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Fabricating efficient adsorbent for the removal of nuclear waste is of vital importance from the viewpoint of both environmental protection and resource reclamation. Published research has yielded several adsorbents; however, these reported materials do not possess a high removal performance for different types of nuclear waste. In this work, it is shown for the first time the synthesis of a boron‐functionalized covalent organic framework (COF) and its ionic borate counterpart. These boron‐functionalized COFs are found to show large potential for handling various nuclear wastes, including alkaline nuclear wastewater, uranium‐containing nuclear wastewater, and I2 nuclear off‐gas. The developed COF has a record NaOH uptake of 2 g g−1, an ultrahigh uranium extraction ability of 1.77 g g−1, and an ultrahigh I2 capture capacity of 9.4 g g−1. Moreover, the materials have low cost and are reusable, and thus have significant potential for handling nuclear wastes. [ABSTRACT FROM AUTHOR]

Removal of uranium(VI) from nuclear wastewater is urgent due to the global nuclear energy exploitation. This study synthesized novel sponge-like 3D porous materials for enhanced uranium adsorption by combining electrospinning and fibrous freeze-shaping techniques. The materials possessed an organic–inorganic hybrid architecture based on the electrospun fibers of polyacrylonitrile (PAN) and SiO2. As a supporting material, the surface of fibrous SiO2 could be further functionalized by cyano groups via (3-cyanopropyl)triethoxysilane. All the cyano groups were turned into amidoxime (AO) groups to obtain a amidoxime-functionalized sponge (PAO/SiO2-AO) through the subsequent amidoximation process. The proposed sponge exhibited enhanced uranium adsorption performance with a high removal capacity of 367.12 mg/g, a large adsorption coefficient of 4.0 × 104 mL/g, and a high removal efficiency of 97.59%. The UO22+ adsorption kinetics perfectly conformed to the pseudo-second-order reaction. The sorbent also exhibited an excellent selectivity for UO22+ with other interfering metal ions.

Uranium (U) is a trace radioactive element distributed within the surface and ground waters through various sources, including natural and human-made activities. This study aimed to present a holistic review of uranium removal from groundwater. According to findings present study, in ground waters the highest concentration of uranium 27 to10,100 µg/L was found in USA, and the lowest concentration was3 to 8.6 µg/L found in India, while in surface waters the highest level of uranium 0.05 to 900 µg/L was found in Turkey, and the lowest concentration was 0.13 to 590 ng/L found in Japan, and the WHO and EPA guideline value of 30 µg/L. Various treatment techniques used for uranium removal, including adsorption, conventional coagulation, chemical precipitation, bioremediation, nanofiltration and reverse osmosis, and ion exchange, have been considered widely and established to propose acceptable findings. These methods can be used in future research to remove uranium (U (IV) and U(VI)) from polluted waters in both experimental and real-world. [ABSTRACT FROM AUTHOR]

This article presents the first study on the use of alginate and moringa as an effective adsorbent for uranium treatment under various conditions. A new method of preparing adsorbents was used by adding Moringa oleifera seeds (MOS) to alginate through simple grafting. The resulting beads have a heterogeneous, sponge-like structure that is reversible. The adsorbents were tested for their ability to remove uranium ions from water and showed excellent efficiency with an adsorption capacity of 443.60 mg/g for alginate-PEI-MOS and 341.38 mg/g for alginate-Glu-MOS. Additionally, these adsorbents showed an interesting rate of swelling in water and uranium solution. The results of isotherm, and kinetic models indicate that the adsorption is monolayer, followed by multilayer adsorption after a certain concentration range with mixed adsorption (physical and chemical). Therefore, MOS could be a useful tool for adsorbing uranium from water and real wastewater. [ABSTRACT FROM AUTHOR]

The complexity of nuclear wastewater treatment motivates the design and synthesis of highly selective and stable uranium adsorbents to provide environmental remediation. Herein, a post‐synthetic modification method is adopted to synthesize two β‐ketoenamine and benzoxazole‐linked COFs decorated with abundant phosphonic groups for the uranium removal, which overcome the disadvantage of amidoxime groups with stronger affinity for vanadium than uranium. The U‐uptake capacity of β‐ketoenamine‐based TpPa‐2OH‐PHos reaches 410.9 mg g−1 (pH 5, C0 = 100 mg L−1 and m/V = 1/10 g L−1). Notably, U‐uptake capacity of TpDBD‐PHos reaches 633.3 mg g−1 at the same conditions. More abundant phosphonic groups and the synergistic effect between the benzoxazole rings and phosphonic groups may be responsible for the good uranium adsorption performance for TpDBD‐PHos. Moreover, TpDBD‐PHos exhibits a satisfactory uranium removal rate of 87.71% in actual rainwater samples. The X‐ray pHotoelectron spectroscopy (XPS) analysis suggests that the strong interaction between U(VI) and oxygen/nitrogen atoms in the frameworks plays a vital role for the adsorption of TpPa‐2OH‐PHos and TpDBD‐PHos, which agrees well with the results of density functional theory (DFT) calculations. The good chemostability and excellent selectivity demonstrate that TpDBD‐PHos is an outstanding candidate for the removal of uranium from contaminated water systems. [ABSTRACT FROM AUTHOR]

Aniline and polyaniline was successfully impregnated with Chinese D263B resin and polymerisation prepared via using polyvinyl alcohol as a surfactant and benzoyl peroxide to form impregnated D263B/aniline and D263B/polyaniline were used for enhancing the removal of U(VI) from Abu El Toyour leach liquor. The impregnated D263B/polyaniline was characterised by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). Experimental measurements have been optimised by batch extraction technique such as pH, contact time, initial U(VI) concentration, resin dosage, temperature and eluting agents. It was found that the maximum uptake capacity of Chinese D263B resin is 40 mg/g at room temperature, Chinese D263B resin with aniline is 86.95 mg/g and Chinese D263B resin with polyaniline is 121.95 mg/g. The resulted equilibrium data fitted well with Langmuir isotherm model. From kinetic parameters, it was found that U(VI) adsorption followed the pseudo-second order kinetic model. The thermodynamic parameters ΔH, ΔS and ΔG were also evaluated indicating exothermic, randomness and non-spontaneous adsorption process. U(VI) can be eluted approximately 99% from the loaded D263B/polyaniline using 1 M (1:1) NaCl/H2SO4. Finally, the optimised factors have been applied for enhanced U(VI) removal from Abu El Toyour leach liquor. [ABSTRACT FROM AUTHOR]

Adsorption is an effective technology widely used in the removal of radioactive and other heavy metal ions, the adsorbent plays critical role and development of novel adsorbents is being in urgent demand. In this work, phytic acid (PA)‐modified melamine sponge (MS) adsorbent MS@PDA@PA is prepared conveniently in green solvent water. A wide spectrum of metal ions including radioactive uranyl and transition heavy metal ions can be effectively adsorbed by the MS@PDA@PA due to non‐selectivity of phosphoric acid groups in PA. Different factors including pH of aqueous solution, contact time, and initial concentration of ions on the effect of adsorption of the resultant materials are investigated in detail, and the maximum adsorption capacities for U(VI), Pb(II), Cu(II), Cr(III) are 166.7, 168.5, 114.3, and 101.0 mg g−1 respectively at 298 K. It is notable that the MS@PDA@PA is nonflammable due to employment of MS as frame material, and the thermal stability is even improved after incorporation of PA, greatly reduce the risk of the adsorbent in the processes of storage and usage. The green yet simple synthesis and fire resistance of MS@PDA@PA make it a competitive material for practical treatment of wastewater consisting of toxic metal ions. [ABSTRACT FROM AUTHOR]

