Removal Of Uranium Research Articles

Removal of uranium by APG/TAS antifreeze foam detergent with high foaming property

The environmentally friendly antifreeze foam detergent was synthesized from the biomass-based surfactants alkyl polyglucoside (APG), tea saponin (TAS), waterborne polyurethane (WPU), tartaric acid (TA), and sodium chloride (NaCl) in order to remove radioactive contamination on the surface of nuclear emergency and decommissioning facilities in low temperature environment. Additionally, the composition of foam detergent was optimized by response surface methodology. The foaming, stability, wall-hanging property of antifreeze foam detergent and its decontamination properties of simulated radioactive pollution under low temperature environment were studied. The surface tension, viscosity, and wettability of antifreeze foam detergent and the decontamination mechanism at low temperature were analyzed. The results show that at the low temperature of − 10 ºC, the foaming multiple of the foam detergent is 14.37, the half-life is 44.43 min, and the wall-hanging time on the surface of vertical ceramic tile is 60 min. Within 30 min, the decontamination factors of simulated radioactive contamination on the surface of the glass, ceramic tile, stainless steel, and lacquered board by antifreeze foam detergent are 17.83, 12.82, 12.03, and 14.83, respectively. Environmentally friendly antifreeze foam detergent with high foaming property, outstanding wall-hanging property, and decontamination ability has broad application prospects in nuclear emergency and decommissioning of nuclear facilities in low temperature environments in winter.

Efficient visible-light-driven photoreduction of U(VI) by carbon dots modified porous g-C3N4

The efficient removal of uranium from radioactive wastewater is of great significance for the ecological environment safety and sustainable development of nuclear energy. Herein, the carbon dots modified porous graphitic carbon nitride (CNCD) was fabricated and used for photoreduction of U(VI) under visible LED light irradiation. The removal rate of U(VI) by CNCD-2 could reach more than 95 % over a wide range of U(VI) concentration. In addition, the CNCD-2 showed excellent selectivity and recyclability for photoreduction of U(VI). Further mechanism studies showed that the high photocatalysis activity of CNCD-2 was attributed to the effective separation of photoinduced electron-hole pairs, strong visible light absorption capacity and narrow bandgap. The U(VI) was activated by both photoinduced e- and •O2– in the process of photoreduction, and then immobilized by transforming it to metastudtite ((UO2)O2·2H2O). These results indicate that the CNCD is a promising material for remediation of uranium-containing wastewater under visible light irradiation.

Highly efficient adsorptive extraction of uranium from wastewater by novel kaolin aerogel

An environment-friendly, low-cost and efficient kaolin aerogel adsorbent (named as KLA) was synthesized via a freeze-drying-calcination method to solve the defect of low uranium removal rate for kaolin (KL). The removal rate of uranium on KLA reached 90.6 %, which was much higher than that of KL (69.2 %) (C0 = 10 mg L−1, t = 24 h, pH = 5.0, T = 298 K and m/V = 1.0 g L−1). The uranium removal behavior on KLA was satisfied with Pseudo-second-order and Langmuir model, which meant that the uranium ions were immobilized on the surface of KLA via chemical reaction. Meanwhile, high temperature was in favor of the removal of uranium on KLA, indicating that the removal process was a spontaneous endothermic reaction. Compared with KL, KLA also presented better cycle ability and its removal rate of uranium was up to 80.5 % after three cycles, which was still higher than that of KL at the first cycle (74.5 %). On basis of the results of SEM, XRD, FT-IR and XPS, it could be concluded that uranium ions were adsorbed by KLA via complexation. Hence, KLA could be regarded as a feasible candidate for the removal of uranium from aqueous solution.

Fabrication of novel heterojunction of (1D) Nb2O5 nanorod/(0D) CdS nanoparticles for efficient removal of U(VI) from water

As an effective treatment method for uranium removal in wastewater, the application of photocatalytic reduction has attracted extensive attention. To improve the optical performance of Nb2O5, CdS nanoparticles were introduced via a one-step hydrothermal method. Then the characterization by various methods (e.g. XRD, SEM, TEM, XPS and UV–vis DRS) were used to determine the structural and optical properties of the heterojunction of Nb2O5 nanorod/CdS nanoparticles (NC). It clearly confirmed that the successful construction of the heterojunction widened the visible light absorption range, narrowed bandgap (∼2.11 eV), promoted the charge transfer and enhanced the separation efficiency of photoinduced electron-hole pairs and further improved the photoreduction activity. During the photocatalytic degradation process, the results showed the photocatalyst with the Nb/Cd molar ratio of 1/3 (NC-3) displayed the best removal of U(VI), with a removal efficiency of 97% in 90 min adsorption and 150 min visible light irradiation at the pH=6. The NC-3 photocatalyst was relatively stable and exhibited good recyclability in during the cyclic experiments. In the end, it was proposed that e- and O2- radicals played important roles in the process of the reduction of U(VI).

