Trace Zinc-Preload for Enhancement of Uranium Adsorption Performance and Antifouling Property of AO-Functionalized UHMWPE Fiber

GFN-xTB-Based Computations Provide Comprehensive Insights into Emulsion Radiation-Induced Graft Polymerization

In this article, a deep insight into emulsion radiation-induced graft polymerization (RIGP) was obtained by computing explicit solvation free energies, conformational entropy, monomer radius and dipole moments with the state-of-the-art Conformer-Rotamer Ensemble Sampling Tool (CREST) package primarily at semiempirical GFN-xTB level. By leveraging the robustness of the CREST package, above parameters provided dynamic nature of methacrylate monomers with the consideration of realistic emulsion conditions. With the chemical and physical importance of the above results, CREST-determined explanatory variables sufficiently led to the building of the prediction models for the RIGP of methacrylate monomers. The machine learning model building resulted in effective reactivity predictions and unveiled important factors for the radiation-induced graft polymerization in a chemically interpretable fashion.

Intercalation of salicylaldoxime into layered double hydroxide: ultrafast and highly selective uptake of uranium from different water systems via versatile binding modes

We report the first example of MgAl layered double hydroxide intercalated with salicylaldoxime (SA-LDH) which exhibits excellent uranium (U(VI)) capture performance. In U(VI) aqueous solutions, the SA-LDH shows a tremendous maximum U(VI) sorption capacity (q_m^U) of 502 mg·g^-1, surpassing most known sorbents. For the aqueous solution with an initial U(VI) concentration (C₀^U) of ∼ 10 ppm, ≥99.99 % uptake is achieved in a wide pH range of 3-10. At C₀^U ∼ 20 ppm, >99 % uptake is reached within only 5 min, and pseudo-second-order kinetics rate constant (k₂) of 44.9 g·mg^-1·min^-1 reaches the record value, placing the SA-LDH amongst the fastest U adsorbing materials reported to date. In contaminated seawater with 35 ppm of U while highly concentrated metal ions of Na⁺, Mg²⁺, Ca²⁺, and K⁺, the SA-LDH still displays exceptionally high selectivity and ultrafast extraction for UO₂²⁺, giving >95 % uptake of U(VI) within 5 min, and the k₂ value of 0.308 g·mg^-1·min^-1 for seawater surpasses most reported values for aqueous solutions. Versatile binding modes toward U by SA-LDH, including complexation (UO₂²⁺ with SA^- and/or CO₃^2-), ion exchange and precipitation, contribute to the preferable uptake of U at different concentrations. X-ray absorption fine structure (XAFS) analyses demonstrate that one uranyl ion (UO₂²⁺) binds to two SA^- anions and two H₂O molecules forming 8-coordinated configuration. The U coordinates with O atom of the phenolic hydroxyl group and N atom of the -CN-O^- group of SA^-, forming a stable six-membered ring motif, which endows the fast and robust capture of U. The wonderful uranium trapping ability makes the SA-LDH among the best adsorbent used for uranium extraction from various solution systems including seawater.

Uranium extraction from seawater: material design, emerging technologies and marine engineering

Uranium extraction from seawater (UES), a potential approach to securing the long-term uranium supply and sustainability of nuclear energy, has experienced significant progress in the past decade. Promising adsorbents with record-high capacities have been developed by diverse innovative synthetic strategies, and scale-up marine field tests have been put forward by several countries. However, significant challenges remain in terms of the adsorbents' properties in complex marine environments, deployment methods, and the economic viability of current UES systems. This review presents an up-to-date overview of the latest advancements in the UES field, highlighting new insights into the mechanistic basis of UES and the methodologies towards the function-oriented development of uranium adsorbents with high adsorption capacity, selectivity, biofouling resistance, and durability. A distinctive emphasis is placed on emerging electrochemical and photochemical strategies that have been employed to develop efficient UES systems. The most recent achievements in marine tests by the major countries are summarized. Challenges and perspectives related to the fundamental, technical, and engineering aspects of UES are discussed. This review is envisaged to inspire innovative ideas and bring technical solutions towards the development of technically and economically viable UES systems.

Polyamidoxime grafting on ultrahigh-strength cellulose-based jute fabrics for effectively extracting uranium from seawater

Ultrahigh-strength cellulose-based jute fabric (jute–TMC–PAO) for the highly effective extraction of uranium from seawater.

Extremely stable amidoxime functionalized covalent organic frameworks for uranium extraction from seawater with high efficiency and selectivity

Uranium extraction from seawater is of strategic significance for nuclear power generation. Amidoxime-based functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency. Nevertheless, balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium. Herein, a polyarylether-based covalent organic framework functionalized with open-chain amidoxime (COF-HHTF-AO) was synthesized with remarkable chemical stability and excellent crystallinity. Impressively, the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g, which is 1.61 times higher than that for vanadium. Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime. Combining enhanced adsorption capacity, excellent selectivity and ultrahigh stability, COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.

