Quaternized and Hyperbranched Amidoxime-Modified Ultra-High-Molecular-Weight Polyethylene Fiber for Uranium Extraction from Seawater

The most promising material for uranium extraction from saltwater is generally acknowledged to be fibrous adsorbents. An irradiation-modified anti-biofouling ultra-high-molecular-weight polyethylene (UHMWPE-g-PGAO) fibrous adsorbent with a hyperbranched structure was synthesized. It exhibited adsorption capacities of 314.8 mg-U/g-Ads in aqueous solution and 4.04 mg-U/g-Ads in simulated seawater over a 28-day period. The ultra-high-molecular-weight polyethylene (UHMWPE) fiber was functionalized by covalently linking hyperbranched polyethyleneimine (h-PEI) to facilitate the migration of uranyl ions within the fibers. Additionally, amidoxime and quaternary ammonium groups were immobilized on the fiber surface to enhance uranium affinity and provide defense against marine organisms. This three-dimensional design of amidoxime and h-PEI-modified UHMWPE fiber retained more than 91.0% of its maximum adsorption capacity after undergoing five adsorption-desorption cycles. The UHMWPE-g-PGAO adsorbent exhibits significant antibacterial activity against Escherichia coli and Staphylococcus aureus, achieving an inactivation efficiency of over 99.9%. It is proved to be an innovative fiber adsorbent for uranium extraction from seawater for its biofouling resistance, robustness, and reusability.

Anodic Electrodepositing Bioinspired Cu-BDC-NH2@Graphene Oxide Membrane for Efficient Uranium Extraction

The challenge of removing trace levels of heavy metal ions, particularly uranium, from wastewater is a critical concern in environmental management. Uranium, a key element in long-term nuclear power generation, often poses significant extraction difficulties in wastewater due to its low concentration, interference from other ions, and the complexity of aquatic ecosystems. This study introduces an anodic electrodeposited hierarchical porous 2D metal-organic framework (MOF) Cu-BDC-NH2@graphene oxide (GO) membrane for effective uranium extraction by mimicking the function of the superb-uranyl-binding protein. This membrane is characterized by its hierarchical pillared-layer structures resulting from the controlled orientation of Cu-BDC-NH2 MOFs within the laminated GO layers during the electrodeposition process. The integration of amino groups from 2D Cu-BDC-NH2 and carboxylate groups from GO enables a high affinity to uranyl ions, achieving an unprecedented uranium adsorption capacity of 1078.4 mg/g and outstanding selectivity. Our findings not only demonstrate a breakthrough in uranium extraction technology but also pave the way for advancements in water purification and sustainable energy development, proposing a practical and efficient strategy for creating orientation-tunable 2D MOFs@GO membranes tailored for high-efficiency uranium extraction.

Efficient purification of low-level uranium-containing wastewater by polyamine/amidoxime synergistically reinforced fiber

The removal and recovery of uranium [U(VI)] from organic containing wastewater has been a challenging in radioactive wastewater purification. Here, we designed a polyamine/amidoxime polyacrylonitrile fiber (PAN-AO-A) with high removal efficiency, excellent selectivity, excellent organic resistance and low cost by combining the anti-organic properties of amidoxime polyacrylonitrile fiber (PAN-AO-A) with the high adsorption capacity of polyamine polyacrylonitrile fiber, which is used to extract U(VI) from low-level uranium-containing wastewater with high ammonia nitrogen and organic content. PAN-AO-A adsorbent with high grafting rate (86.52%), high adsorption capacity (qe = 618.8 mg g-1), and strong resistance to organics and impurity interference is achieved. The adsorption rate of U(VI) in both real organic and laundry wastewater containing uranium is as high as 99.7%, and the partition coefficients (Kd) are 7.61 × 105 mL g-1 and 9.16 × 106 mL g-1, respectively. The saturated adsorption capacity of PAN-AO-A in the continuous system solution can reach up to 505.5 mg g-1, and the concentration of U(VI) in the effluent is as low as 1 μg L-1. XPS analysis and Density functional theory (DFT) studies the coordination form between U(VI) and PAN-AO-A, where the most stable structure is η2-AO(UO2)(CO3)2. The -NH-/-NH2 and -C(NH2)N-OH groups of PAN-AO-A exhibit a synergistic complex effect in the U(VI) adsorption process. PAN-AO-A is a material with profound influence and limitless potential that can be used for wastewater containing U(VI) and organic matter.