Highly Efficient Electrocatalytic Uranium Extraction from Seawater over an Amidoxime-Functionalized In-N-C Catalyst.

Seawater contains uranium at a concentration of ≈3.3 ppb, thus representing a rich and sustainable nuclear fuel source. Herein, an adsorption–electrocatalytic platform is developed for uranium extraction from seawater, comprising atomically dispersed indium anchored on hollow nitrogen‐doped carbon capsules functionalized with flexible amidoxime moieties (In–N x –C–R, where R denotes amidoxime groups). In–N x –C–R exhibits excellent uranyl capture properties, enabling a uranium removal rate of 6.35 mg g−1 in 24 h, representing one of the best uranium extractants reported to date. Importantly, In–N x –C–R demonstrates exceptional selectivity for uranium extraction relative to vanadium in seawater (8.75 times more selective for the former). X‐ray absorption spectroscopy (XAS) reveals that the amidoxime groups serve as uranyl chelating sites, thus allowing selective adsorption over other ions. XAS and in situ Raman results directly indicate that the absorbed uranyl can be electrocatalytically reduced to an unstable U(V) intermediate, then re‐oxidizes to U(VI) in the form of insoluble Na2O(UO3·H2O) x for collection, through reversible single electron transfer processes involving InN x sites. These results provide detailed mechanistic understanding of the uranium extraction process at a molecular level. This work provides a roadmap for the adsorption–electrocatalytic extraction of uranium from seawater, adding to the growing suite of technologies for harvesting valuable metals from the earth's oceans.

High-speed and efficient removal of uranium (VI) from aqueous solution by hydroxyapatite-modified ordered mesoporous carbon (CMK-3).

In recent years, the synthesis and application of green, cost-effective, and sustainable materials for uranium (VI) removal was significant to environmental protection. The ordered mesoporous carbon (CMK-3) supported different mass of hydroxyapatite materials (HAP@CMK-3) were facilely synthesized via hydrothermal method. The resultant materials were characterized by XRD, FT-IR, BET, SEM, TEM mapping, and XPS, and implemented for immobilizing U(VI). Not only the specific surface area of HAP (7.01 m2/g) was increased by the loading on CMK-3 (818.37 m2/g), but also the adsorption capacity of CMK-3 was increased by HAP modification. Impressively, HAP@CMK-3 exhibited highly adsorption capacity of U(VI) with the increase of HAP deposition and was capable of achieving fast reaction. Therein to, the specific surface area of HAP@CMK-3(2:1) was 253.68 m2/g, as well as the adsorption capacity was up to 1072 mg/g (fitted by Langmuir isotherm, at pH=3.0, 298 K) and the adsorption process was completed in 30 min (followed by pseudo-second-order kinetic). The adsorption mechanisms of U(VI) on HAP@CMK-3 involved electrostatic forces, ionic interactions, and chemical complexation. This work offered new avenues to address the limitations of cost and less secondary pollution for the removal of U(IV) from wastewater.

Ultrahigh efficient and selective adsorption of U(VI) with amino acids-modified magnetic chitosan biosorbents: Performance and mechanism

Exploiting eco-friendly, highly controlled preparation and convenient solid-liquid separation adsorbent to separate uranium from aquatic medium is of importance and in demand. In this study, magnetic ferroferric oxide nanoparticles synthesized through a facile hydrothermal reaction was cross-linked with chitosan. The intermediate product was subsequently chemically grafting with four amino acids such as alanine, serine, glycine or L-cysteine to produce Ala-MCS, Ser-MCS, Gly-MCS and Cys-MCS. The resultants were verified by SEM, EDS, XRD, VSM, FT-IR and XPS. Adsorption of uranium with amino acids-modified magnetic chitosans were carried out. The parameters that affected the adsorption ability, selectivity toward uranium, and reusability have been illustrated. pH 6.5 was the most beneficial for the adsorption. The saturation adsorption capacity of Ala-MCS, Ser-MCS, Gly-MCS, Cys-MCS were found as 658.88 mg/g ± 1.0 %, 616.10 ± 0.3 % mg/g, 646.38 ± 1.8 % mg/g, 653.96 ± 3.4 % mg/g and 409.15 ± 4.6 % mg/g, respectively. The adsorption process was analyzed using kinetics (pseudo-first-order, pseudo-second-order and intraparticle diffusion models) and isotherms models (Langmuir and Freundlich models). The adsorption of uranium on Ala-MCS, Ser-MCS, Gly-MCS and Cys-MCS happened on monolayer and were controlled by chemisorption. The certified high adsorption amount and efficient solid-liquid separation proved amino acids-modified magnetic chitosan are promising adsorbents for removal of uranium from wastewater.