The governance of uranium tailings aims to improve stability and reduce radionuclide uranium release. In order to achieve this goal, the uranium removal solution test and uranium tailings grouting test were successively carried out using microbially induced calcium carbonate precipitation (MICP) technology. The effect of MICP on the reinforcement of uranium tailings and the synchronous control of radionuclide uranium in the tailings were discussed. The solution test results show that Sporosarcina pasteurii could grow and reproduce rapidly in an acidic medium with an initial pH of 5. The uranium concentration decreased with the increase in MICP reaction time, and the removal efficiency reached 60.9% at 24 h. In the solidification test of tailings, the strength of tailings improved significantly after 12 days of reinforcement, with an increase in the cohesion of tailings by 2.937 times and an increased internal friction angle of 8.393°. The peak stress value of solidified tailings at the surrounding pressure of 50 kPa increased by 1.87 times, and the uranium concentration in the discharge fluid decreased by 76.91% compared to the blank group. This study provides valuable insights and references for safely disposing of uranium tailings. [ABSTRACT FROM AUTHOR]

Contamination of underground water by uranium (U) and other heavy metals is a growing concern. Mesoporous silica nanoparticles (MSNs) have shown great potential as an adsorbent material for heavy metal removal. This study synthesized a novel MSN using surface-initiated atom transfer radical polymerization (SI-ATRP) and evaluated its effectiveness for removing uranium from aqueous solutions under different conditions. The particle size was reduced to 150–240 nm to enhance adsorption. Fourier transform infrared characterization and thermogravimetric analysis confirmed successful synthesis and modification. Results showed that the MSN adsorbent was highly effective in removing U, with a removal rate of 85.35% at 120 min. Temperature had a significant impact, with the highest removal rate of 96.7% achieved at 25 °C and a U concentration of 10 ppm. The highest removal rate of 91.89% was achieved at a pH of 6 and a U concentration of 50 ppm. The highest removal rate of 95.16% was achieved at 25 mg and a U concentration of 50 ppm at room temperature for 60 min. The MSNs also showed a 58.27% removal rate in a mixture solution at room temperature for 60 min. This study demonstrates the effectiveness of the MSN adsorbent for removing U under different conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The biosorption behavior and biomineralization mechanism of low concentration uranium was investigated in this study. The results showed the obvious effects of ratio of uranium and biomass concentration, contact time, and pH value. Optimum bacterium-uranium ratio(G) is about 20–50, and the optimal pH value is about 4.0–9.0. Biosorption process can be divided into three stages: fast, slow and further biosorption stage. Numerous functional groups on the cell surface such as carboxyl, hydroxyl, amide groups, phosphoric acid group and amino group rapidly adsorbed uranyl ions. Desorption that considered as a self-protective phenomenon, was obvious in the stable adsorption. Scaly shaped uranium crystal which proved to be chernikovite uramphite (NH4)(UO2)PO4·3H2O (PDF #42-0384), was formed on cell surface with long contact time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti 3 C 2 T x was phosphoric acid-functionalized by a facile post-modification approach. • The maximum U(VI) uptake capacity of as-prepared Ti 3 C 2 -APTES-PA composite reached 323 mg/g. • Ti 3 C 2 -APTES-PA showed satisfactory selectivity for U(VI) and good recyclability. • Stable coordination of phosphate groups and Ti−O terminals with U(VI) was confirmed. • A small fraction of U(VI) was reduced to U(IV) by the electron-rich Ti 3 C 2 T x MXene. The construction of novel MXene-based composites with superb abilities through functionalization is an effective strategy to enhance the potential of this emerging inorganic lamellar material for environmental adsorption applications. The present work systematically investigated the adsorption performance of Ti 3 C 2 T x MXene modified with phosphate functional groups that facilitate the capture of uranyl ions. After introducing phosphate groups via a two-step modification of 3-aminopropyltriethoxysilane (APTES) and phytic acid (PA), the synthesized Ti 3 C 2 -APTES-PA is significantly superior to pristine Ti 3 C 2 T x nanosheets in terms of adsorption capacity, adsorption selectivity and reusability for uranium. The maximum uptake capacity of Ti 3 C 2 -APTES-PA at pH = 5 reaches 323 mg/g, which is 2.5 times higher than that of unmodified MXene. Furthermore, the large selectivity coefficient (S U/M > 16.2) declares that Ti 3 C 2 -APTES-PA preferentially adsorbs uranium among substantial competing ions. Ti 3 C 2 -APTES-PA also shows good cycling performance that its adsorption capacity remained 92.3 % after 6 cycles. When it comes to treating simulated uranium tailings pond leachate and radioactive wastewater from mines, high U(VI) removal rates of 88.9 % and 96.8 % can be achieved by our ternary composite at a dosage of 0.05 g/L. The underlying adsorption mechanism was unraveled by spectroscopic analysis to be the formation of coordination complexes of uranyl ions with phosphate groups on PA and hydroxyl groups on Ti 3 C 2 T x substrate, as well as the reduction of a small amount of adsorbed U(VI) to U(IV) by MXene. The overall results imply that Ti 3 C 2 -APTES-PA is an effective uranium chelating scavenger for the treatment of environmental radioactive wastewater. [ABSTRACT FROM AUTHOR]

Herein, a series of conjugated microporous polymers (CMPs) were designed and synthesised at the molecular level. The results show that the adsorption-photocatalytic performance modulation was achieved by altering the electron transport bridges as well as adding electron adsorption groups on the CMPs, which improved the affinity for uranium and led to a more homogeneous distribution of electron holes and facilitated exciton dissociation. [Display omitted] • The adsorption-photocatalytic degradation of uranium by conjugated microporous polymers can be tuned at the molecular level and does not allow the addition of additional sacrificial agents. • Constructing more electron-withdrawing groups in polymers and enhancing the degree of conjugation can effectively promote charge transfer. • By designing the molecular structure, the band gap of the CMPs, as well as the exciton dissociation energy, was altered to facilitate carrier separation. • In the adsorption-photocatalytic synergistic strategy, excellent adsorption performance is a prerequisite for improving the efficiency of the strategy. • The PB3-AO has excellent conjugation and the best uranium affinity, with the best uranium removal performance, 99.8 % uranium removal in 100 min. • Before and after conditioning, the kinetic constants for uranium removal removal were elevated by a factor of ten from PB1-AO (0.0056 min−1) to PB3-AO (0.0557 min−1). Conjugated microporous polymers (CMPs) are potential materials for removing radioactive contaminants due to their unique properties. Herein, we designed and synthesized a series of CMPs at the molecular level by modifying the electron transport bridge and incorporating acceptor units based on the synergistic adsorption-photocatalysis strategy. The obtained CMPs exhibit a strong affinity for uranium, and their more homogeneous electronic structure becomes more efficient D-π-A electron transport chain contribute to a lower exciton dissociation energy. Further electronic excitation analysis based on time-varying density functional theory shows that the electron-hole distribution and intramolecular charge transfer of the CMPs are significantly optimized, thus enhancing photocatalytic activity. This study enhances the performance of the adsorption-photocatalytic uranium trapping strategy by precisely modulating in the synthesis and provides theoretical guidance for developing materials for treating nuclear pollution. [ABSTRACT FROM AUTHOR]

