Uranium Removal Efficiency Research Articles

Efficient extraction of Uranium (VI) from aqueous solution by LDH/MOF composites

Study on uranium adsorption materials is crucial in addressing uranium pollution and safeguarding water resources. In this paper, a novel Ni/Co‐LDH@ZIF‐67/8‐MOF (LDH/MOF) composite was fabricated by loading ZIF‐67/8‐MOF on the surface of Ni/Co‐LDH with silane coupling group as bonding agent. The LDH/MOF composite was tested by XRD, FT‐IR, SEM, TGA, and XPS methods. The LDH/MOF composite exhibited exceptional uranium (U (VI)) adsorption capacity, with the Langmuir isotherm model estimating a maximum adsorption capacity of 617.33 mg/g, and the adsorption process followed quasi‐second‐order kinetics. Notably, ultrasonic mixing achieved equilibrium in a mere 5 minutes, outperforming traditional oscillation mixing by a considerable margin, offering new possibilities for enhancing uranium removal efficiency. Furthermore, thermodynamic analysis revealed the spontaneous and endothermic nature of U (VI) adsorption onto LDH/MOF. In addition, XPS investigations provided valuable insights into the adsorption mechanisms, primarily involving surface complexation, chelation, and ion exchange. These innovative findings open new avenues for the development of highly selective and efficient uranium separation methods, highlighting the promising potential of LDH/MOF as a highly prospective material for uranium separation in diverse applications, including environmental remediation and nuclear waste management.

Highly efficient uranium (VI) remove from aqueous solution using nano-TiO2-anchored polymerized dopamine-wrapped magnetic photocatalyst

Radioactive uranium containing wastewater discharged from uranium mining and associated nonferrous metallurgy posing a serious threat to human health and aquatic ecosystem. In this paper, we attempted to use photocatalytic technology to reduction U(VI) from diluted uranium-containing wastewater and recover dispersed uranium by constructing a highly efficient photocatalyst. A polymerized dopamine (PDA)-wrapped magnetic base was introduced to support spherical anchoring of TiO2 nanoparticles, and the newly designed photocatalyst (TiO2/PDA@Fe3O4) with a particle size of 450∼700 nm had a remarkable multilayer-ball structure and displayed remarkably high recyclability and photocatalytic reduction efficiency for aqueous uranium under UV radiation. Uranyl with an initial concentration of 2.0 mg/L, and solution pH of 6.0 was ∼100% removed within 40 min, and no interference by coexisting anionic and cation ions was not observed. In determination of photocatalytic mechanism, the results showed that nanoscale TiO2 particles on TiO2/PDA@Fe3O4 surface can adsorb U(VI) efficiently and reducing them under UV radiation. Furthermore, TiO2/PDA@Fe3O4 nanocomposites displayed high stability performance, the uranium removal efficiency was greater than 83.5% after six times recycle. The proposed engineered interface fabricate strategy has the potential for use in universal hydro-stable micro/nano-particle production and may contribute to more effective uranium extraction from waste liquids.

Preparation of core-shell composite materials capable of slowly releasing phosphate and their remediation performance of uranium-contaminated groundwater

Acid in-situ leach uranium mining significantly alters the geochemistry of the ore zone, and leaves uranium, residual acid, as well as other potential contaminants in groundwater, which bring harm to human health and ecological environment. Many investigators have been trying to propose remediation strategies for the uranium-contaminated groundwater. Phosphate is an effective immobilization reagent of uranium in the groundwater. However, direct injection of phosphate tends to quickly form precipitates, resulting in fast blockage of the seepage passages in the ore zone around the injection holes and hindering its diffusion. In this paper, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA with core-shell structures were prepared. Their slow-release of phosphate, the effects of pH, contact time, initial uranium concentration, and coexisting ions on their removal rate and efficiency of uranium, and their function of remediating uranium-contaminated groundwater were investigated. It was found that the increase of SA content in the outer layer of HAP@SiO2-600@25SA and HAP@SiO2-600@75SA resulted in the slow release rate of phosphate, decreasing the removal rate of uranium. The adsorption capacities of HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA from the aqueous solution at pH = 3.0 and 303 K were up to 582.6, 558.5, and 507.3 mg g−1, respectively. In addition, the materials showed excellent uranium removal performance in experiments where multiple ions coexisted. For actual acidic uranium-contaminated groundwater, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA effectively increased the pH from 2.75 to 4.40, 3.87, and 3.72, respectively, and decreased the uranium concentration from 5.12 to 0.0062, 0.0065, and 0.0058 mg L−1, respectively. The FT-IR, XRD, TEM and XPS characterizations were performed to further clarify the uranium removal mechanism, and it was found that the elimination of U(VI) was ascribed to dissolution-precipitation, adsorption and ion exchange. The results show that the core-shell composite material capable of slowly releasing phosphate is effective in remediating uranium-contaminated groundwater.