Microwave-assisted preparation of Mn3O4@sepiolite nanocomposite for highly efficient removal of uranium

Nuclear energy is an important alternative energy source to non-renewable fossil fuels. Nevertheless, the nuclear contamination associated with nuclear activities and wastes is a formidable concern worldwide. Uranium is one of the most commonly used and discharged radionuclides, and hexavalent uranium [U(VI)] has significant mobility owing to its good solubility in water, leading to serious environmental and health risks. However, facile and economical solutions to effectively treating U(VI)-contaminated water are still limited. Herein, Mn3O4 nanoparticles were dispersedly anchored on sepiolite nanofibers via a facile microwave-assisted method for adsorbing U(VI) from aqueous solutions. Batch adsorption experiments showed that the nanocomposite possessed faster removal kinetics and greater removal capacity than the individual sepiolite and Mn3O4, as well as better removal performance than many reported inorganic and organic adsorbents. The nanocomposite can also reduce the U(VI) concentrations to far less than the standard of drinking water. Furthermore, a systematic investigation of the adsorption mechanism revealed that the nanocomponents Mn3O4 and sepiolite were responsible for the high-affinity U(VI) capture through the bonding of ≡Mn–O–U(VI) and ≡Si/Mg–O–U(VI), respectively, but the loaded Mn3O4 nanoparticles dominated the adsorption. Given that the simple synthesis and excellent U(VI) removal performance, the Mn3O4@sepiolite nanocomposite holds great promise for practical applications in radioactive uranium treatment.

Design of a renewable hydroxyapatite-biocarbon composite for the removal of uranium(VI) with high-efficiency adsorption performance

The hydroxyapatite-loaded swine manure derived-biocarbon was successfully prepared by pyrolysis method for the adsorption of uranium(VI). The results of the adsorption experiments displayed that the adsorption behaviors for uranium(VI) of biocarbon did almost not depend on the interfering ions except Al3+, Ca2+ and CO32−, showing the high selectivity of the composites for uranium(VI). The maximum static and dynamic removal capacity of the hydroxyapatite-biocarbon composites to uranium(VI) were 834.8 and 782.8 mg/g (pH = 3, m/V = 0.1 g/L and T = 298 K), far exceeding other reported biocarbon and hydroxyapatite materials, which indicated that the hydroxyapatite-biocarbon composites possessed an application potential in adsorption. After five cycles of adsorption–desorption processes, the removal efficiency of the hydroxyapatite-biocarbon composite for uranium(VI) was 93.2% (Ci = 5 mg/L, pH = 3, m/V = 0.1 g/L and T = 298 K), revealing that the composite had excellent stability and reusability. Moreover, the capture mechanisms of the hydroxyapatite-biocarbon composite for uranium(VI) included ion exchange and complexation, which was ascribed to the ample active adsorption sites (–OH and PO43−). Therefore, the hydroxyapatite-loaded swine manure derived-biocarbon would be a potential material to effectually separate uranium(VI) from solution.Graphical abstract

A novel solar-powered electrochemical mineralization system for persistent remediation of uranium-contaminated groundwater