This study presents a thorough investigation of the novel application of graphene oxide (GO) modified with melamine formaldehyde to fabricate granular three-dimensional GO (3D-GO), followed by the introduction of UiO-66 doping (3D-GO/U) for high uranium (U) adsorption. The U(VI) adsorption isotherms revealed that 3D-GO/U-10 with 10 % UiO-66 incorporation exhibited an impressive adsorption capacity of 375.5 mg g–1 and remained high U(VI) sorption performance in wide pH range. The introduction of UiO-66 to 3D-GO (3D-GO/U-10) led to the deagglomeration of the UiO-66 particles. The in situ surface-enhanced-Raman-spectroscopy-analysis and density-functional-theory simulations showed the symmetric metal center site Zr–O 2 on UiO-66 was discovered to exhibit the highest adsorption energy (–3.21 eV) for U(VI) species due to the electrons transfer from the oxygen atom to U(VI) drives the covalent bonding between the symmetric metal center sites Zr–O 2 and U(VI) on 3D-GO/U-10. The 3D-GO/U-10 was regenerated using a 0.1 M Na 2 CO 3 /0.01 M H 2 O 2 solution and achieved up to 89.7 % U(VI) removal in the 5th cycle. The continuous flow column experiments results revealed 3D-GO/U-10 can regenerate and maintain a U(VI) removal capacity of ∼76 % for up to 4 cycles column experiments. Therefore, 3D-GO/U-10 exhibits great potential for removing U(VI) from water bodies. [Display omitted] • Novel fabrication of 3D-GO modified with melamine formaldehyde. • Introduction of UiO-66 doping for high uranium adsorption, achieving 375.5 mg/g. • Investigated dominant sorption sites of U(VI) on 3D-GO/UIO-66 via DFT and in situ SERS. • Successful regeneration of 3D-GO/UiO-66 using Na 2 CO 3 /H 2 O 2 solution in continuous experiments. • Column experiments show applicability for continuous U(VI) removal in low concentrations. [ABSTRACT FROM AUTHOR]

Herein, a sulfonated covalent organic framework (COF-SO 3 H) is prepared in situ on melamine sponge (MS) to produce MS@COF-SO 3 H as integral materials by a one-pot synthesis in water at room temperature, for facile deep removal of trace uranium-containing wastewater. The -SO 3 H on the COFs is able to form complexation with UO 2 2+ through strong coordination interactions, and MS@COF-SO 3 H is therefore highly selective for UO 2 2+ ( K d = 52603 mL g -1 ). The adsorption efficiency of MS@COF-SO 3 H-3 can reach 97.9% and 87.5% when the initial UO 2 2+ concentration is 100 and 5 μg L -1 , respectively, and the minimum residual UO 2 H make it quite promising as a highly efficient adsorbent for uranium removal. This work provides an important clue to prepare adsorbents facilely for nuclear wastewater deep treatment.2+ concentration is as low as 0.478 μg L -1 , far lower than that in previous reports. In addition, MS@COF-SO 3 H exhibits excellent durability as an adsorbent, and its adsorption efficiency for UO 2 2+ is still as high as 92.4% even after 5 cycles of recycling. The mild preparation conditions and excellent performance of MS@COF-SO 3 H make it quite promising as a highly efficient adsorbent for uranium removal. This work provides an important clue to prepare adsorbents facilely for nuclear wastewater deep treatment.

Contamination of underground water by uranium (U) and other heavy metals is a growing concern. Mesoporous silica nanoparticles (MSNs) have shown great potential as an adsorbent material for heavy metal removal. This study synthesized a novel MSN using surface-initiated atom transfer radical polymerization (SI-ATRP) and evaluated its effectiveness for removing uranium from aqueous solutions under different conditions. The particle size was reduced to 150–240 nm to enhance adsorption. Fourier transform infrared characterization and thermogravimetric analysis confirmed successful synthesis and modification. Results showed that the MSN adsorbent was highly effective in removing U, with a removal rate of 85.35% at 120 min. Temperature had a significant impact, with the highest removal rate of 96.7% achieved at 25 °C and a U concentration of 10 ppm. The highest removal rate of 91.89% was achieved at a pH of 6 and a U concentration of 50 ppm. The highest removal rate of 95.16% was achieved at 25 mg and a U concentration of 50 ppm at room temperature for 60 min. The MSNs also showed a 58.27% removal rate in a mixture solution at room temperature for 60 min. This study demonstrates the effectiveness of the MSN adsorbent for removing U under different conditions.

Several treatments for the removal of toxic heavy metals like uranium from wastewater have been developed, but none of them are sufficiently effective. Biosorption is the most feasible, eco-friendly, cost-effective, reusable technique for uranium removal. The relationship between different influencing factors in biosorption, mechanisms, competency of different biosorbents utilized, and significance of biosorption over other conventional methods have been described elaborately. The use and potentiality of genetically engineered biosorbents, modified nanoparticles for efficient biosorption are also highlighted. Among given biosorbents, Chlorella salina, Laminaria japonica, Candida utilis, chemically modified Spirulina platensis, genetically modified Deinococcus radiodurans, and Brassica juncea showed maximum biosorption capacity considering the reaction parameters. Thus, different biosorbents shows different uranium uptake potentiality due to different pH level and ionic charges present in them. Recent trends of biosorption of uranium and their present and future impact in the field of innovative and advance technology are discussed. [ABSTRACT FROM AUTHOR]

Herein, a S-scheme hollow-structured ZnO@ZnS heterojunction with Zn and S dual-vacancies was designed by a facile in - situ sulfurization and cation-exchange processes. The experimental and DFT findings demonstrate the significantly enhanced S-scheme charge transfer in the interfaces owing to the unique hollow structure and the presence of double vacancies. ZnO@ZnS shows the highest photocatalytic U(VI) removal efficiency of 96.48 % with a maximum removal capacity of 514.33 mg/g within 1 h. Various quenching experiments reveal the special involvement of h + in the reaction, and the corresponding mechanism was proposed. [Display omitted] • S-scheme hollow ZnO@ZnS heterojunction with dual surface defects was designed. • ZnO@ZnS shows 3.6- and 2.7-times enhanced U(VI) removal efficiency compared to pure ZnO and ZnS. • The DFT calculations demonstrate the significantly accelerated S-scheme carrier transfer mechanism aroused by the Zn and S vacancies. • A newly mechanism of photocatalytic U(VI) reduction was proposed. Photocatalytic reduction is a promising way to remove radioactive uranium U(VI) in wastewater. Herein, an S-scheme ZnO@ZnS heterojunction with hollow structure and dual-vacancies of Zn and S (Zn V , S V) is developed. The hollow confined space enhances light trapping ability through multiple light scattering and reflection, while the existence of vacancies extends light absorption, further enhancing the utilization of solar spectrum. Furthermore, the density function theory (DFT) calculations demonstrate that co-sharing of metal atoms at the interface and the Zn V and S V dual-vacancies induce enhanced internal electric field (IEF), leading to facilitated S-scheme charge transfer, thereby resulting in improved retention of redox potential and suppressed carrier recombination dynamics. ZnO@ZnS shows a highest U(VI) removal rate of 96.48% along with a highest U enrichment of 514.33 mg/g, which is 3.6 and 2.7-folds enhanced compared to pristine ZnO and ZnS, respectively. Through various quenching experiments, a potential new mechanism for the catalytic reduction of U(VI) is proposed. Our findings reveal the involvement of h + in the reaction, highlighting its significant catalytic role in the reduction process. Moreover, ZnO@ZnS performs excellent U(VI) extraction ability in open-air conditions without any sacrificial agents, revealing the great significance for practical applications. [ABSTRACT FROM AUTHOR]