Polyguanidine-modified adsorbent to enhance marine applicability for uranium recovery from seawater

The marine applicability of adsorbents intended for recovering uranium from seawater is crucial. For such applicability, the materials must exhibit anti-biofouling properties, seawater pH adaptability (pH~8), and salt tolerance. Extracting uranium from seawater is a long-term project; hence, biofouling, high salt concentrations, and weak alkaline environments negatively affect the adsorption of uranium and damage the recovered materials. Most studies on the extraction of uranium from seawater focus on increasing the adsorption capacity of the employed adsorbent, while its marine applicability is neglected. In the present study, three types of guanidine polymer (GP)-modified acrylic fibers were prepared to investigate the impact of the introduced structure on the marine applicability of the fibers. After screening, the introduction of polyhexamethylene biguanidine (PHMB) is observed to produce PAO-PHMB-A, characterized by excellent marine applicability. The enhanced properties include high antimicrobial activity (10⁹ CFU/mL, 99.71%), good salt tolerance, and optimal adsorption at a pH of 8. Owing to the synergistic effect of its functional groups, the PAO-PHMB-A material exhibits excellent adsorption performance (525.89 mg/g), as well as high selectivity and durability. More importantly, long-term marine tests revealed that PAO-PHMB-A shows a remarkable uranium adsorption capacity (30 d, 3.19 mg/g) and excellent antibacterial activity. Considering its excellent marine applicability and good adsorption performance, the PAO-PHMB-A material developed in this work could serve as a potential adsorbent for engineering applications associated with uranium recovery from seawater.

Reusable fibrous adsorbent prepared via Co-radiation induced graft polymerization for iodine adsorption

Volatile iodine released from nuclear power plant reactors is radiological hazard to environment and human's health because of their high fission yield and environmental mobility. The complexity of nuclear waste management motivated the development of solid-phase adsorbents. Herein, co-radiation induced graft polymerization (CRIGP) was employed in the graft polymerization of N-vinyl-2-pyrrolidone (NVP) onto polyethylene-coated polypropylene skin-core (PE/PP) fibers using electron beam (EB) irradiation. This work provides a one-step green synthetic approach to prepare iodine fibrous adsorbents without any chemical initiators or large amount of organic solvent. The original and modified PE/PP fibers were characterized by fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and scanning electron microscopy (SEM) to demonstrate the grafting of NVP onto the PE/PP fibers. The capacity of iodine absorbed by the PE/PP-g-PNVP fibers was 1237.8 mg/g after 180 min. Meanwhile, absorbents can be regenerated efficiently by two different means of ethanol elution and heating at 120 °C, respectively. Within 10 min, 94.17% and 90.12% of the iodine can be released from the PE/PP-g-PNVP fibers with these two methods, respectively. The adsorbent exhibited a long service life of at least ten adsorption-desorption cycles, suggesting that PE/PP-g-PNVP fibers might be a promising adsorbent for volatile iodine adsorption from fission products in nuclear power plant reactors.

Synthesis of Fibrous Metal Adsorbent with a Piperazinyl-Dithiocarbamate Group by Radiation-Induced Grafting and Its Performance

A fibrous grafted metal adsorbent with a piperazinyl-dithiocarbamate (PZ-DTC) group was synthesized by radiation-induced emulsion grafting of glycidyl methacrylate onto a polyethylene-coated polypropylene nonwoven fabric (PE/PP-NF) and subsequent three-step chemical modifications consisting of amination with N-(tert-butoxycarbonyl)piperazine (N-Boc-piperazine, NBPZ), deprotection of the Boc group with HCl, and dithiocarbamation with carbon disulfide (CS2). By using the NBPZ reagent in the amination step, the self-cross-linking of piperazine (PZ) could be completely suppressed, unlike using the PZ reagent. Consequently, the PZ-DTC group density of the fibrous grafted metal adsorbent synthesized through NBPZ attained 2.122 mmol-PZ-DTC/g-adsorbent, which was approximately 6 times higher than that of the metal adsorbent synthesized through PZ. The fibrous grafted metal adsorbent with the PZ-DTC group selectively adsorbed heavy metal ions over light metal ions. Furthermore, it exhibited high adsorption capacity, particularly for Cu2+. The Cu2+ adsorption capacity was determined to be 1.903 mmol-Cu2+/g-adsorbent by a batchwise adsorption test using a single-metal-ion aqueous solution at pH 6. The order of metal ion selectivity of the fibrous grafted metal adsorbent with the PZ-DTC group was Na+ < Mg2+, Ca2+, Co2+, Cd2+ < Pb2+ ≪ Cu2+, and Co2+ ≈ Ni2+ < Zn2+ ≪ Cu2+. In addition, the fibrous grafted metal adsorbent with the PZ-DTC group did not lose its metal adsorption function even under highly alkaline conditions (pH 15). It could recover Cu2+ efficiently and selectively from a high-concentration Na+ aqueous solution at this pH. The Cu2+ adsorption capacity of the fibrous grafted metal adsorbent with the PZ-DTC group was 0.754 mmol-Cu2+/g-adsorbent under a highly alkaline condition, a 10 M NaOH aqueous solution at pH 15. This value was approximately 2.4 times higher than that of the other grafted adsorbent with an amine-type functional group.

A novel ion-imprinted amidoxime-functionalized UHMWPE fiber based on radiation-induced crosslinking for selective adsorption of uranium

A novel uranium-imprinted adsorbent (AO-Imp fiber) was prepared by radiation-induced crosslinking of amidoxime-functionalized ultra-high molecular weight polyethylene fiber (AO fiber). The porous structure was characterized by scanning electron microscopy (SEM) and positron annihilation lifetime (PAL) spectroscopy after ion imprinting. This ion-imprinted fiber exhibited enhanced adsorption selectivity for uranium in the form of both UO2 2- and [UO2(CO3)3]4- in batch experiments. Compared with AO fiber, the adsorption capacity of the AO-Imp(250) fiber for uranium increased from 0.36 mg g-1 to 1.00 mg g-1 in simulated seawater and from 5.02 mg g-1 to 12.03 mg g-1 in simulated acid effluent, while its adsorption capacities for other co-existing metal ions were particularly low. This study provides an approach to prepare ion-imprinted adsorbents without introducing crosslinking reagents, which may be a promising method for uranium extraction.