Reduction of the migratory ability of uranium via reduction, co-precipitation or immobilization is a widely used technology for remediation of uranium contaminated groundwater (UCG). However, the re-released uranium due to environmental alterations such as oxidation, acid dissolution, or microbial decomposition limits the long-term effect of UCG remediation. Here, we developed a novel solar-powered electrochemical mineralization (SPEM) system for persistent remediation of UCG under laboratory conditions. The SPEM system incorporates uranium into magnetite crystal to achieve long-term stability of uranium. The effects of photoelectric conversion, subsurface void fraction, groundwater seepage velocity, and electrode configuration on uranium removal were systematically analyzed. The results showed that the remediation system had excellent adaptability to complex water quality and geological conditions, and could remediate large-area contamination. After 12 h of persistent treatment, the system with newly hexagonal two-dimensional electrode configuration (1A6C) reduced uranium concentration by more than 85% in simulated subsurface environment. The mineralized uranium was not re-released within continuous rinsing of treated regions using an acid solution (pH = 3.0), for 370 h. The developed method solely requires metallic iron as a raw material, which has high and long-term efficiency, is eco-friendly, simple, and widely applicable, thus reliable for the remediation of deep UCG.

Amidoxime functionalized chitosan for uranium sequestration in vivo

Amidoxime functionalized chitosan (AC) was recommended as a chelator for uranium sequestration in vivo in this study, and the structure-activity relationship was also explored. Compared with ZnNa3-DTPA, which was a commercial uranium mobilization drug, AC exhibited excellent biocompatibility and uranium removal efficiency, whether by injection or orally, which could reduce the amounts of uranium deposited in kidneys and femurs by up to 43.6% and 32.3%. In particular, ACs still possessed the ability to mobilize uranium in vivo even if administration was delayed for 72 h.

Synthesis of bimetallic Metal-Organic Frameworks composite for the removal of Copper(II), Chromium(VI), and Uranium(VI) from the aqueous solution using fixed-bed column adsorption

NiCo(BDC) bimetallic Metal-Organic Framework (MOF) is impregnated with MnO2 particles to synthesize a highly stable NiCo(BDC)@MnO2 composite. This MOF composite is applied for the removal of Copper (II), Chromium (VI), and Uranium (VI) heavy metal ions from aqueous solutions using batch adsorption and the fixed-bed column method. The physicochemical properties of the composite were analyzed by Fourier transform infrared spectrometry (FTIR), powder X-ray Diffraction (PXRD), Scanning Electron Microscope (SEM), and Brunauer−Emmett−Teller (BET) analysis. TG-DTA analysis shown the composite MOF is thermally stable up to 450°C. X-ray Photoelectron Spectroscopy (XPS) analysis confirms the presence of Nickel, Cobalt, and Mn. The fixed-bed column adsorption experiments on Cu(II), Cr(VI), and U(VI) were conducted to understand the effect of bed height, flow rate, and initial concentration on adsorption efficiency. NiCo(BDC)@MnO2 MOF composite showed a high adsorption capacity of 756.82 ​mg/g for Cu(II), 111.22 ​mg/g for Cr(VI), and 365.25 ​mg/g for U(VI) were examined by the Langmuir isotherm model. The equilibrium studies specified that Cu(II), Cr(VI), and U(VI) adsorption follows pseudo-second-order kinetics in the batch adsorption process and Thomas, Yoon-Nelson, Adam, and Bohart model in fixed-bed column adsorption, which indicates that chemisorption and surface complexation are maybe the primary mechanisms.

Application of potassium titanium ferrocyanide for the removal of uranium from aqueous solution: Efficiency and mechanism

Application of potassium titanium ferrocyanide for the removal of uranium from aqueous solution: Efficiency and mechanism

Removal of uranium from nuclear effluent using regenerated bleaching earth steeped in β‒naphthol

The intensification and adsorption of uranium on different adsorbents are considered an operative substitute technique for extraction from nuclear effluent. Many synthetic adsorbent materials have recently been developed for the removal of uranium from aqueous solution. Latterly, clay is a fundamental adsorbent to be considered in uranium recovery owing to the promising sorption properties. In this study, a spent bleaching earth from an edible oil manufacturing was remedied with a view to get rid of the edible oil remnants and then steeped in β‒naphthol to promote its adsorption characteristics. The clay is characterized by X‒ray Fluorescence (XRF), Fourier Transform Infrared Spectrometer (FTIR), surface area analyzer, Scanning Electron Microscope (SEM), and Energy-dispersive X‒ray spectroscopy (EDX). The experiments have been conducted upon adsorption efficiency of uranium to optimize the influence of pH value, agitation time, clay dosage, initial uranium ions concentration, and system temperature The uptake capacity of the new adsorbent is 175.10 mg g−1; it was been attained at pH 4.5, 60 min, and 25 °C. Both of the kinetic and isotherm of adsorption process were calculated and the data work in with pseudo‒first‒order kinetic model along with Langmuir‒Freundlich isotherm. Furthermore, the thermodynamic study implies the spontaneousness and exothermicity of the adsorption process of uranium ions. The negative value of ΔS° refers to the practicality of adsorption of uranium ions and the mitigation in randomness for the new adsorbent clay.

