The synthesis of a novel titanium oxide aerogel with highly enhanced removal of uranium and evaluation of the adsorption mechanism

Uranium Extraction from Seawater: A Novel Approach Using Aluminum Fumarate-Based Metal-Organic Framework Aerogels

Efficient extraction of uranyl ions from seawater is crucial for the commercialization of nuclear technology. Metal-organic frameworks (MOFs), with their superior uranium extraction properties, face challenges in large-scale applications due to their powdery nature and the difficulty of assembling them into mechanically stable macroscopic composites. To address this, successfully synthesized 90 wt % nanoMOF (aluminum fumarate) loaded directional aerogels (AlFA-3-10) using polyvinyl alcohol (PVA) as an adhesive, which demonstrates robust strength longitudinally and transversely. Our uranium adsorption experiments reveal that at a pH of 8 (akin to that of seawater), the AlFA-3-10 achieves a maximum adsorption capacity of 1146.25 mg g-1, maintaining this exceptional performance over five cycles. Notably, in simulated seawater, AlFA-3-10 exhibits high selectivity for uranyl ions with minimal interference from other ions. The directional pores within AlFA-3-10 facilitate fluid transmission and exchange, ensuring optimal contact between the MOF and uranyl ions, thereby enhancing electrostatic attraction and electron transport for improved capture efficiency. This streamlined approach maximizes the intrinsic potential of nano-MOFs and heralds a new era for their integration into macroscopic composite materials.

Uranium Removal from Aqueous Solutions by Aerogel-Based Adsorbents-A Critical Review

Aerogels are a class of lightweight, nanoporous, and nanostructured materials with diverse chemical compositions and a huge potential for applications in a broad spectrum of fields. This has led the IUPAC to include them in the top ten emerging technologies in chemistry for 2022. This review provides an overview of aerogel-based adsorbents that have been used for the removal and recovery of uranium from aqueous environments, as well as an insight into the physicochemical parameters affecting the adsorption efficiency and mechanism. Uranium removal is of particular interest regarding uranium analysis and recovery, to cover the present and future uranium needs for nuclear power energy production. Among the methods used, such as ion exchange, precipitation, and solvent extraction, adsorption-based technologies are very attractive due to their easy and low-cost implementation, as well as the wide spectrum of adsorbents available. Aerogel-based adsorbents present an extraordinary sorption capacity for hexavalent uranium that can be as high as 8.8 mol kg−1 (2088 g kg−1). The adsorption data generally follow the Langmuir isotherm model, and the kinetic data are in most cases better described by the pseudo-second-order kinetic model. An evaluation of the thermodynamic data reveals that the adsorption is generally an endothermic, entropy-driven process (ΔH0, ΔS0 > 0). Spectroscopic studies (e.g., FTIR and XPS) indicate that the adsorption is based on the formation of inner-sphere complexes between surface active moieties and the uranyl cation. Regeneration and uranium recovery by acidification and complexation using carbonate or chelating ligands (e.g., EDTA) have been found to be successful. The application of aerogel-based adsorbents to uranium removal from industrial processes and uranium-contaminated waste waters was also successful, assuming that these materials could be very attractive as adsorbents in water treatment and uranium recovery technologies. However, the selectivity of the studied materials towards hexavalent uranium is limited, suggesting further developments of aerogel materials that could be modified by surface derivatization with chelating agents (e.g., salophen and iminodiacetate) presenting high selectivity for uranyl moieties.

Explorations on efficient extraction of uranium with porous coal fly ash aerogels

In order to explore a suitable uranium adsorbent with the advantages of low-cost, recyclability and high efficiency, porous coal fly ash aerogels with different size of coal fly ash were synthesized. Among them, PCFAA-1250 (prepared with 1250 mesh coal fly ash (CFA)) showed better adsorption performance and the maximum adsorption efficiency even approached 96.5% (C₀ = 10 mg L^-1, m/V = 1.0 g L^-1, T = 298 K, t = 24 h and pH = 3.0), which was higher than most of previous adsorbents. Langmuir and pseudo-second-order models were more likely to be used to determine the removal behavior of uranium on PCFAA, illustrating that the adsorption reaction was uniform chemisorption. Meanwhile, the adsorption process on PCFAA was spontaneous. Notably, the desorption efficiencies of all of PCFAA were more than 80% after five cycles, which suggested that PCFAA possessed good recyclability, especially PCFAA-1250. Besides, the adsorption mechanism was further revealed via XPS and the uranium ions were immobilized on the surface of adsorbents through complexation. Based on above conclusions, it could be concluded that PCFAA-1250 had the potential to be a candidate for the extraction of uranium from wastewater.

Construction of an egg-like DTAB/SiO2 composite for the enhanced removal of uranium

For the past few years, the environmental safety problems of radioactive nuclides caused wide public concern. In this work, the dodecyl trimethyl ammonium bromide-modified silicon dioxide composite (DTAB/SiO₂) was synthesized for the elimination of uranium. The dodecyl trimethyl ammonium bromide can decorate the surface of the silicon dioxide and change its surface topography, which can offer more active sites and functional groups for the combination of U(VI). The removal capacity of U(VI) on DTAB/SiO₂ reached 78.1 mg/g, which was greater than that of the silicon dioxide nanopowder. In the adsorption process, the surface oxygen-containing functional groups formed surface complexation with uranium. The results may provide helpful content to eliminate U(VI) and expand the application of surfactant in radioactive nuclide cleanup.

