si–O/C–O [42], respectively, whereas 531.3 eV corresponds to the surface hydroxyl group O–H, and 530.4 eV corresponds to Co–O/Fe–O [40,43]. In the C 1s scan of Figure 7g, the four different binding energy values observed at 283.5, 284.2, 285.2 and 287.5 eV correspond to C in C–Si, C–H, C–C/C–N and O–C=O, respectively.…”

The Study of Amidoxime-Functionalized Cellulose Separate Th(IV) from Aqueous Solution

“…The electron excitation of the O element requires X-rays with higher energy, so the binding energy of O 1s in the spectrum becomes higher [ 34 ]. The peak area increases, which can be explained by the coordination between C-O and radionuclides during adsorption [ 35 ]. It can be observed from Figure 1 Th 4f that peaks belonging to Th 4f 7/2 and Th 4f 5/2 orbits appear at 333.1 eV and 342.4 eV, which indicates that thorium ions already exist on the surface of the adsorbent.…”

Ratiometric Fluorescent Biosensor Based on Forster Resonance Energy Transfer between Carbon Dots and Acridine Orange for miRNA Analysis

“…In addition to Si–O and −OH, the absorption bands attributed to C–H and −COOH appeared in the FTIR spectrum of COOH-SiO 2 , indicating that the carboxyl was successfully modified on SiO 2 ( Figure 1 f). 31 …”

“…As shown in Figure S3, the monodispersed COOH-SiO 2 exhibited an average size of about 300 nm. In addition to Si–O and −OH, the absorption bands attributed to C–H and −COOH appeared in the FTIR spectrum of COOH-SiO 2 , indicating that the carboxyl was successfully modified on SiO 2 (Figure f) …”