Bioelectrochemical system (BES) is a promising technology for uranium recovery, which also enables simultaneous electricity generation. However, the bioelectrochemical recovery of uranium is hindered by its slow process due to the low reduction potential provided by microorganisms. Herein, we developed an innovative bioelectrochemical-photocatalytic system (BEPS) that combines the advantages of BES and photocatalysis, achieving enhanced uranium removal and recovery. The photogenerated electrons in BEPS possess a more negative reduction potential and stronger reduction capability than microbial electrons in BES, significantly accelerating uranium reduction and deposition on the electrode surface. Moreover, the electrons from the bioanode combine with photogenerated holes through the external circuit, effectively inhibiting the recombination of charge carriers. The BEPS significantly enhances uranium removal efficiency, kinetic, and electricity generation through a synergistic coupling mechanism between the bioanode and photocathode. Notably, the UO 2 deposited on the electrode surface exhibited a recovery efficiency of 98.21 ± 1.37%, and the regenerated electrode sustained its photoelectric response and uranium removal capabilities. Our findings highlight the potential of the BEPS as an effective technology for uranium recovery and electricity generation. [Display omitted] • Bioelectrochemical-photocatalytic system (BEPS) was developed for uranium removal. • The BEPS exhibited 5.14-fold kinetic improvement over bioelectrochemical system. • The photocathode and bioanode of BEPS synergistically enhanced uranium removal. • UO 2 deposited on the electrode can be recovered through alkaline elution. • The regenerated electrode showed excellent performance and can be reused repeatedly. [ABSTRACT FROM AUTHOR]

• Flexible hyperbranched PEI was constructed into an ultralight and elastic ordered-porous all-organic aerogel. • PEI aerogel was prepared by directional freezing and thermal crosslinking for uranium removal. • PEI aerogel showed excellent structural stability underwater and compressive properties in air. • The equilibrium and kinetic studies indicated a monolayer and chemisorption process via metal coordination. Ultralight and elastic aerogels with high capture performance offer promising prospects in pollutant treatment and resource recovery. By using directional freezing and thermal crosslinking technologies, a unique all-organic PEI-based aerogel adsorbent with exceptional mechanical stability was successfully created in this instance, which was subsequently utilized to remove uranium from aqueous solutions. The results show that compared with the honeycomb structure prepared by the traditional ice crystal technology, the PEI aerogel had a structured lamellar structure. This structure dictated the stability of aerogel in water and was directly correlated with the molecular weight of PEI and the usage of glutaraldehyde. PEI aerogel showed significant uranium-adsorption capacity in an endothermic process. The maximum adsorption capacity can reach 1262.33 mg g−1 at 298 K according to the Langmuir adsorption model. In addition, over 90 % of uranium was removed by the PEI aerogel in five cycles of adsorption and desorption process, indicating high structural stability of the PEI aerogel for practical applications. This implies that the solubility problem of hyperbranched PEI in water is effectively solved by the directional freezing method employed in this work, providing an innovative approach for the fabrication of PEI-based adsorbents. [ABSTRACT FROM AUTHOR]

Uranium (U) pollution in soil resulted by human activities is a critical environmental issue. Goethite and humic acid (HA), as predominant soil constituents, significantly influence the migration and transformation of uranium in soil, but effects of combining them together on the sequestration and immobilization of U at different mineralization condition are still rare. To simulate the ability of different combinations of HA and goethite to limit the migration of uranium (VI) in the soil environment, the humic acid-modified goethite (OPHG, TSHG) were synthesized by one-pot and two steps synthesis methods in this study. After modified by HA, the specific surface area of materials increased from 29.67 m2/g to 121.53 m2/g and 39.89 m2/g respectively. The effects of dosage, contact time, pH, initial concentration and temperature on the removal of U(VI) by goethite and modified goethite were investigated. The results showed the maximum difference of them reached 41.59% and 15.69 mg/g for reaction 60 min at pH=4.5. The equilibrium adsorption data fit to the pseudo-second-order kinetics and Langmuir models, and the maximum adsorption capacities increased from 64.63 mg/g to 92.04 mg/g. The analyses results indicated that OPHG remove U(VI) mainly through the formation of ≡ FeO UO 2 OH between Fe−O and uranyl ions, as well as the complexation of carboxyl and hydroxyl groups on HA molecules with uranium to form the HA-Goethite-U(VI) ternary complexes FeOHAUO 2. These results are benefited for understanding the effects of HA and goethite on immobilization uranium in soil and would be used to predict and remediate the polluted soil. [Display omitted] • Synthesized modified goethite in different ways to simulate the combination of humic acid and goethite in soil (OPHG, TSHG). • OPHG presented better removal efficiency than goethite and TSHG for the increased specific surface area. • The mechanism of uranium capture by modified goethite is mainly through the surface complexation reaction. [ABSTRACT FROM AUTHOR]

The removal of uranium from laboratory and environmental waters using oxidised biochar prepared from palm tree fibres has been investigated by means of batch type experiments. The effect of pH, contact time, temperature and initial uranium concentration has been studied and indicated that the adsorption follows the second order kinetic model and is an endothermic, entropy-driven process. According to the IR spectra the adsorption occurs via formation of inner-sphere complex formation between the surface carboxylic moieties and UO22+. The material has been effectively applied to remove uranium from groundwater, treated wastewater and seawater samples. [ABSTRACT FROM AUTHOR]

In the past decade, the applications of capacitive deionization have expanded to encompass resource recovery and targeted ion separation in complex solutions, besides water desalination. This comprehensive review discusses the underlying mechanisms of selective ion removal from mixed salt solutions using various electrode materials and membranes. Various mechanisms of ion selectivity are explored, considering different factors (for example, electrode pore characteristics, ion valence, operational parameters) and different chemical modifications. It also investigates ion selectivity in flow-electrode capacitive deionization. A meticulous analysis of the relevant literature from the first publications to the most recent findings allowed describing the progress in electrode and membrane preparation, theoretical knowledge, and respective roles. Furthermore, this review explores the definition and utilization of ion selectivity in different studies. Finally, a broad spectrum of ions is covered, examining the selective removal mechanisms employed for each of them. This review presents for the first time, an extensive evaluation of selective removal methods for different ions (uranium, arsenic, copper, sulfate, nitrate, phosphate, and lithium) in the capacitive deionization field. [Display omitted] • CDI applications expanded to resource recovery and targeted ion separation. • Review of the underlying mechanisms of selective ion removal considering electrode materials and membranes. • Exploring ion selectivity mechanisms: electrode pores, ion and operational characteristics, and chemical modifications. • Evaluation of diverse ions (e.g., Uranium, Arsenic, Sulfate, Nitrate, Phosphate, and Lithium) and their selective removal in CDI. [ABSTRACT FROM AUTHOR]

Uranium plant wastewater was treated in laboratory scale experiments by employing zero valent iron powder. Batch experiments conducted by the response surface methodology (RSM) proved significant decrease in concentrations of uranium due to a decrease in an oxidation-reduction potential and an increase in pH relative to an application of zero valent iron powder. Results indicated that it is effective on the removal of uranium from uranium plant wastewater with the uranium concentration of 2772.23 μg/L due to the adding of zero valent iron powder. it was found that the scope of pH is widely from 3 to 5 from the experimental data obtained in this study. The predicted model obtained from response surface methodology is in accordance with experimental results.