Amidoxime modified Fe3O4@TiO2 particles for antibacterial and efficient uranium extraction from seawater

Uranium extraction and recovery play a critical role in guaranteeing the sustainable nuclear energy supply and protecting the environmental safety. The ideal uranium sorbents possess high adsorption capacity, excellent selectivity and reusability, as well as outstanding antimicrobial property, which are greatly desired for the real application of uranium extraction from seawater. To address this challenge, a novel magnetic core-shell adsorbent was designed and fabricated by a facile method. The obtained amidoximed Fe₃O₄@TiO₂ particles (Fe₃O₄@TiO₂-AO) achieved equilibrium in 2 h and the maximum adsorption capacity calculated from Langmuir model is 217.0 mg/g. The adsorption kinetics followed the pseudo-second-order model. Meanwhile, the Fe₃O₄@TiO₂-AO exhibited great selectivity when competitive metal ions and anions coexisted. In addition, the magnetic Fe₃O₄@TiO₂-AO could be conveniently separated and collected by an external magnetic field, the regeneration efficiency maintained at 78.5% even after ten adsorption-desorption cycles. In natural seawater, the uranium uptake reached 87.5 μg/g in 33 days. Furthermore, the TiO₂ contained adsorbent showed effective photo induced bactericidal properties against both E. coli and S. aureus. The Fe₃O₄@TiO₂-AO with great U(VI) adsorption performance is highly promising in uranium extraction and reclamation.

Removal of agricultural wastewater pollutants by integrating two waste materials, fish scales and neem leaves, as novel potential adsorbent

Only 2.5% of the world's water is fresh, despite the fact that water covers approximately 70% of the planet. This water is used for several recreational purposes and gets polluted by wastewater disposal directly into freshwater bodies. Effluents dispersed into water bodies could be from various sources like industries, households, and agricultural activities. These effluents comprise heavy metals and chemical wastes directly released into water bodies without treatment and could include major contaminants like nitrates, nitrites, ammonia and phosphates. The present study mainly focuses on removal of four significant pollutants from agriculture wastes, i.e., nitrates, nitrites, ammonia, and phosphates. These pollutants are removed using adsorbents via a process known as adsorption. Adsorbents used in the study are fish scales and neem leaves. Several studies have been carried out to measure the efficiency of adsorbents in the removal of contaminants. These studies include equilibrium studies, kinetic studies and isotherm studies. Based on a complete analysis and results obtained, 95% to 99% of contaminants can be removed effectively with an adsorbent dosage of 0.4g (0.2 g of fish scale and 0.2 g of neem leaves powder), optimum pH of 6 and at 303K constant temperature. The dosage variance stems from changing the dosages of two adsorbents in three ways, i.e., by taking both adsorbents in equal dosages, and increasing the dosage of one adsorbent compared to the other and vice versa. The contact time varied from 0 to 140min and the Initial concentration of pollutants has also been varied from 30 to 70 mg/L. In addition to the above variations, thermodynamic studies were also done, and based on the negative values of ΔG and positive value of ΔH and ΔS, it is evident that the reaction of novel adsorbent (combination of fish scales and neem leaves) is spontaneous and endothermic.

High effective enrichment of U(VI) from aqueous solutions on versatile crystalline carbohydrate polymer-functionalized graphene oxide

The removal of uranium on various sorbents has been widely employed in recent times. However, the limited sorption capacities of these sorbents inhibit the actual application of the radionuclide in actual environments. The development of a novel material with high sorption capacity and superior regeneration for the removal of uranium is highly desirable. Therefore, a versatile class of crystalline carbohydrate polymers (COF) was prepared from organic compounds. Moreover, COF-functionalized graphene oxide (COF/GO) was synthesized and tested for the removal of U(VI) from aqueous solutions. The batch characterization showed that COF was vertically oriented on the surface of GO using diboronic acid as nucleation sites. The maximum removal capacity of U(VI) on COF/GO reached 117.67 mg g-1, and was attributed to a huge void ratio and various oxygen-bearing functional groups. In addition, the inner-sphere surface-complexation dominated the U(VI) removal, and the adsorption mechanism of inner-sphere surface-complexation was transferred into surface precipitation with increasing reaction time. COF/GO can be converted into conductive carbon and reduced GO (C/rGO) nanocomposite, which has high specific capacitance. These results suggested that GO-based materials can be considered as promising candidates for the enrichment of U(VI) and energy storage.

Uranium uptake from wastewater by the novel MnxTi1-xOy composite materials: Performance and mechanism

The novel Mn_xTi_1-xO_y composite materials with different mole ratios (Mn to Ti = 3:7, 5:5 and 7:3) were prepared to remove uranium species from wastewater. These composite materials were characterized by various techniques, such as thermogravimetric analysis (TG), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) and scanning electron microscopy (SEM). It was found that the chitosan in Mn_xTi_1-x-Chi were completely removed after calcination at 650 °C and Mn_xTi_1-xO_y composites possessed uniform distribution of the porous structure as well as plentiful hydroxyl-containing groups. Moreover, the as-prepared Mn_xTi_1-xO_y composite materials were applied to remove uranium from solution to evaluate the adsorption performance. It was found that the Mn_0.5Ti_0.5O_y possessed relatively excellent uptake performance for uranium comparing with the Mn_0.3Ti_0.7O_y and Mn_0.7Ti_0.3O_y and its maximum uptake capacity and efficiency reach 695.2 mg/g and 98.6% (pH = 4, m/V = 0.1 g/L, T = 298 K), respectively, which were much superior than most of reported materials based on titanium oxide or manganese oxide. Besides, the uranium uptake on Mn_0.5Ti_0.5O_y was independent on ionic strength and it had considerable reusability, which might be the necessary condition for Mn_0.5Ti_0.5O_y to be applied in uranium uptake from uranium-containing wastewater. As a candidate adsorbent, Mn_0.5Ti_0.5O_y possessed a high potentiality to remove uranium from wastewater.