Enhancement of CdS resistance to photocorrosion and photocatalytic removal of uranyl by complexation with N-deficient g-C3N4under aerobic conditions

The effect of oxygen on the reduction of uranyl and photocorrosion of CdS remains a pressing issue when CdS is used as a photocatalyst for the removal of uranyl in uranium-containing wastewater. In this study, composites (CdS/PCN) were prepared by designing N-deficient g-C3N4 composite with CdS for efficient photocatalytic reduction of uranyl under aerobic condition. Meanwhile, a series of characterizations of the CdS/PCN composites were carried out by XRD, FT-IR, XPS, EDS and UV–vis. Surprisingly, the CdS/PCN not only showed very high photocatalytic reduction activity for uranyl under aerobic condition, but also the photocorrosion of CdS by oxygen and h+ was inhibited. With a starting uranium (VI) concentration of 20 ppm, the uranium (VI) removal efficiency could reach 97.33% (dark: 30 min, light: 10 min). Interestingly, the removal efficiency was better in air condition than in pure nitrogen or 30% oxygen atmosphere, i.e. a proper amount of oxygen has accelerated the reduction reaction, while excess oxygen weakened the reduction. Finally, a new mechanism of reduction of uranyl by CdS/PCN photocatalyst was given under aerobic condit ions. This work presents a novel strategy for reduction of U(VI) by photocatalysis and the inhibition of photocorrosion of photocatalysts under aerobic conditions.

Magnetite/β-cyclodextrin/fly ash composite as an effective and recyclable adsorbent for uranium(VI) capture from wastewater

As a novel adsorbent for the separation of uranium(VI) from wastewater, Magnetite/β-cyclodextrin/fly ash composite (Fe3O4/β-CD/FA) was first prepared via a chemical coprecipitation technology. The characterization results indicated that Fe3O4 and β-CD had been successfully loaded on FA, which had brought abundant oxygen-containing functional groups, providing numerous adsorptive sites for the removal of uranium(VI). At pH = 5.0 and T = 25 °C, the maximum uranium(VI) removal efficiency and capacity of Fe3O4/β-CD/FA were higher to 97.8% and 444.4 mg g−1, respectively. Pseudo-second-order and Langmuir models fitted better with the experimental data, illustrating that chemical adsorption dominated the uranium(VI) removal process. In addition, Fe3O4/β-CD/FA showed good anti-interference ability and recoverability. After five cycles, the removal rate of uranium(VI) on Fe3O4/β-CD/FA was still higher to 90.4%. The immobilization of uranium(VI) on Fe3O4/β-CD/FA was mainly ascribed to the synergism of redox reaction, complex reaction, chemical reaction and electrostatic interaction. Given the above, Fe3O4/β-CD/FA would be regarded as an efficacious, green and promising adsorbent for uranium(VI) separation from wastewater.