The removal of U(VI) ions from aqueous solutions with Bakul leaves was studied using a batch adsorption technique. The adsorption equilibrium, thermodynamics, and kinetic models were analyzed. The influence of pH, initial uranium concentration, contact time, temperature, and adsorbent dose on the uranium adsorption was estimated. The maximal uranium uptake was 86.4%. The U(VI) adsorption is well fitted using the Langmuir model and the pseudo-second-order model. Analysis of the thermodynamic functions of adsorption (ΔG°, ΔH°, ΔS°) at 303, 313 and 323 K shows that the adsorption on the surface of Bakul leaves is spontaneous and endothermic. Thus, Bakul leaves can be utilized as an economical, active, and eco-friendly adsorbent for uranium removal. [ABSTRACT FROM AUTHOR]

The adsorption technique has successfully removed toxic heavy metals from the aqueous solution over several decades. Among these metals, Uranium U(IV) is considered one of the more dangerous, toxic and radioactive elements, so there is a need to introduce cost-effective and environment-friendly biosorbents to remove U(IV) from environmental water. Though several biosorbents have been introduced, these spent tea leaves (STLs) are the most consumable product in south Asia, especially Pakistan and India. Almost every home in this region is consuming black tea and disposing it off in garbage. Herein, we introduce it as the useful and cost-effective bio absorbent for removing U(IV) from the aqueous solution. For the first time, a complete investigation and comparison of ASTLs (Acid treated spent tea leaves) for U(IV) removal from aqueous solution has been performed. The ASTL was characterized by SEM, XRD, and FT-IR. The experimental conditions were optimized and maximum adsorption of ASTL was found at pH ​= ​5.5 and 25 ​°C. The adsorption data followed Langmuir isotherm and the monolayer adsorption was 120.74 ​mg/g using only 2.0 ​g/L of ASTL. U(VI) adsorption onto ASTL was physicochemical in nature and followed both the pseudo-first and second-order kinetics. Being cheap, easily available, and with sufficient adsorption ability, ASTL can be used for the adsorption of U(VI) from wastewater ons sufficient adsorption ability. ASTL can be used to adsorption of U(VI) from wastewater on a commercial scale.

In this study, natural illite is introduced to support nanoscale zero valent iron (NZVI). The chemical composition and the physical properties of illite supported nanoscale zero valent iron (I-NZVI) are systematically investigated, and I-NZVI is found to significantly reduce the agglomeration of the NZVI particles. A comparison of the U removal capacity between I-NZVI and NZVI over various reaction times is then conducted. With an initial concentration of U at 200 μg/L, the I-NZVI removal capacity of U is as high as 3.41 mg U/g Fe, in contrast to 2.01 mg U/g Fe by NZVI at a dosage of 0.1 g/L. The initial pH of the reaction system determines the U removal capacity of I-NZVI, since it controls the speciation of U and the electron transfer processes during the reaction. Overall, based on the comprehensive understandings of the morphological change, variations in the crystalline structure, and the valence states of U and Fe, the removal mechanisms of U by I-NZVI can be concluded as the following processes: (1) the adsorption and incorporation of U(VI) onto the surface of I-NZVI, (2) the incorporation and reduction of U(V) into Fe(II), and (3) the reduction and precipitation of U(IV) with iron. [ABSTRACT FROM AUTHOR]

Uranium contamination and remediation is a very important environmental research area. Removing radioactive and toxic uranium from contaminated media requires fundamental knowledge of targets and materials. To explore the-State-of-the-Art in uranium contamination control, we employed a statistical tool called CiteSpace to visualize and statistically analyze 4203 peer-reviewed papers on uranium treatment published between 2008 and 2022. The primary content presentations of visual analysis were co-authorships, co-citations, keyword co-occurrence analysis with cluster analysis, which could offer purposeful information of research hots and trends in the field of uranium removal. The statistical analysis results indicated that studies on uranium removal have focused on adsorption of uranium from aqueous solution. From 2008 to 2022, biochar and biological treatment were firstly used to sequester uranium, then adsorption for uranium removal dominates with adsorbents of graphene oxide, primary nanofiber magnetic polymers and metal–organic frameworks (MOFs). In recent years, photocatalysts and metal–organic frameworks are expected to be two of the most popular research topics. In addition, we further highlighted the characteristics and applications of MOFs and GOs in uranium removal. Overall, a statistical review was proposed to visualize and summarize the knowledge and research trends regarding uranium treatment. [ABSTRACT FROM AUTHOR]

In this work, it was aimed to determine the potential bacterial strains that can be bioremediated of the radioactive uranium. The experimental analysis was made in gamma spectrometry. Uranyl acetate (CH 3 COO) 2 UO 2.2H 2 O was used as the radioactive material. The radioactive solutions containing bacterial strains (P. chlororaphis (3N17-10); B. licheniformis (1N17-3); L. casei (NM-25); L. plantarum (NM-10); L. brevis (NM-26); L. lactis (NM-41); L. curvatus (NM-1); L. pentosus (NM-38); L. coryniformis (NM-22) and B. subtilis (N-28)) were prepared. A high purity germanium detector with a resolution of 490 eV at 122 keV was used to measure the photon intensities emitted from the radioactive solutions. The removal percentage and adsorbed amount of the investigated samples were determined. The results showed that P. chlororaphis have got an excellent sorption capacity for uranium removal. • Uranium could be removed from aqueous systems with an efficiency of about 95%, by adsorption using bacterial strains. • The adsorption mechanism of radioactive uranium for the bacterial strains is predominantly ion exchange and ion coupling. • P. chlororaphis have got an excellent sorption capacity for uranium removal. [ABSTRACT FROM AUTHOR]

