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Because of high mobility, the immobilization of long-lived fission product 79Se (often existed as 79Se(IV) and 79Se(VI) anions) is a critical consideration in the repository of high-level radioactive waste. In this work, a Fe-OOH modified bentonite (Fe-OOH-bent) was synthesized as a potential filling material in the repository site for effective adsorption and present the migration of different species of 79Se. The adsorbent was characterized using FT-IR, XRD, XFS, zeta potential and BET to clarify its physical properties, compositions and structures. A good thermal and radiation stabilities of Fe-OOH-bent was confirmed by its stable uptake ratio for Se(IV) and Se(VI) compared to original samples. The batch experimental results show that Se(IV) and Se(VI) can be efficiently removed from aqueous by Fe-OOH-bent within 60 min with maximum adsorption capacities of 68.45 mg/g for Se(IV) and 40.47 mg/g for Se(VI) in the optimal conditions, indicating its high potential application in consideration of its simple synthesis process, low cost and high adsorption capacity in view of immobilization of 79Se. The surface species and variation of oxide state of Fe as well as Se(IV) and Se(VI) onto Fe-OOH-bent were investigated by XPS analysis. The values of relative area of Se(IV)–O and Se(VI)–O in XPS spectra followed the same tendency as their adsorption ratio with the variation of system pH, suggesting that the formation of complexes between selenium species and Fe-OOH-bent surface. [ABSTRACT FROM AUTHOR]

As a strategic resource, the safe management and recovery of uranium (U(Ⅵ)) is of great significance for environmental protection and resource recycling. To address it, the effective capture of U(Ⅵ) from wastewater is necessary but still challenging. In this work, an environmental-friendly adsorbent amidoxime and carboxyl functionalized microspheres (ACBs) were successfully prepared, characterized and evaluated for U(Ⅵ) adsorption. The ACBs exhibited outstanding adsorption abilities for U(Ⅵ) with high adsorption capacity, fast kinetics, good selectivity and excellent reusability. The U(Ⅵ) adsorption mechanism onto ACBs was synthetically investigated by various characterizations and DFT calculations, suggesting that the amidoxime and carboxyl groups coordinated with U(Ⅵ) by π and σ bonds. Further investigation in actual water samples and degradation experiments suggested that the ACBs can not only effectively remove U(Ⅵ) from wastewater, but also it can be completely degraded to achieve waste-free goals after the adsorption-desorption process. This work provides new insight into the significance of designing efficient and environmental-friendly adsorbent material for U(Ⅵ) removal from wastewater. [Display omitted] • An environmentally friendly adsorbent was prepared and used for U(VI) removal. • ACB shows powerful adsorption abilities for U(VI) under different conditions. • Adsorption mechanism was revealed as mixed coordination structures. • ACB can be degraded completely by bacteria to achieve no waste discharge. [ABSTRACT FROM AUTHOR]

[Display omitted] • U-PSresin was synthesized to use for separation and detection of U(VI). • U-PSresin shows good irradiation and thermal stability. • U-PSresin is demonstrated a highly sensitive detection efficiency of U(VI). • U-PSresin is proved to be used for continuous measurement of U(VI). It is extremely significant to monitor the radioactive uranium during the process of nuclear energy mining and disposal because of its high levels of chemical and radiological toxicity. In this work, a novel uranium plastic scintillator resin (U-PSresin) was successfully synthesized by suspension polymerization and used to rapidly enrich and determine uranium by Liquid Scintillation Counting (LSC). The U-PSresin shows excellent irradiation stability, extremely appropriate adsorption capacity of U(VI) (9.35 mg/g), which is convenient for the accurate measurement of LSC. Meanwhile, U-PSresin has a deviation of less than 5 % in adsorption and measurement repeatability and can be utilized to accurately measure more than 1 mg of natural uranium after enrichment. For different types of spiked water samples, the measurement deviation of U-PSresin is less than 15 %. This work demonstrates that U-PSresin can selectively enrich and quantitatively measure uranium in an aqueous environment, showcasing its significant potential in nuclear emergency scenarios and environmental monitoring. [ABSTRACT FROM AUTHOR]

