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Developing novel adsorbents for efficient U(VI) adsorption from wastewater is of great significance in both nuclear energy development and environmental protection. Herein, a novel functional resin (AO67/MA33-resin) with large particle size (100–200 μm) was controllably synthesized and employed for U(VI) elimination. The AO67/MA33-resin overcomes the shortcoming of small particle size of traditional adsorbents and shows strong antacid and high-temperature resistance stability and reusability. Meanwhile, the AO67/MA33-resin also exhibits excellent U(VI) removal ability including wide pH adaptability, fast adsorption kinetic, and high adsorption capacity. The adsorption mechanism was determined to involve chelation between amidoxime carboxyl functional groups and uranyl ions. A further application for U(VI) removal from real uranium mine wastewater was evaluated by dynamic column experiments. The present work indicated that the AO67/MA33-resin would be a promising adsorbent material for uranium removal from wastewater. [ABSTRACT FROM AUTHOR]

Decontamination of the toxic selenium compound, selenite (Se(IV)) and selenate (Se(VI)), from wastewater is imperative for environmental protection. Efficient approaches to remove Se(IV) and Se(VI) are in urgent needs. In this work, an accessible adsorbent Fe–OOH–bent was prepared and applied for the removal of Se(IV) and Se(VI) from wastewater. The batch experimental results demonstrate that Fe–OOH–bent exhibits high adsorption capacities of 5.01 × 10−4 and 2.28 × 10−4 mol/g for Se(IV) and Se(VI) respectively, which are higher than most of the reported bentonite based materials, especially in the case of Se(VI). Moreover, the Fe–OOH–bent displayed superior selectivity towards Se(IV) and Se(VI) even in the presence of excess competitive anions (Cl−, HCO3−, NO3−, SO42− and PO43−) and HA with concentrations of 1000 times higher than Se(IV) and Se(VI). By evaluating the adsorption ratio of Se(IV) and Se(VI), the reusability of Fe–OOH–bent was great through five adsorption-desorption cycles. For practical application, the column experiments were performed with simulated wastewater samples. The breakthrough and eluting curves of Se(IV) and Se(VI) were investigated through the columns packed with Fe–OOH–bent, and the results show that Se(IV) and Se(VI) can be successfully separated and recovered using 0.1 mol/L Na2SO4 (pH = 9.0) and 0.1 mol/L Na3PO4 (pH = 9.0), respectively. Our work provides a new approach for fractional separation as well as the recovery of Se(IV) and Se(VI) from wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • HDPy-bent with high adsorption capacity and fast kinetic for 99TcO 4 − was synthesized. • HDPy-bent displayed superior selectivity towards 99TcO 4 −. • Adsorption mechanism of anion exchange and surface precipitation was confirmed by experiments and DFT simulations. • HDPy-bent was proved to be an excellent material for 99Tc decontamination from wastewater by successful column experiments. Technetium-99 (99Tc), as one of the important high-yield fission products, poses a significant threat to the environment and human health due to its radiotoxicity, long half-life, high solubility and mobility in the environment. Thus, removal of 99TcO 4 − from radioactive wastewater is considerably imminent for waste disposal and environment conservation. In this work, Hexadecylpyridinium Chloride Monohydrate modified bentonite (HDPy-bent) was synthesised and used as an adsorbent to remove 99TcO 4 −. The adsorption behaviours of ReO 4 − as an analogue for TcO 4 − were investigated as functions of contact time, solution pH, initial concentration, and competing anions using batch techniques. It is demonstrated that the HDPy-bent showed an excellent adsorption ability for ReO 4 − at the pH range of 2–11, fast adsorption kinetic (reaching equilibrium within 3 min at room temperature), and maintains desirable ReO 4 − adsorption in the presence of concomitant anions at an excessive concentration of 500 times (Cl−, HCO 3 −, NO 3 −, CO 3 2−, SO 4 2− and PO 4 3−). As for adsorption mechanism, we propose the anion exchange process at low concentration of Re(VII) and precipitation reaction at high concentration, while the driving force of the high ReO 4 − adsorption ability is the interaction between ReO 4 − anion and pyridinium ring of HDPy+, which is confirmed by density functional theory (DFT) simulations. Additionally, DFT studies also shed light on the adsorption structure of HDPy+/ReO 4 − and the origin of adsorption selectivity. Moreover, four adsorption-desorption cycles suggest that the HDPy-bent has good durability and reusability. Furthermore, ReO 4 − can be removed completely and recovered fractionally by using the chromatography column packed with HDPy-bent from simulated groundwater samples. The work presented herein demonstrates a low-cost adsorbent which can efficiently remove 99Tc from contaminated water. [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]