Arsenic (As) is often found naturally as the co-contaminant in the uranium (U)-contaminated area, obstructing the bioremediation process. Although the U-contaminated environment harbors microorganisms capable of interacting with U which could be exploited in bioremediation. However, they might be unable to perform with their full potential due to As toxicity. Therefore, potential in arsenic resistance and oxidation is greatly desired among the microorganisms for a continued bioremediation process. In this study, arsenic-resistant bacteria were isolated from U ore collected from Bundugurang U mine, characterized and their As oxidation and U removal potentials were determined. 16S rRNA gene sequencing and phylogenetic analysis showed the affiliation of isolated bacteria with Microbacterium, Micrococcus, Shinella, and Bacillus. Except Bacillus sp. EIKU7, Microbacterium sp. EIKU5, Shinella sp. EIKU6, and Micrococcus sp. EIKU8 were found to resist more than 400 mM As(V); however, all the isolates could survive in 8 mM As(III). The isolates were found to readily oxidize As under different culture conditions and are also resistant towards Cd, Cr, Co, Ni, and Zn. All the isolates could remove more than 350 mg U/g dry cells within 48 h which were found to be highly dependent upon the concentration of U, biomass added initially, and on the time of exposure. Ability of the isolates to grow in nitrogen-free medium indicated that they can flourish in the nutrition deprived environment. Therefore, the recovery of isolates with the potent ability to resist and oxidize As from U ore might play an important role in toxic metal bioremediation including U. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • FeS-coated Fe0 (Fes@Fe0) particles were prepared via a facile controllable method. • Both elemental and direct imaging confirmed the core-shell structure of Fes@Fe0. • FeS@Fe0 offered higher reactivity and reactive longevity than either FeS or Fe0. • FeS@Fe0 worked well at pH 5.5–9.0 and at high concentrations of bicarbonate and DOM. • FeS@Fe0 removes U(VI) through adsorption and reduction with Fe0 being main e-source. Abstract Sulfur-modified zero valent iron (S-ZVI) particles have been reported to show improved reactivity and selectivity than conventional ZVI. However, current methods for ZVI sulfidation do not fully utilize the advantages of the material, and S-ZVI has not been tested for U(VI) immobilization. In this work, we synthesized a new type of FeS-modified ZVI core-shell particles (FeS@Fe0) through a facile two-step reaction approach, and then tested for reductive sequestration of U(VI) in water. X-ray diffraction, Scanning transmission electron microscopy, and physical property analyses confirmed the formation of the core-shell structure, surface compositions and magnetic properties. Batch kinetic tests showed that FeS@Fe0 with an Fe0/FeS molar ratio of 1:1 offered the highest U(VI) reduction rate, prolonged reactive life than pristine ZVI, and the reduced uranium was most resistant to re-oxidation when exposed to oxygen. The retarded first-order kinetic model was able to adequately interpret the experimental rate data. FeS@Fe0 performed well over the pH range 5.5–9.0, with higher pH more favoring the reaction. High concentrations (5–10 mg/L) of humic acid, bicarbonate (1–5 mM) and Ca2+ (1 mM) showed only modest inhibition to the U(VI) reduction. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and extraction studies indicated that U(VI) was immobilized via both direct adsorption and reductive precipitation, where Fe0 was the main electron source, with Fe0, sorbed Fe(II) and structural Fe(II) acting as the electron donors. FeS@Fe0 may serve as an improved material for efficient immobilization of U(VI) and other redox-active contaminants in water. [ABSTRACT FROM AUTHOR]

The bacterial community of an anaerobic granular sludge associated with uranium depletion was investigated following its exposure to uranium under different initial pH conditions (pH 4.5, 5.5, and 6.5). The highest uranium removal efficiency (98.1%) was obtained for the sample with an initial pH of 6.5, which also supported the highest bacterial community richness and diversity. Venn diagrams visualized the decrease in the number of genera present in both the inoculum and the uranium-exposed biomass as the initial pH decreased from 6.5 to 4.5. Compared with the inoculum, a significant increase in the abundances of the phyla Chloroflexi and Proteobacteria was observed following uranium exposure. At initial pH conditions of 6.5 to 4.5, the proportions of the taxa Anaerolineaceae, Chryseobacterium, Acinetobacter, Pseudomonas, and Sulfurovum increased significantly, likely contributing to the observed uranium removal. Uranium exposure induced a greater level of dynamic diversification of bacterial abundances than did the initial pH difference. [ABSTRACT FROM AUTHOR]

[Display omitted] • • Highly hydrophilic phosphate functionalized silicide was obtained by one-step covalent grafting. • • The as-prepared adsorbent at ultralow dosage showed a rapid uranium removal rate. • • The as-prepared adsorbent showed an outstanding uranium adsorption capacity. • • The as-prepared adsorbent at ultralow dosage showed remarkable salt tolerance. Highly efficient removal of uranium from uranium-containing nuclear wastewater is important both for utilizing the uranium resource and protecting the environment from the hazards of uranium. However, the hypersaline environment of nuclear wastewater makes the removal of uranium a great challenge. Herein, a highly hydrophilic phosphate-functionalized silicide (VTES-PA 4) is prepared by a one-step covalent grafting method for highly efficient uranium removal from hypersaline nuclear wastewater. Impressively, the uranium removal of VTES-PA 4 reaches up to 97.4% within 7 min at an ultra-low dosage of 0.06 g/L in 12 ppm uranium solution, which outperforms most reported uranium removal materials. More importantly, the VTES-PA 4 exhibits excellent removal rates of 86.6% and 76.9% in hypersaline wastewater containing 5 M NaNO 3 and NaCl, respectively. Satisfactory uranium removal is due to the full exposure of the functional sites for binding of uranyl, endowing VTES-PA 4 with a high uranium uptake capacity of 413.2 mg/g. The adsorption mechanism has been investigated by EXAFS and XPS, which reveals that uranyl is adsorbed by coordinating with six oxygen atoms from the phosphate groups. This work enriches the study on the development of uranium adsorbents from hypersaline nuclear wastewater and can contribute to the sustainable development of the nuclear energy industry. [ABSTRACT FROM AUTHOR]

Even though uranium (U) is considered to be an essential strategic resource with vital significance to nuclear power development and climate change mitigation, U exposure to human and ecological environment has received growing concerns due to its both highly chemically toxic and radioactively hazardous property. In this study, a composite (M-BC) based on Ficus macrocarpa (banyan tree) aerial roots biochar (BC) modified by δ-MnO 2 was designed to separate U(VI) from synthetic wastewater. The results showed that the separation capacity of M-BC was 61.53 mg/g under the solid – liquid ratio of 1 g/L, which was significantly higher than that of BC (12.39 mg/g). The separation behavior of U(VI) both by BC and M-BC fitted well with Freundlich isothermal models, indicating multilayer adsorption occurring on heterogeneous surfaces. The reaction process was consistent with the pseudo-second-order kinetic model and the main rate-limiting step was particle diffusion process. It is worthy to note that the removal of U(VI) by M-BC was maintained at 94.56% even after five cycles, indicating excellent reusability and promising application potential. Multiple characterization techniques (e.g. Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray Photoelectron Spectroscopy (XPS)) uncovered that U(VI) complexation with oxygen-containing functional groups (e.g. O–C O and Mn–O) and cation exchange with protonated ≡MnOH were the dominant mechanisms for U(VI) removal. Application in real uranium wastewater treatment showed that 96% removal of U was achieved by M-BC and more than 92% of co-existing (potentially) toxic metals such as Tl, Co, Pb, Cu and Zn were simultaneously removed. The work verified a feasible candidate of banyan tree aerial roots biowaste based δ-MnO 2 -modified porous BC composites for efficient separation of U(VI) from uranium wastewater, which are beneficial to help address the dilemma between sustainability of nuclear power and subsequent hazard elimination. [Display omitted] • NaHCO 3 pretreatment and δ-MnO 2 loaded biochar (M-BC) markedly improve the U separation ability. • M-BC demonstrates excellent reproducibility for separation and recovery of U(VI). • M-BC separation mechanisms included electrostatic attraction and surface complexation. • M-BC achieved 96% U removal for high uranium radioactive wastewater. [ABSTRACT FROM AUTHOR]