Efficient removal of uranium (VI) from water by a hyper-cross-linked polymer adsorbent modified with polyethylenimine via phosphoramidate linkers

Practical adsorbents with high efficiency are essential to effectively treating wastewater. Herein, a novel porous uranium adsorbent (PA-HCP) having a considerable amount of amine and phosphoryl groups was designed and synthesized by grafting polyethyleneimine (PEI) on a hyper-cross-linked fluorene-9-bisphenol skeleton via phosphoramidate linkers. Furthermore, it was used to treat uranium contamination in the environment. PA-HCP exhibited a large specific surface area (up to 124 m2/g) and a pore diameter of 2.5 nm. Batch uranium adsorptions on PA-HCP were investigated methodically. PA-HCP demonstrated a uranium sorption capacity of >300 mg/g in the pH range of 4-10 (C0 = 60 mg/L, T = 298.15 K), with its maximum capacity reaching 573.51 mg/g at pH = 7. The uranium sorption process obeyed the pseudo-second-order model and fitted well with the Langmuir isothermal. In the thermodynamic experiments, uranium sorption on PA-HCP was revealed to be an endothermic, spontaneous process. Even in the presence of competing metal ions, PA-HCP exhibited excellent sorption selectivity for uranium. Additionally, excellent recyclability can be achieved after six cycles. Based on FT-IR and XPS measurements, both the PO and -NH2 (and/or -NH-) groups on PA-HCP contributed to efficient uranium adsorption as a result of the strong coordination between these groups and uranium. Furthermore, the high hydrophilicity of the grafted PEI improved the dispersion of the adsorbents in water and facilitated uranium sorption. These findings suggest that PA-HCP can be used as an efficient and economical sorbent to remove U(VI) from wastewater.

Anchoring Cu-N active sites on functionalized polyacrylonitrile fibers for highly selective H2S/CO2 separation

As an essential part of clean energy, natural gas is often mixed with varying degrees of H₂S and CO₂, which poses a serious environmental hazard and reduces the fuel's calorific value. However, technology for selective H₂S removal from CO₂-containing gas streams is still not fully established. Herein, we synthesized functional polyacrylonitrile fibers with Cu-N coordination structure (PANF_EDA-Cu) by an amination-ligand reaction. The results showed that PANF_EDA-Cu exhibited a remarkable adsorption capacity (143 mg/g) for H₂S at ambient temperature, even in the presence of water vapor, and showed a good separation of H₂S/CO₂. X-ray absorption spectroscopy results confirmed the Cu-N active sites in as-prepared PANF_EDA-Cu and the formed S-Cu-N coordination structures after H₂S adsorption. The active Cu-N sites on the fiber surface and the strong interaction between highly reactive Cu atoms and S are the main reasons for the selective removal of H₂S. Additionally, a possible mechanism for the selective adsorption/removal of H₂S is proposed based on experimental and characterization results. This work will pave the way for the design of highly efficient and low-cost materials for gas separation.