[Display omitted] • A novel extractant resin DtBuCH18C6@CG-71 was successfully prepared with simple and low-cost method. • DtBuCH18C6@CG-71 exhibited remarkable separation ability of Sr(II) even in high concentration HNO 3 (3–12 mol/L). • DtBuCH18C6@CG-71 possessed great acid, irradiation and thermal resistance stability. • DtBuCH18C6@CG-71 can adeptly sequesters and recovers Sr(II) from wastewater via an automated separation system. Effective removal of radioactive 90Sr is crucial for both management of spent nuclear fuel and recovery of radioactive strontium resources, while it's still a great challenge due to the presence of high acid levels and intense radiation. Herein, a novel porous resin (DtBuCH18C6@CG-71) were synthesized by introducing 4′,4″(5″)-di- tert -butyldicyclohexano-18-crown-6 onto CG-71 resin using vacuum impregnation. The DtBuCH18C6@CG-71 resin maintains superior adsorption abilities in extreme conditions, including high acid resistance (3–12 mol/L HNO 3), substantial γ-irradiation (200 kGy 60Co), and elevated temperatures (50–100 ℃). Impressively, even when exposed to a high concentration of matrix ions (59 elemental ions), the Sr(II) adsorption ratio onto DtBuCH18C6@CG-71 resin remains near 100 % even in highly acidic condition, which performance outpaces most of commercial resins. Dynamic column tests using an automated separation system further confirmed the superior ability of DtBuCH18C6@CG-71 in term of extracting Sr(II) from wastewater. Given its impressive features, cost-effectiveness, and scalability, DtBuCH18C6@CG-71 resin holds promising potential for 90Sr disposal in nuclear wastewater. [ABSTRACT FROM AUTHOR]

99Tc primarily exists high mobility in the natural aqueous environment due to its extremely high solubility and non-complexing features, which can easily cause radioactive pollution. We herein report a general strategy for constructing a novel resin (SiPAN-PEI) with multiple positive charges nitrogen, exhibiting ultrafast adsorption kinetics (< 3 min), superior adsorption capacities (463.96 mg g−1), and excellent selectivity in the presence of excess competitive anions, which exceed those of most commercial resins. Moreover, based on impressive structure stability in extreme conditions, SiPAN-PEI can still maintain superior adsorption abilities after suffering irradiation, calcination, and immersion in strong acid. In addition, the separation performance kept excellently after five loading-washing-eluting cycles and the total adsorption ratio can still reach 97 %. Outstandingly, SiPAN-PEI can remove most of ReO 4 - from simulated nuclear wastewater through a sequential injection automatic separation system and can reduce the concentration of ReO 4 - to the maximum concentration standard set by the World Health Organization (WHO) in a short time. Leveraging density functional theory calculations and other characteristics clearly elucidated adsorption mechanism of anion-exchange between Cl- and TcO 4 -/ReO 4 -. In terms of superior adsorption property, SiPAN-PEI is demonstrated to be a pretty candidate for 99Tc elimination from wastewater. [Display omitted] • A novel resin SiPAN-PEI was successfully synthesized for selective capture of 99Tc. • SiPAN-PEI exhibited excellent adsorption ability of 99Tc in harsh conditions. • Multiple positive charge nitrogen plays a critical role in capture of 99Tc. • SiPAN-PEI demonstrated efficiency capture of 99Tc in simulated wastewater. [ABSTRACT FROM AUTHOR]

• 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]