The separation and enrichment of uranium from uranium containing wastewater is important for the sustainable development of nuclear energy. Therefore, there is an urgent need to develop a low-cost, readily available, simple preparation process and environmentally friendly adsorbent. In this study, potassium manganese ferrocyanide and carbon nanotube encapsulated calcium alginate beads (KMnFC/CNT@SA) for uranium adsorption was prepared by a simple method using the inexpensive natural polymer material sodium alginate and the ion exchange material potassium manganese ferricyanide as well as carbon nanotubes capable of enhancing the spatial structure. Static adsorption experiments show that the adsorption capacity of KMnFC/CNT@SA for uranium is significantly affected by pH, contact time, U(VI) concentration and temperature, but is not affected by sodium ion concentration in solution. Furthermore, desorption and cycling tests demonstrate that KMnFC/CNT@SA has good reusability, with the adsorption capacity remaining above 89.83% of the maximum adsorption capacity after 10 adsorption-desorption cycles. It is worth noting that KMnFC/CNT@SA can adsorb uranium well under acidic conditions, and is easy to solid-liquid separation and recovery. This work provides an effective strategy for the development of high-quality, inexpensive, practical and durable adsorbents for uranium extraction from acidic uranium-containing wastewater. • Solve the problem of solid-liquid separation. • Good reusability and high treatment efficiency for real acidic uranium-containing wastewater. [ABSTRACT FROM AUTHOR]

Metallic iron (Fe0) has been demonstrated as an excellent material for decentralized safe drinking water provision, wastewater treatment and environmental remediation. An open issue for all these applications is the rational material selection or quality assurance. Several methods for assessing Fe0 quality have been presented, but all of them are limited to characterizing its initial reactivity. The present study investigates H2 evolution in an acidic solution (pH 2.0) as an alternative method, while comparing achieved results to those of uranium removal in quiescent batch experiments at neutral pH values. The unique feature of the H2 evolution experiment is that quantitative H2 production ceased when the pH reached a value of 3.1. A total of twelve Fe0 specimens were tested. The volume of molecular H2 produced by 2.0 g of each Fe0 specimen in 560 mL H2SO4 (0.01 M) was monitored for 24 h. Additionally, the extent of U(VI) (0.084 mM) removal from an aqueous solution (20.0 mL) by 0.1 g of Fe0 was characterized. All U removal experiments were performed at room temperature (22 ± 2 °C) for 14 days. Results demonstrated the difficulty of comparing Fe0 specimens from different sources and confirmed that the elemental composition of Fe0 is not a stand-alone determining factor for reactivity. The time-dependent changes of H2 evolution in H2SO4 confirmed that tests in the neutral pH range just address the initial reactivity of Fe0 materials. In particular, materials initially reacting very fast would experience a decrease in reactivity in the long-term, and this aspect must be incorporated in designing novel materials and sustainable remediation systems. An idea is proposed that could enable the manufacturing of intrinsically long-term efficient Fe0 materials for targeted operations as a function of the geochemistry.

Even though uranium (U) is considered to be an essential strategic resource with vital significance to nuclear power development and climate change mitigation, U exposure to human and ecological environment has received growing concerns due to its both highly chemically toxic and radioactively hazardous property. In this study, a composite (M-BC) based on Ficus macrocarpa (banyan tree) aerial roots biochar (BC) modified by δ-MnO 2 was designed to separate U(VI) from synthetic wastewater. The results showed that the separation capacity of M-BC was 61.53 mg/g under the solid - liquid ratio of 1 g/L, which was significantly higher than that of BC (12.39 mg/g). The separation behavior of U(VI) both by BC and M-BC fitted well with Freundlich isothermal models, indicating multilayer adsorption occurring on heterogeneous surfaces. The reaction process was consistent with the pseudo-second-order kinetic model and the main rate-limiting step was particle diffusion process. It is worthy to note that the removal of U(VI) by M-BC was maintained at 94.56% even after five cycles, indicating excellent reusability and promising application potential. Multiple characterization techniques (e.g. Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray Photoelectron Spectroscopy (XPS)) uncovered that U(VI) complexation with oxygen-containing functional groups (e.g. O-CO and Mn-O) and cation exchange with protonated ≡MnOH were the dominant mechanisms for U(VI) removal. Application in real uranium wastewater treatment showed that 96% removal of U was achieved by M-BC and more than 92% of co-existing (potentially) toxic metals such as Tl, Co, Pb, Cu and Zn were simultaneously removed. The work verified a feasible candidate of banyan tree aerial roots biowaste based δ-MnO 2 -modified porous BC composites for efficient separation of U(VI) from uranium wastewater, which are beneficial to help address the dilemma between sustainability of nuclear power and subsequent hazard elimination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Electrocoagulation was used for uranium removal from Pyhäsalmi, Finland mine water. The effect of the electrode type, current density and reaction time was investigated and the removal efficiency, isotherms and kinetic data were calculated. Finally, the process was optimized with the response surface methodology (RSM) and statistically significant factors, which have an effect on the removal efficiency identified. Isotherm studies illustrated that iron–stainless steel and aluminum–stainless steel anode/cathode combinations are obeying Langmuir and Temkin isotherms, respectively. Kinetic studies showed that the iron–stainless steel and aluminum–stainless steel anode/cathode combinations are obeying first order kinetics. The interactions between current density and reaction time on the uranium removal were statistically significant for both, the aluminum–stainless steel and iron–stainless steel anode/cathode combinations. Current density was shown to be a significant parameter for iron–stainless steel and aluminum–stainless steel anode/cathode combinations. However, the reaction time was only a significant parameter in the quadratic model for the aluminum–stainless steel combination. From the analysis of variances (ANOVA), quadratic models have been employed for uranium removal, showing high coefficients of determination (R 2 ) of 0.890 and 0.903 for iron–stainless steel and aluminum–stainless steel anode/cathode combinations, respectively. The optimum conditions for current density and reaction time are 70 mA/cm 2 and 120 min, respectively, where 99.7% and 97.7% of uranium removal by iron–stainless steel and aluminum–stainless steel anode/cathode combinations could be obtained. [ABSTRACT FROM AUTHOR]

As an emerging versatile technology for separating uranium from uranium-containing wastewater (UCW), microbial fuel cell (MFC) offers a novel approach to UCW treatment. Its cathode is essential for the treatment of UCW. To thoroughly investigate the efficacy of MFC in treating UCW, investigations were conducted using MFCs with five materials (containing iron sheet (IP), stainless steel mesh (SSM), carbon cloth (CC), carbon brush (CB), and nickel foam (NF)) as cathodes. The results revealed that each MFC system performed differently in terms of carbon source degradation, uranium removal, and electricity production. In terms of carbon source degradation, CB-MFC showed the best performance. The best uranium removal method was NF-MFC, and the best electricity production method was carbon-based cathode MFC. Five MFC systems demonstrated stable performance and consistent difference over five cycles, with CC-MFC outperforming the others. Furthermore, SEM and XPS characterization of the cathode materials before and after the experiment revealed that a significant amount of U(IV) was generated during the uranium removal process, indicating that uranium ions were primarily removed by electrochemical reduction precipitation. This study confirmed that abiotic cathode MFC had a high UCW removal potential and served as a good guideline for obtaining the best cathode for MFC. [ABSTRACT FROM AUTHOR]