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

In this study, we analyzed the removal efficiency of uranium(U(VI)) in wastewater at relatively low concentrations using strong alkaline ion exchange fiber (SAIEF). Static tests showed that the strong alkali fibers can purify U(VI) containing wastewater in a concentration range of 20-100 mg L^-1 with an optimal pH of 10.5 and contact time of 15-30 min. Adsorption and desorption cycling tests indicated that, adsorbed uranium is easily desorbed by 0.1 mol L^-1 HCl, and the fiber still maintained the original adsorption efficiency after eight cycles. According to dynamic penetration test results, the SAIEF saturation adsorption capacity was 423.9 mg g^-1, and the effluent concentration of uranium through two series columns was less than 0.05 mg L^-1, reaching the national standard for non-receiving water (GB23727-2009) SEM-EDS and FTIR analysis revealed that the functional group of SAIEF is CH₂N⁺(CH₃)₃Cl^-. Addotionally, the major forms of fiber exchange adsorption are (UO₂)₂CO₃(OH)₃^-, UO₂(CO)₃^4- and UO₂(OH)₃^-. The results indicate that the SAIEF is an excellent material for uranium removal.

Efficient extraction of U(VI) from uranium enrichment process wastewater by amine-aminophosphonate-modified polyacrylonitrile fibers

The enrichment and recovery of U(VI) from low-level radioactive wastewater in the process of uranium enrichment is important for the sustainable development of nuclear energy and environmental protection. Herein, a novel amine-aminophosphonate bifunctionalized polyacrylonitrile fiber (AAP-PAN), was prepared for the extraction of U(VI) from simulated and real uranium-containing process wastewater. The AAP-PAN fiber demonstrated a maximum adsorption capacity of 313.6 mg g^-1 at pH = 6.0 and 318 K in the batch experiments. During the dynamic column experiment, over 99.99% removal of U(VI) could be achieved by the fiber using multi-ion simulated solution and real wastewater with an excellent saturation adsorption capacity of 132.0 mg g^-1 and 72.5 mg g^-1, respectively. It also exhibited an outstanding reusability for at least 5 cycles of adsorption process. The mechanism for U(VI) removal was studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis in the assist of simulation calculation. It suggested that the amine and aminophosphonate groups can easily bind uranyl ions due to U(VI) is more likely to combine with oxygen atoms of CO and PO, respectively.

A Membrane-Supported Bifunctional Poly(amidoxime-ethyleneimine) Network for Enhanced Uranium Extraction from Seawater and Wastewater

Uranium extraction from natural seawater and wastewater are quintessential requirements to supply uninterrupted carbon-free nuclear energy and to prevent potential radiochemical and toxicological effects, respectively. Owing to the complexity and low-concentration uranium of these water samples, the design and synthesis of sorbent materials for uranium extraction with meaningful efficiencies remains a grand challenge. Herein, we reported a novel three-dimensional bifunctional network of hyperbranched poly(amidoxime-ethyleneimine) (PAO-h-PEI) using PEI as the skeleton material via cyanoethylation, crosslinking and then amidoximation. As a result of the synergistic supramolecular strategy, the PAO-h-PEI membrane achieved a remarkable adsorption capacity of 985.7 mg/g for aqueous uranium solution, which was 2.5 folds that of the monofunctional h-PEI membrane (387.6 mg/g). The PAO-h-PEI membrane also exhibited good selectivity towards uranium in the presence of various metal ions, high-content salt, and natural organic matter as well as common anions. According to the XPS and FTIR results, the utilization of amines as the second ligand enhanced uranyl binding by providing additional coordination sites or by interacting with oxime to force N-OH dissociation. The good reusability (adsorption rate of 93% after six adsorption-desorption cycles) and satisfactory adsorption performance in extracting low-concentration uranium in real seawater demonstrate its practicability.