Selective removal and long-term immobilization of uranium by ultralow content Fe0 in the pores of amino functionalized silica gel

Developing a materials to realize the selective adsorption and long-term immobilization of uranium is of great significance for the effective remediation of uranium-containing wastewater. Herein, we half-filled Fe0 into SGB-NH2 mesoporous channels to prepare a composite of Fe0 and amino-functionalized silica (Fe0@SGB-NH2), and used to the selective removal of uranium in solution under aerobic conditions. It was found that solutions containing 10 mg/L U(VI) could be purified 98.96% by Fe0@SGB-NH2 in the presence or absence of Na+, K+, Mg2+, SO42 −, NO3−, HCO3− and Cl− at pH 5–9. Compared with Fe0, its saturation magnetization decreased from 81.24 emu/g to 0.78 emu/g, while the specific surface area increased from 47.895 m2/g to 504.404 m2/g, successfully preventing the agglomeration and rapid corrosion of Fe0 without reducing its activity. More interestingly, the consumption of Fe0@SGB-NH2 was only 1/28 of untreated Fe0 when identical uranium removal efficiency was achieved. Further mechanistic studies indicated that U(VI) was firstly selectively captured by amino groups on the surface of the material and then reduction or adsorption in the pore, the long and narrow mesoporous channels reduce the possibility of uranium re-oxidation, thereby significantly reducing its re-release efficiency from 21.5% to only 1.73%. Encapsulation of Fe0 within SGB-NH2 channels was found to facilitate faster removal rate and higher U(VI) reduction ratio, and reduce uranium re-oxidation, thus benefit the long-term immobilization of uranium in contaminated groundwater.

Efficient removal of trace uranium from nuclear effluents using irradiation-functionalized fibrous adsorbents with very high salt tolerance

The extraction of uranium from nuclear effluents is both conducive to the recycling of nuclear fuel and reduces environmental pollution. Adsorbents are widely regarded as the most promising materials for trace uranium extraction; however, the adsorption of trace uranium from high-salinity environments is a challenge for adsorbents used to recover uranium from nuclear effluents. In this study, four different irradiation-functionalized adsorbents were fabricated and evaluated to screen suitable adsorbents for the removal of trace uranium from nuclear effluents. We found that the adsorbent with synergistic adsorption groups (NWF-g-PGMA-AO) exhibited the most distinctive trace uranium removal efficiency and robust stability in acidic, alkaline, and high-salinity environments. It was the synergistic involvement of hydroxyls in the coordination of amidoximes with uranium that enhanced the binding energy of uranium to NWF-g-PGMA-AO, thus improving its performance. In addition, the residual uranium concentration decreased to the maximum allowable emission concentration of 50 ppb over a wide pH range, with a minimum concentration of 9.35 ppb. Interestingly, nitrate, sulfate, phosphate, and chloride anions in the effluents did not decrease the uranium removal efficiency, whereas fluoride considerably reduced the efficiency, and the removal ratio was negatively correlated with fluoride concentration. This is attributed to the formation of [UO2Fn]2−n (n = 1, 2, 3, 4) species, which exhibit a decreasing affinity for adsorbents with increasing fluorine atoms as revealed by density functional theory calculations. This work makes a stride in designing superior adsorbents with synergistic adsorption groups for extracting trace uranium from nuclear effluents.

The construction of magnetic hydroxyapatite-functionalized pig manure-derived biochar for the efficient uranium separation

In this work, three magnetic biochar-supported nano-hydroxyapatite materials were prepared by endowing different magnetic sources, which showed excellent reusability and adsorption ability. It was worth mentioning that the maximum adsorption capacity of the magnetic biochar-hydroxyapatite composite with nickel chloride as the magnetic source reached 1723.5 mg/g and the residual concentration of uranium in the solution could reach the limit standard of China for the discharge of uranium-containing wastewater at low uranium concentration. The removal efficiencies of the composite for uranium in different water systems were all higher than 90.2 %, which reflected the applicability of the composite. Besides, the material was easy to be recycled and reused due to the magnetization. After eight times of reuse, the uranium removal efficiency was still higher than 96.3 % and the magnetism was not significantly weakened. The multiple strong chemical reactions of active sites with uranium, including ion exchange, surface complexation and ionization-precipitation, were the major reason for the excellent adsorption ability. In conclusion, the magnetization of biochar-based materials might be a promising uranium adsorbent, which would open a new direction for the design of biochar-based adsorbents for uranium removal.

High Efficiency Uranium(VI) Removal from Wastewater by Strong Alkaline Ion Exchange Fiber: Effect and Characteristic.