The removal of uranium from aqueous solutions was studied using an organic flocculant, namely, polyacrylamide (PAM) with different molecular weights in the presence of Mg(II). The influence of major parameters, such as flocculant dosage, solution pH, initial uranium concentration, dissolved organic matter, and mixing intensity, that may influence the removal efficiency of uranium were investigated. The optimum flocculation condition was 0.1-0.5 mg=L of PAM, 0.75 g=L of Mg(II) (or 1.6 g=L of MgCl2 • 6H2O), pH of 12, rapid mixing speed of 350 revolutions per minute (rpm), and slow mixing time of 1 min. Results showed that the flocculation process was fast, achieving >95% of uranium removal within <30 min at pH 12 and PAMand MgCl2 • 6H2O dosage of 0.1-0.5 ppm and 1.6 g=L, respectively. MgCl2 enhanced the removal of uranium from low radioactive wastewater by PAMflocculation. [ABSTRACT FROM AUTHOR]

In this study, the removal of uranium from aqueous solution is studied using emulsion liquid membrane (ELM) system. The ELM is made up of 2-Thenoyltrifluoroacetone (HTTA) as a carrier, kerosene as an organic diluent, HCl as a stripping solution and sorbitan monooleate (Span-80) as a surfactant for stabilizing the emulsion phase. Initially, the important parameters affecting the removal of uranium, were screened out using a fractional factorial design. Then the effect of the selected factors were studied to obtain the optimal conditions. Under the assessed conditions (pH of donor phase = 5; HTTA concentration in the membrane phase = 0.02 mol/L; emulsion/donor phase volume ratio = 0.2; uranium concentration in the donor phase <150 mg/L), the removal percentage of uranium was obtained 99.8% in less than five minutes. [ABSTRACT FROM AUTHOR]

Poly(acrylic acid-dimethylaminoethyl methacrylate) was prepared by γ-radiation-induced copolymerization at a radiation dose of 60 kGy and a dose rate of 1.25 kGy h. The resin obtained was used to remove U(VI) from simulated solution of the waste from the Fuel Manufacturing Pilot Plant (FMPP). A preliminary test of U(VI) adsorption onto the resin showed high affinity of this resin for U(VI) ions. The adsorption behavior toward the U(VI) ions was studied in relation to the contact time, pH, temperature, resin dosage, and initial concentration of metal ions. The adsorption isotherms of uranium onto the resin were described using the Langmuir and Freundlich models, with the Langmuir model being more adequate to the experimental equilibrium data. Without foreign ions, the maximum adsorption capacity of the resin for U(VI) was 105.7 mg g. X-ray fluorescence was used to evaluate the amount of U(VI) ions on the resin sample before and after the adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synergy of hydroxyl and amidoxime promotes the adsorption of uranium. • The effect of anions on uranium adsorption has been evaluated in detail. • The mechanism of fluoride inhibiting uranium adsorption is revealed. • NWF- g -PGMA-AO is suitable for removing trace uranium from nuclear effluents. 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 [UO 2 F n ]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. [ABSTRACT FROM AUTHOR]

Various types of plutonic and volcanic rocks and their alteration products from Greece (serpentinite, magnesite and andesite), have been used for sustainable removal of Uranium (U) from the acidic drainage of Kirki mine, as well as for the pH increase of the polluted solutions. In this light, this study aims at the further understanding and improvement of the ecofriendly reuse of sterile, natural raw materials (including those remaining through industrial processing and engineering testing of aggregate rocks), for remediation of acid mine drainage. The selected rocks constitute such residues of sterile materials were used as filters in experimental continuous flow devices in the form of batch-type columns, in order to investigate acidic remediation properties with special focus on U removal. The initial pH of the wastewater was 2.90 and increased after seven (7) days of experimental application and more specifically from the fourth day onwards. Uranium removal became quantitatively significant once pH reached the value of 5.09. The volcanic rocks appeared to be more effective for U removal than the plutonic ones because of microtextural differences. However, optimum U removal was mainly achieved by serpentinite: while the raw materials rich in Mg strongly reacted and remediated the pH of the drainage water waste. Furthermore, the increase of pH values due to the presence of mineral raw materials, provided increased oxidation potential which deactivated the toxic load of metals, particularly U. Consequently, batch-type serpentinite reaction with the tailing fluid caused a drop in U concentration from an initial value of 254 ppb to the one of 8 ppb, which corresponds to 97% of removal. Andesite presented the second best reactant for experimental remediation, especially when it was mixed with magnetically separated mineral fractions. Despite the fact that the proposed methodology is currently at a relatively low Technology Readiness Level (TRL), it carries the potential to become an extremely effective and low-cost alternative to conventional environmental restoration technologies. • Filters of mineral raw materials to remove uranium from acidic drainage. • Serpentinite opaque minerals are proved to be the most effective for U removal. • The proposed methodology is extremely effective and a low-cost one. • Key role for the eco-friendly U removals is mineral raw material's microstructure. [ABSTRACT FROM AUTHOR]

U(VI) species display limited adsorption onto sediment minerals and synthetic sorbents in pH <4 or pH >8 groundwater. In this work, magnetic mesoporous silica nanoparticles (MMSNs) with magnetite nanoparticle cores were functionalized with various organic molecules using post-synthetic methods. The functionalized MMSNs were characterized using N 2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), 13 C cross polarization and magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy, and powder X-ray diffraction (XRD), which indicated that mesoporous silica (MCM-41) particles of 100–200 nm formed around a core of magnetic iron oxide, and the functional groups were primarily grafted into the mesopores of ∼3.0 nm in size. The functionalized MMSNs were effective for U removal from pH 3.5 and 9.6 artificial groundwater (AGW). Functionalized MMSNs removed U from the pH 3.5 AGW by as much as 6 orders of magnitude more than unfunctionalized nanoparticles or silica and had adsorption capacities as high as 38 mg/g. They removed U from the pH 9.6 AGW as much as 4 orders of magnitude greater than silica and 2 orders of magnitude greater than the unfunctionalized nanoparticles with adsorption capacities as high as 133 mg/g. These results provide an applied solution for treating U contamination that occurs at extreme pH environments and a scientific foundation for solving critical industrial issues related to environmental stewardship and nuclear power production. [ABSTRACT FROM AUTHOR]

Activities related to nuclear industry, production of phosphoric acid and hospitals have generated considerable volumes of radioactive waste containing uranyl ions. Banana pith was characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy and was investigated as a biosorbent for uranyl ions from nitric solutions by batch experiments. Influences of adsorbent size, kinetics and equilibrium adsorption were studied. The biosorption of the uranyl ions followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Freundlich equation.

Sorption of soluble uranyl peroxo cage clusters (U60 [UO(O)(OH)] and U24Pp [(UO)(O)(PO)]) by mesoporous sorbent SBA-15 has been studied. Sorption kinetics of U60 and U24Pp are both best described by a pseudo-second-order model. However, only in the U60 sorption, intraparticle diffusion is the rate-determining step, and both pore size and pore volume of SBA-15 positively influence the U sorption capacity. Sorption isotherms of U60 and U24Pp are better fitted by the Langmuir and Freundlich isotherm models, respectively. The differences of sorption behaviors between two clusters by SBA-15 may result from differences of the sizes and terminal ligands of the clusters. [ABSTRACT FROM AUTHOR]