Removal of uranium from radioactive wastewater with TPEAC. [Display omitted] • A phosphine-oxime modified adsorbent (TPEAC) was successfully prepared. • TPEAC exhibited exceptional selectivity and efficiency for adsorption of uranium. • TPEAC displayed a high recovery of 99.6% using real uranium mining wastewater. • Adsorption mechanism was elucidated through experiments and characterization. Efficient removal of uranium from radioactive wastewater is paramount for the sustainable development of nuclear energy. However, the exploitation of superior adsorbents with practical applications remains a challenge. In this work, we engineered and synthesized an adsorbent (TPEAC) enriched with phosphine-oxime, featuring a matrix composed of hydrophilic modified amidoxime functional groups. TPEAC exhibited exceptional selectivity (Multiple ion coexistence R% > 99 %) and efficiency in uranium adsorption, with a higher adsorption rate (reach equilibrium around 400 mins) and capacity (243.9 mg/g) than raw-amidoxime (133.3 mg/g) and modified-amidoxime (175.4 mg/g) materials. Moreover, it maintained robust stability and reusability even after six adsorption–desorption cycles, with removal ratio still above 95 %. In-depth mechanistic investigations through DFT and XPS elucidated that P-O (P=O) groups exhibited a stronger affinity for U(VI) compared to other functional groups, and the adsorption of TPEAC towards U(VI) primarily due to the synergistic interaction among P-O (P=O) groups, C(NH 2) = N-OH, and carboxyl groups, which significantly facilitated the effective removal of U(VI). Most prominently, TPEAC performed considerable potential in processing actual uranium mine wastewater, with its dynamic column device achieving a U(VI) recovery up to 99.6 %. This work not only furnishes an efficacious and economical solution for uranium wastewater treatment but also provides new approaches for scalable application uranium materials. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the physico-chemical, titration and Eu(III) adsorption/desorption characteristics of a purified Na-bentonite have been measured. Potentiometric titration at three ionic strengths (0.01, 0.1 and 0.5mol/L NaCl) at 25°C indicates that the point of zero charge (PZC) of the Na-bentonite increases with decreasing ionic strength. The parallel titration curves at three ionic strengths were interpreted by considering a layer site and two edge hydroxyl sites in the framework of surface complexation model. The adsorption/desorption of Eu(III) on the Na-bentonite was investigated by a batch experimental method. pH adsorption edges of Eu(III) in the absence and presence of CO2 at variable Eu(III) concentrations (6.74×10−8 and 3.33×10−6 mol/L) were collected and reasonably interpreted by a surface complexation model. Adsorption and desorption isotherms at pHs 4.04±0.05, 6.01±0.05, 6.53±0.05 and 7.46±0.05 indicate that the adsorption/desorption of Eu(III) on the Na-bentonite is reversible. The adsorption isotherms of Eu(III) were successfully reproduced by the proposed model. [Copyright &y& Elsevier]

• A highly efficient adsorbent was prepared and used for the treatment of uranium wastewater. • MXene/PAO hydrogel beads exhibit outstanding adsorption capacity under different conditions. • MXene/PAO hydrogel beads have excellent practicality coupling through columns. • Adsorption mechanism under F− conditions is the coordination of MXene and amidoxime to uranium complexes. The treatment of radioactive wastewater is crucial to ensure the safe and rapid development of nuclear energy. However, efficient disposal of uranium wastewater containing high concentrations of fluoride ions (F−) generated during uranium enrichment and conversion poses a formidable and pressing challenge. In this study, we successfully synthesized MXene/PAO hydrogel beads (MPH beads) by self-assembling two-dimensional Ti 3 C 2 T x MXene nanosheets with amidoxime through ionic cross-linking. MPH beads exhibited exceptional uranium adsorption capacity (625 mg/g), remarkable adsorption selectivity, and good reusability. Notably, MPH beads demonstrated a maximum uranium adsorption capacity of 400 mg/g in an aqueous solution containing 8000 ppm F−. Furthermore, MPH beads showed favorable F− resistance and were able to remove>95% of U(Ⅵ) even after being immersed in an extreme environment for 15 days. Additionally, MPH beads achieved a high U(Ⅵ) recovery of 98.2% from real environment water samples using dynamic column experiments, showcasing their excellent application performance. The efficient U(Ⅵ) adsorption and anti-fluoride effect were mainly attributed to the combined complexation between the C(NH 2) = N-OH, C-Ti-OH groups and U(Ⅵ), as demonstrated by experiments, characterization, and DFT calculations. Our study highlights the significant potential of MPH beads in the treatment of uranium from radioactive wastewater, especially wastewater with high concentrations of F−. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel adsorbent FeOOH@SiO 2 was successfully prepared and used for removal of Se(IV) and Se(VI). • FeOOH@SiO 2 shows powerful adsorption abilities for Se(IV) and Se(VI) in 3 mol/L HNO 3 system. • FeOOH@SiO 2 has excellent acid resistance, γ-irradiation and thermal stability. • Surface complexing process was proposed for Se(IV) and Se(VI) adsorption. Due to its high solubility, radioactivity and toxicity, the separation of selenium from spent fuel reprocessing waste and industrial wastewater has attracted much attention. In this study, a novel adsorbent FeOOH@SiO 2 with particle size of ∼100 μm was successfully prepared by loading FeOOH on micron-sized silica with emulsion methods. FeOOH@SiO 2 with good acid resistance, γ-irradiation and thermal stability exhibits excellent adsorption abilities for Se(IV) and Se(VI) including fast adsorption kinetics, great adsorption capacities (11.0 mg/g for Se(IV) and 6.04 mg/g for Se(VI)) and preferable adsorption selectivity. It is worth noting that FeOOH@SiO 2 can still remove nearly 90 % of Se(IV) and 80 % of Se(VI) even in 3 mol/L HNO 3 system. Combined with the observations from X-ray photoelectron spectroscopic characterization and surface potential measurement, the adsorption mechanism caused with electrostatic attraction and the formation of inner complexes for Se(IV), and reduction reaction and partial formation of outer complexes for Se(VI) can be deduced. After 4 adsorption–desorption cycles, FeOOH@SiO 2 still exhibits satisfactory reusability. Dynamic column experiments also demonstrated that FeOOH@SiO 2 exhibited excellent removal capabilities towards Se(IV) and Se(VI) from real water samples. The present work demonstrates that FeOOH@SiO 2 has great potential application for 79Se removal in highly acidic nuclear waste. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective removal of radioactive iodine anions from contaminated water has become a crucial task and a great challenge for waste treatment and environmental remediation. Herein, we present hexadecylpyridinium chloride monohydrate modified bentonite (HDPy-bent) for the efficient and selective removal of iodine anions (I− and IO 3 −) from contaminated water. Batch experiments showed that HDPy-bent could remove more than 95% of I− and IO 3 − within 10 min, and had maximum I− and IO 3 − adsorption capacities of 80.0 and 50.2 mg/g, respectively. Competitive experiments indicated that HDPy-bent exhibited excellent I− and IO 3 − selectivity in the excessive presence of common concomitant anions including PO 4 3−, SO 4 2−, HCO 3 −, NO 3 −, Cl− (maximum mole ratio of anions vs iodine anions was ∼50,000). An anion exchange mechanism was proposed for the selective adsorption of iodine anions. Optimal adsorption structure of HDPy+/I− (IO 3 −) at atomic level and driving forces of the I− (IO 3 −) adsorption were calculated by density functional theory (DFT) simulations. Moreover, the good durability and reusability of the HDPy-bent has been demonstrated with 5 adsorption-desorption cycles. Dynamic column experiment also demonstrated that HDPy-bent exhibited excellent removal and fractional recovery capabilities towards I− and IO 3 − from simulated groundwater and environmental water samples. In conclusion, this work presents a promising adsorbent material for the decontamination of radioactive iodine anions from wastewater on a large scale. [Display omitted] • HDPy-bent showed excellent adsorption abilities for iodide and iodate. • Anions exchange mechanism was confirmed by batch experiments and DFT simulations. • The pyridine N was the intrinsic active site of the modified bentonite. • HDPy-bent was efficient for removing radioiodine anions from wastewater. [ABSTRACT FROM AUTHOR]