Microwave-assisted functionalization of PAN fiber by 2-amino-5-mercapto-1,3,4-thiadiazol with high efficacy for improved and selective removal of Hg2+ from water

Mercury (Hg²⁺) contamination in water is associated with potential toxicity to human health and ecosystems. Many research studies have been ongoing to develop new materials for the remediation of Hg²⁺ pollution in water. In this study, a novel thiol- and amino-containing fibrous adsorbent was prepared by grafting 2-amino-5-mercapto-1,3,4-thiadiazol (AMTD) onto PAN fiber through a microwave-assisted method. The synthesized functional fiber was characterized by FTIR, SEM, and elemental analysis. Adsorption tests depicted that for mercury uptake, PAN_MW-AMTD fiber exhibited enhanced adsorption capacity compared with other fibrous adsorbents and selective adsorption feature under the interference of other metal ions, including Pb²⁺, Cu²⁺, Cd²⁺, and Zn²⁺. The influence of pH on the adsorption process was investigated and the effect of temperature revealed that the adsorption sorption process was endothermic and the adsorption performance of PAN_MW-AMTD was elevated with the increase of temperature. Kinetic studies of PAN_MW-AMTD fiber followed the pseudo-second-order and the adsorption isotherm of Hg²⁺ was well fitted by Sips and Langmuir equations, given the maximum adsorption amount of 332.9 mg/g. XPS results suggested that a synergetic coordination effect of sulfur and nitrogen in functional fiber with mercury took responsibility for the adsorption mechanism in the uptake process. In addition, the prepared PAN_MW-AMTD fiber could easily be regenerated with 0.1 M HCl for five times without significant reduction of mercury removal efficiency. Thus, this study will facilitate the research on novel functional material for the removal of mercury from water.

Scalable synthesis and purification of functionalized graphene nanosheets for water remediation

Microwave (MW) accelerated synthesis combined with microfiltration (MF) on commercial hollow fiber modules enables fast and scalable preparation of highly pure modified graphene oxide nanosheets. The MW-MF procedure is demonstrated on polyethylenimine (PEI) modified GO, and the so-obtained GOPEI is used for simultaneous removal of arsenic and lead from water.

Porous biochar modified with polyethyleneimine (PEI) for effective enrichment of U(VI) in aqueous solution

This study investigated the modification of moso bamboo biochar with polyethyleneimine (PEI) for the efficient enrichment of U(VI) in aqueous solution. The alkali/acid treated biochars with amine groups (PEI-alkali-biochar or PEI-acid-biochar) were characterized by SEM, BET, TGA, FTIR and XPS. The effects of contact time, U(VI) concentration, pH and ionic strength on U(VI) adsorption by PEI-alkali/acid-biochar were studied. U(VI) adsorption process on PEI-alkali/acid-biochar obeys pseudo-second-order model. Intraparticle diffusion model was used to investigate the controlled factors of the adsorption process. The fitting of Langmuir model gives the maximum adsorption capacities of 212.7 mg/g for PEI-alkali-biochar and 185.6 mg/g for PEI-acid-biochar, which are almost 9-10 times higher than that of pristine biochar (20.1 mg/g). The thermodynamic parameters illustrate that U(VI) adsorption on PEI-alkali/acid-biochar is an exothermic and spontaneous process. The FTIR and XPS analyses imply that U(VI) adsorption by PEI-alkali/acid-biochar is mainly controlled by complexation between U(VI) and amine groups. PEI-alkali/acid-biochar could be considered as a low-cost and outstanding material for U(VI) removal from radionuclide wastewater in practical application.

Hyperbranched thiourea-grafted electrospun polyacrylonitrile fibers for efficient and selective gold recovery

Research on the recovery of precious metals (including gold, Au), attracts attention of scientists worldwide. This paper reports synthesis of a novel fiber adsorbent consisting of hyperbranched thiourea-grafted electrospun polyacrylonitrile (HS-PAN) for Au(III) ion recovery. High-density functional groups of the hyperbranched structure allowed HS-PAN fibers to exhibit much higher affinity and selectivity towards Au(III) than towards Pt(IV), Cr(VI), Pb(II), Ni(II), Co(II), Fe(III), Mg(II), Cu(II) and Na(I). Au(III) adsorption proceeded according to the pseudo-second-order kinetic model and could be fitted very well using Langmuir isotherm. The maximum adsorption capacity of these fibers relative to Au(III) was 3257.3 mg/g, which is higher than the values reported in the literature for other Au(III) adsorbents. Our novel HS-PAN fibers can extract Au from real electronic waste with 99% recovery yield in just 1 h. Thus, this study demonstrates a very efficient and low-cost way to recover gold.

