The removal of uranium(VI) from laboratory and environmental waters using polyurea-cross-linked calcium alginate (X-alginate) aerogels has been investigated by means of batch-type experiments. The experimental data revealed that the material presents extremely high adsorption capacity for uranium(VI) (up to 2023 g kg −1 of aerogel). The adsorption process is endothermic, entropy-driven, and follows the Langmuir isotherm model. The Fourier transform infrared spectroscopy (FTIR) data corroborate the results of the batch experiments and indicate that adsorption occurs via the formation of inner-sphere complexes between the surface functional groups of Xalginate beads and UO 2
2+. The post-adsorption presence of uranium in the adsorbent was confirmed and quantified with energy-dispersive X-ray spectra (EDS) analysis. Compared to other aerogel adsorbents of UO 2 2+ from the literature, X-alginate aerogels show one of the highest sorption capacities per weight and the highest per volume. Uranium could be recovered almost quantitatively (∼100%) in aqueous solutions of Na 2 CO 3 (pH 11) or ethylenediaminetetraacetic acid (EDTA) (pH 10). The aerogel material has been effectively applied for the removal of uranium(VI) from acid mine drainage (AMD), groundwater, and seawater samples. It should be noted that X-alginate aerogel beads are stable in all of the above environments (i.e., no swelling, shrinking, or disintegration was observed). The extraordinary adsorption capacity, even in the presence of competing metal cations, and the stability of X-alginate aerogel beads in environmental waters render them excellent candidates for the specific application.
The removal of polyvalent metal ions Eu(III) and Th(IV) from aqueous solutions using polyurea-crosslinked calcium alginate (X-alginate) aerogels has been investigated by batch-type experiments under ambient conditions and pH 3. The material presents relatively high sorption capacity for Eu(III) (550 g kg−1) and Th(IV) (211 g kg−1). The lower sorption capacity for Th(IV) compared to Eu(III) is attributed to the net charge of the dominant species in solution under the given experimental conditions, which is Eu3+ for Eu(III), and Th(OH)22+ and Th(OH)3+ for Th(IV). Generally, the sorption is an endothermic and entropy-driven process, and it follows the Langmuir isotherm model. According to the FTIR spectra, sorption occurs via formation of inner-sphere complexes between the surface functional groups and the f-metal cationic species. The presence of europium and thorium in the adsorbent material was confirmed and quantified with EDS analysis. To the best of our knowledge, this is the first report of an aerogel material used as an adsorbent for Eu(III). Compared to other materials used for the sorption of the specific ions, which are mostly carbon-based, X-alginate aerogels show by far the highest sorption capacity. Regarding Th(IV) uptake, X-alginate aerogels show the highest capacity per volume (27.9 g L−1) among the aerogels reported in the literature. Both Eu(III) and Th(IV) could be recovered from the beads by 65% and 70%, respectively. Furthermore, Th(VI) could also be quantitatively removed from wastewater, while Eu(III) could be removed by 20%. The above, along with their stability in aqueous environments, make X-alginate aerogels attractive candidates for water treatment and metal recovery applications.
Two different silica conformations (xerogels and nanoparticles), both formed by the mediation of dendritic poly (ethylene imine), were tested at low pHs for problematic uranyl cation sorption. The effect of crucial factors, i.e., temperature, electrostatic forces, adsorbent composition, accessibility of the pollutant to the dendritic cavities, and MW of the organic matrix, was investigated to determine the optimum formulation for water purification under these conditions. This was attained with the aid of UV-visible and FTIR spectroscopy, dynamic light scattering (DLS), ζ-potential, liquid nitrogen (LN2) porosimetry, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results highlighted that both adsorbents have extraordinary sorption capacities. Xerogels are cost-effective since they approximate the performance of nanoparticles with much less organic content. Both adsorbents could be used in the form of dispersions. The xerogels, though, are more practicable materials since they may penetrate the pores of a metal or ceramic solid substrate in the form of a precursor gel-forming solution, producing composite purification devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.