In this study, we analyzed the removal efficiency of uranium(U(VI)) in wastewater at relatively low concentrations using strong alkaline ion exchange fiber (SAIEF). Static tests showed that the strong alkali fibers can purify U(VI) containing wastewater in a concentration range of 20-100 mg L-1 with an optimal pH of 10.5 and contact time of 15-30 min. Adsorption and desorption cycling tests indicated that, adsorbed uranium is easily desorbed by 0.1 mol L-1 HCl, and the fiber still maintained the original adsorption efficiency after eight cycles. According to dynamic penetration test results, the SAIEF saturation adsorption capacity was 423.9 mg g-1, and the effluent concentration of uranium through two series columns was less than 0.05 mg L-1, reaching the national standard for non-receiving water (GB23727-2009) SEM-EDS and FTIR analysis revealed that the functional group of SAIEF is CH2N+(CH3)3Cl-. Addotionally, the major forms of fiber exchange adsorption are (UO2)2CO3(OH)3-, UO2(CO)34- and UO2(OH)3-. The results indicate that the SAIEF is an excellent material for uranium removal.

Preparation of carboxy methyl cellulose stabilized nano-sized zero-valent iron and its properties for in situ remediation of groundwater in areas after acid in situ leach uranium mining

In this study, a highly dispersed carboxy methyl cellulose stabilized nZVI was synthesized and characterized, showing excellent uranium removal efficiency in acid in situ leach mine water.

Highly efficient separation of uranium from wastewater by in situ synthesized hydroxyapatite modified coal fly ash composite aerogel

In this work, hydroxyapatite (HAP) was in situ synthesized on coal fly ash (CFA) to prepare hydroxyapatite modified coal fly ash composite aerogel (HCFAA). The maximum removal efficiency and capability of uranium(VI) on HCFAA were 97.6 % and 205.7 mg g−1, respectively, which was much higher than those of CFA (83.6 % and 59.1 mg g−1) (pH = 3.0, m/V = 1.0 g/L and T = 298 K). The desorption efficiency of uranium(VI) by HCFAA was even more than 80 % after five cycles, demonstrating that the introduction of HAP had improved uranium(VI) removal performances. Pseudo-second-order and Langmuir models were fitted better with the experimental data, indicating the uranium(VI) removal process was a homogeneous monolayer chemisorption. Meanwhile, the uranium(VI) removal efficiency for HCFAA in actual wastewater was higher to 80.6 % and uranium(VI) could even be completely separated from actual wastewater by HCFAA during dynamic adsorption (m = 50 mg, V = 400 mL, C0 = 10 mg/L), further illustrating that the introduction of HAP was an available method to modify CFA. Characterizations results demonstrated that uranium(VI) was successfully immobilized on HCFAA through ion exchange, dissolution-precipitation and surface complexation. In conclusion, HCFAA was a prospective adsorbent for uranium(VI) separation in practical application.

Highly efficient uranium capture from wastewater by hydroxyapatite aerogels prepared with konjac gum as template

HAP aerogels with higher adsorption speed and capacity were synthesized through a combination of freeze-drying and template way using konjac gum (KGM) as template. Among them, B-HAP (HAP aerogel prepared with 0.25 g KGM as template) showed better micromorphology and structure, leading to more available sites on B-HAP, which was beneficial for the immobilization of uranium. The removal efficiency of uranium by B-HAP was 99.4% within 10 min and the maximum removal capacity was up to 2055.2 mg g−1, which was larger than other reported adsorbents. Pseudo-second-order and Langmuir models were better fitted with the adsorption behavior on HAP aerogels, indicating that uranium ions were immobilized on HAP aerogels via chemical adsorption. B-HAP also showed high selectivity, stability and durability, which was expected to be a feasible candidate for the extraction of uranium from wastewater.

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.