Uranium in groundwater in parts of India and world: A comprehensive review of sources, impact to the environment and human health, analytical techniques, and mitigation technologies

Uranium concentration/contamination in groundwater is currently a subject of concern all over the world due to related severe health problems to humans, as groundwater is the main drinking water source in rural and urban India and also in several parts of the world. Uranium concentration in groundwater in shallow aquifers in various states such as Punjab, Rajasthan, Karnataka Telangana, and Madhya Pradesh of India varies from 0 to 1443 ng/ml exceeding the permissible levels by WHO for drinking water (30 ng/ml), at several places. Very high concentrations ranging up to 1400 ng/ml were reported in some areas in other countries such as Canada, the USA, Mongolia, Burundi, Zambia, Nigeria, South Korea, Pakistan, Jordon, Afghanistan, China, and Myanmar. Various natural aspects which influence the uranium concentration in groundwater such as bedrock geology, water chemistry, and redox conditions, and anthropogenic sources such as mining activities (uranium, coal, and phosphate rock), nuclear activities, agricultural practices of using phosphate fertilizers, and prevalence of excessive nitrate in some areas, are described with examples. Some of the important analytical techniques for the precise and accurate determination of elemental and isotopic concentrations of uranium in water samples, such as LED fluorimetry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), high-resolution ICP-MS (HR-ICP-MS), and multi-collector ICP-MS (MC-ICP-MS), are described. A number of advancements have taken place in remediation technologies for the removal of uranium in drinking water using different physical, chemical, and biological methods including rainwater harvesting. Various mitigation strategies for the effective removal of uranium from water during treatment, such as bioremediation using biochars from different sources, nanoparticle technology, and adsorption by magnesium (Mg)-iron (Fe)-based hydrotalcite-like compounds (MF-HT), are described in detail.

Insights into enhanced elimination of U(VI) and Eu(III) by amidoxime-functionalized Ti3C2Tx MXenes

Although two-dimensional transition metal carbides and carbonitrides (MXenes) are becoming increasingly popular in contaminant remediation field, the preparation of MXene nanosheets that can efficiently eliminate the target pollutants still deserves in-depth investigation. Here we produced amidoxime Ti3C2Tx nanosheets (TC-AO), which were efficient radionuclide adsorbents with high stability and positive affinity, by introducing the amidoxime group into the Ti3C2Tx MXene surface through grafting by diazonium salt. The high stability and abundant functional groups of TC-AO were demonstrated by different characterization techniques such as scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), and X-ray photoelectron spectroscopy (XPS). Multiple factors affecting the radionuclide removal performance were explored, including reaction time, temperature, pH, ionic strength, anions and cations. The experimental results demonstrated that the radionuclide uptake by TC-AO was a heat-absorbing, spontaneous single-molecule chemisorption process and was consistent with the pseudo-secondary and Langmuir models. When pH < 6, the mechanism of uranium removal was inner complexation, and as the pH continued to increase, uranium removal shifted to outer complexation. Furthermore, the results certificated that TC-AO exhibited fast reaction kinetics (reaching equilibrium in about 20 min), excellent removal efficiency (279.57 mg U·g−1 and 73.99 mg Eu·g−1), outstanding selectivity and good stability. The studies showed that TC-AO had good stability and functionality, which was not only valuable for the design of MXene based adsorbents, but also provided a meaningful option for the extraction of radioactive pollutants from wastewater.

Effect of genetic properties of Khiagda uranium deposits on the choice of in-situ leaching technologies