Adsorption capacity of kelp-like electrospun nanofibers immobilized with bayberry tannin for uranium(vi) extraction from seawater

The extraction of uranium(vi) from seawater is of paramount interest to meet the rapid expansion of global energy needs. A novel gelatin/PVA composite nanofiber band loaded with bayberry tannin (GPNB-BT) was used to extract uranium(vi) from simulated seawater in this study. It was fabricated by electrostatic spinning and crosslinking, and characterized by SEM, EDX, FTIR, and XPS. Batch experiments were carried out to investigate the adsorption of uranium(vi) onto GPNB-BT. Simultaneously, the regeneration-reuse process of the GPNB-BT was determined and illustrated here. The GPNB-BT exhibited excellent adsorption and regeneration performance, and a maximum adsorption capacity of 254.8 mg g-1 toward uranium(vi) was obtained at 298.15 K, pH = 5.5. Further, the regeneration rate for uranium did not decrease significantly after five cycles. Moreover, even at an extremely low initial concentration of 3 μg L-1 in the simulated seawater for 24 h, GPNB-BT showed an ultrahigh adsorption rate of more than 90% and adsorption capacity of 7.2 μg g-1 for uranium. The high density of adjacent phenolic hydroxyl groups and the specific surface area of GPNB-BT improved the adsorption ability of GPNB-BT for uranium. Therefore, the GPNB-BT was shown to have an application prospect for the effective extraction of uranium(vi) from seawater.

In Situ Anchoring of Pyrrhotite on Graphitic Carbon Nitride Nanosheet for Efficient Immobilization of Uranium

Enrichment of U^VI is an urgent project for nuclear energy development. Herein, magnetic graphitic carbon nitride nanosheets were successfully prepared by in situ anchoring of pyrrhotite (Fe₇ S₈ ) on the graphitic carbon nitride nanosheet (CNNS), which were used for capturing U^VI . The structural characterizations of Fe₇ S₈ /CNNS-1 indicated that the CNNS could prevent the aggregation of Fe₇ S₈ and the saturation magnetization was 4.69 emu g^-1 , which meant that it was easy to separate the adsorbent from the solution. Adsorption experiments were performed to investigate the sorption properties. The results disclosed that the sorption data conformed to the Langmuir isotherm model with the maximum adsorption capacity of 572.78 mg g^-1 at 298 K. The results of X-ray photoelectron spectroscopy (XPS) demonstrated that the main adsorption mechanism are as follows: U^VI is adsorbed on the surface of Fe₇ S₈ /CNNS-1 through surface complexation initially, then it was reduced to insoluble U^IV . Thereby, this work provided an efficient and easy to handle sorbent material for extraction of U^VI .

Halloysite nanotubes sandwiched between chitosan layers: novel bionanocomposites with multilayer structures

Multilayer chitosan/halloysite bionanocomposites with promising properties were prepared by a novel sequential casting procedure.

A novel U(vi)-imprinted graphitic carbon nitride composite for the selective and efficient removal of U(vi) from simulated seawater

A high selectivity U(vi)-imprinted g-C₃N₄/β-CD sorbent was synthesized and used for selective removal of U(vi). The interaction mechanism is mainly surface complexation and electrostatic attraction.

Efficient removal of U(vi) from simulated seawater with hyperbranched polyethylenimine (HPEI) covalently modified SiO2 coated magnetic microspheres

Hyperbranched polyethylenimine (HPEI) covalently modified SiO₂ coated magnetic microspheres were prepared for the efficient U(vi) removal from simulated seawater.