Investigation of adsorption properties and mechanism of uranium(VI) and europium(III) on magnetic amidoxime-functionalized MCM-41

Herein, a novel magnetic amidoxime-functionalized MCM-41 (Fe3O4@MCM-41-PDA/OA) was developed by loading Fe3O4 on amidoxime-functionalized MCM-41 via a simple strategy. The microscopic surface morphologies and structures of the as-synthesized composites were analyzed various physicochemical and spectroscopic techniques, while the experimental parameters were optimized by means of the single factor experimental methodology to improve the removal efficiency of uranium(VI) and europium(III) on Fe3O4@MCM-41-PDA/OA. The static adsorption test showed that the saturated adsorbed amounts for uranium(VI) and europium(III) were 38.11 mg/g and 25.36 mg/g, respectively. Meanwhile, the adsorption isotherm and kinetics studies revealed that elimination of the two radionuclides were a monolayer and chemisorption process, whereas the calculated thermodynamic parameters suggested that the adsorption of the two radionuclide was spontaneous and feasible. The SEM and XPS analysis conformed that immobilization of the two radionuclides was fulfilled through the binding interactions between U(VI)/Eu(III) and the amino, phenolic hydroxyls and amidoxime groups on the surface of Fe3O4@MCM-41-PDA/OA. This work provided a simple and cost-effective way to separation and enrichment of radionuclides from contaminated water.

Controllable shell corrosion of coated nanoscale zero valent iron induces long-term potentiation of its reactivity for uranium removal

Coating a soluble shell material on the surface of nanoscale zero-valent iron (nZVI) particles to eliminate the problems of agglomeration and rapid aqueous corrosion of Fe(0) in groundwater is an effective strategy for long-term maintaining uranium removal efficiency. However, the precise role of controllable shell corrosion on uranium removal mechanism remains unclear. In this study, a homogeneously dispersed Mg(OH)2 shell coated on nZVI (nZVI@Mg(OH)2) prepared by one-step surface precipitation was exploited to investigate the relationship between shell corrosion and uranium removal mechanism. The results confirm that nZVI with uniform coating shell (Mg(OH)2/Fe(0) = 1:2, mass ratio) was synthesized by simply mixing magnesium hydroxide with Fe2+ and NaBH4 solution under the flowing stream of N2 (25 ± 1 °C). The longevity and reactivity release rate of coated nZVI depended upon the initial pH value of the aqueous solution. At initial pH = 5, coated nZVI showed a high reduction activity, its ORP measured was 1.3 times that measured at initial pH = 3, and the duration could be prolonged to more than 4.5 times. The exposed Fe(0) core rapidly elimination U(VI) by synergistic attributed to the adsorptive (44.1%) and reductive (55.9%) processes after the passivation shell was eroded by reaction with H+. The results provide an efficient approach to improve the long-distance transport capacity and controllable release of nZVI, which can maintain its long-term reactivity in groundwater remediation.

Uranium sorption on oxyhydroxide minerals by surface complexation and precipitation

During the chemical weathering of the uranium mill tailings, released uranium could be immobilized by the newly formed secondary minerals such as oxyhydroxides. A deeper understanding of the interaction between uranium and common oxyhydroxides under environmental conditions is necessary. In this work, uranium sorption behaviors on Al-, Mn- and Fe-oxyhydroxide minerals (boehmite, manganite, goethite, and lepidocrocite) were investigated by batch experiments. Results showed that the uranium sorption on Al-oxyhydroxide behaved significantly differently from the other three minerals. The sorption edge of the Mn- and Fe-oxyhydroxides located around pH 5, while the sorption edge of boehmite shifted about 1.5 pH unit to near neutral. The sorption isotherms of uranium on manganite, goethite and lepidocrocite at pH 5.0 could be well fitted by the Langmuir model. Instead of surface complexation, sorption on boehmite happened mainly by uranium-bearing carbonates and hydroxides precipitation as illustrated by the characterization results. Both carbonate and phosphate strongly affected the uranium sorption behavior. The removal efficiency of uranium by boehmite exceeded 98% after three sorption-desorption cycles, indicating it may be a potential material for uranium removal and recovery.