Hydrogenous uranium deposits of Khiagda ore field have no equal among commercial uranium reserves recovered by the in-situ leaching (ISL) technology. Khiagda JSC carries out ISL of uranium from four uranium deposits in Khiagda field, namely, Khiagda, Vershinnoe, Istochnoe and Kolichkan. As compared to ore occurrences in alluvium in large paleovalleys and in syneclise-type and grabensyncline type artesian basins in Uzbekistan, Southern Kazakhstan, South Australia and in the TransUrals, Khiagda ore field differs by the fact that uranium sources in the catchment area locate at a distance of a few tens of kilometers from the uranium concentration zones in the reducing geochemical barriers. At the Vitim deposits, the zones of uranium removal from the Vitimkan Complex granite by surface water and groundwater and the zones of uranium concentration under the action of syngenetic and epigenetic reducers in the alluvium&ndash;proluvium deposits in paleovallyes are very closely spaced at tens and hundreds of meters to a few kilometers. Some other differences include the mostly phosphate rather than oxide and silica composition of uranium minerals and the near-modern age of ore&mdash;1.5&ndash;12.5 million years. The breakthrough mining technologies are proposed, such as: nonregular accessing of ore bodies with the nonuniform distribution of uranium; use of sodium nitrite as a uranium oxidizer; groundwater resources management in mining of weakly watered deposits; direct determination of uranium content of ore using the method of neutron&ndash;neutron logging. These technologies enhance efficiency of ISL. The further research aimed to improve the process designs is proposed to be focused on optimization of ISL borehole patterns as well as on improvement of groundwater resources management in mining weakly watered deposits.

One-pot synthesis of brewer's spent grain-supported superabsorbent polymer for highly efficient uranium adsorption from wastewater

High-efficient and fast adsorption of uranium is important to reduce the hazards caused by the uranium contamination of water environment due to the increased human activities. Herein, brewer's spent grain (BSG)-supported superabsorbent polymers (SAP) with different cross-linking densities are prepared as cheap and eco-friendly adsorbents for the first time via one-pot swelling and graft polymerization. A 7 wt% NaOH solution is used to swell BSG before grafting and subsequently neutralize the acrylic acid to control the reaction rate without producing alkaline wastewater. Compared with the traditional methods, swelling improves the grafting density and the utilization of raw materials due to the increased disorder degree of the BSG fibers. This results in the grafting of abundant carboxyl and amide groups onto the BSG backbone, forming a strongly hydrophilic polymer network of the BSG-SAP. Compared with the reference polymers without BSG, BSG-SAP presents higher adsorption capacity and enhanced reusability. The highly cross-linked BSG-SAP (BSG-SAP-H) shows an outstanding adsorption capacity of U(VI) (1465 mg/g at pH0 = 4.6), a fast adsorption rate (81% of equilibrium adsorption capacity in 15 min), and a high selectivity in the presence of competing ions. Adsorption mechanism studies reveal the involvement of amide groups, a bidentate binding structure between UO22+ and the carboxyl groups, and a cation exchange between Na+ and UO22+. More importantly, the adsorption capacity of BSG-SAP-H reaches 254.4 mg/g in the fixed-bed column experiment at a low initial concentration (c0(U) = 30 mg/L) and keeps 80% of the adsorption capacity after four cycles, indicating a great potential for uranium removal from wastewater. This work shows a suitable approach to explore the untreated biomass to prepare SAP with enhanced adsorption performance via a general and low-cost strategy.

Unraveling the adsorption behaviors of uranium and thorium on the hydroxylated titanium carbide MXene

Hydroxylated titanium carbide Ti3C2(OH)2, a representative of MXenes, is employed to investigate adsorption behaviors for uranium and thorium using density functional theory based simulation methods. The structural analysis of the complexes compares very well to existing computational and experimental literatures. A closer look at the adsorption configurations and energies indicates that the main adsorption sites are deprotonated Os atoms of the OH groups terminated on the Ti3C2(OH)2 MXene surface. The most stable models for U(VI) and Th(IV) adsorbed on the Ti3C2(OH)2 MXene in the gas phase are bidentate and tridentate configurations, respectively. The adsorption ability of Th(IV) on the Ti3C2(OH)2 MXene is stronger than that of U(VI). More importantly, the aqueous solution has a remarkable effect on the coordinated environment of uranyl and Th4+ ions in the binding configurations. Uranyl and Th4+ ions adsorbed on the Ti3C2(OH)2 MXene in the aqueous environment form pentavalent coordinated structures. Extra OH– ligands from water molecules are found to interact with U and Th atoms compared with the adsorption configurations in the gas phase. Moreover, U-Oax double bonds in the uranyl break to form U-OH bonds in the adsorption model. For all the stable adsorption configurations, the coordinating interaction is the dominant factor, and Th-Os bonds present more covalent nature than U-Os bonds due to the larger charge transfers between Th and Os atoms. This work gives supplement to the experimental observations and will provide deeper insights into the physical chemistry behind the removal of uranium and thorium by using MXenes.

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 78.1mg/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.