CO2-in-Water Pickering Emulsion-Assisted Polymerization-Induced Self-Assembly of Raspberry-like sorbent microbeads for uranium adsorption

• An amino oxime functionalized raspberry-like sorbent microbeads is firstly prepared for uranium extraction. • A new idea for the controllable interface assembly of nano-sized particles was provided. • RL-SMs exhibited a remarkable uranium removal efficiency when multiple metal ions coexist. • RL-SMs shows a fast adsorption equilibrium, which only need 30 min. Highly efficient adsorption of radioactive uranium from seawater is a grand challenge of mounting severity as the energy demand increases. To address this, a salicylaldoxime functionalized raspberry-like microbeads sorbent is created to achieve highly efficient uranium adsorption via the CO 2 -in-Water Pickering emulsion-assisted polymerization-induced self-assembly method. The prepared raspberry-like microbeads sorbent with a high density of accessible functional groups exhibits the maximum uranium adsorption capacity of 41.02 mg g −1 within 30 min, the time required to reach adsorption equilibrium is shorter than most of the reported amine-oxime functionalized microsphere adsorbents. In addition, under the coexistence of high-concentration metals such as Na + , Mg 2+ , K + , Ca 2+ , etc., the raspberry-like microbeads sorbent still showed the best affinity for uranium, which is mainly benefit from the specific binding between amine oxime group and uranium. Our work not only provides a general strategy for the rapid and selective adsorption of uranium from seawater, but also provides a new perspective for the controlled assembly of NSs and the preparation of nano-hybrid materials combining the advantages of micro/nano structures.

Impact of UF6 chemical toxicity on design and emergency response of a nuclear fuel fabrication facility in China

UF6 leakage accident is one of the main accidents considered by nuclear fuel fabrication facilities. It is generally believed that the emergency class of such facilities should be limited to site area emergency. In this paper, RTM-96, a consequence assessment model developed by NRC, is used to assess a nuclear fuel fabrication facility in China. The evaluation results show that from the perspective of radiation hazard, it is appropriate to limit the emergency class of UF6 leakage accident to site area emergency; but from the perspective of chemical toxicity, the hazard of HF, a highly corrosive gas formed when UF6 reacts with H2O, may cause serious impact on the public. Besides the uranium removal efficiency, HF removal efficiency must also be considered in the accident exhaust system.

Degradation of Uranium-Contaminated Decontamination Film by UV Irradiation and Microbial Biodegradation.

This research provides a complete degradation scheme for acrylic copolymer/cellulose acetate butyrate peelable decontamination films. This study analyzed the removal efficiency of uranium by peelable decontamination film. More importantly, the degradability of the films was evaluated by a combined treatment with UV radiation and microbial biodegradation. The results showed that UV radiation would rupture the surface of the decontamination films, which leaded the weight-average molecular weight decreased by 55.3% and number-average molecular weight decreased by 75.83%. Additionally, the microbial flora induced light-degradable decontamination film weight-average molecular weight and number-average molecular weight decreased by 9.3% and 30.73%, respectively. 16S rRNA microbial diversity analysis indicated that Pantoea, Xylella, Cronobacter, and Olivibacter were the major degrading bacteria genera. Among them, 4 key strains that can be stripped of decontamination films have been isolated and identified from the dominant degrading bacteria group. The results show that UV radiation combined with microbial flora can achieve rapid degradation of the decontamination films.

Highly enhanced adsorption performance to uranium(VI) by facile synthesized hydroxyapatite aerogel

In order to protect environment and save uranium resources, it was necessary to find a highly efficient adsorbent for uranium recovery from wastewater. In this work, we used a freeze-drying-calcination method to synthesize HAP aerogel to effectively remove uranium. Compared with commercially available nano-hydroxyapatite, HAP aerogel presented better adsorption performance. This was because the as-prepared HAP aerogel presented continuous porous structure, which could provide more active sites for the adsorption to uranium. The uranium removal efficiency of HAP aerogel arrived 99.4% within 10 min and the maximum adsorption capacity was up to 2087.6 mg g−1 at pH = 4.0 and 298 K. In addition, the immobilization of uranium on HAP aerogel was chemisorption, which was probably due to adsorption, dissolution-precipitation and ions exchange. These results indicated that the as-prepared HAP aerogel could be widely used as a high efficiency and potential adsorbent for the treatment of uranium-containing wastewater in the future.