Swollen-layer constructed with polyamine on the surface of nano-polyacrylonitrile cloth used for extract uranium from seawater

Study on uranium ion adsorption property of porous glass modified with amidoxime group

In this paper, we prepared three types of porous glasses (PGs) with specific surface areas of 311.60 m2/g, 277.60 m2/g, and 231.38 m2/g, respectively, via borosilicate glass phase separation. These glasses were further modified with amidoxime groups (AO) using the hydroxylamine method, yielding adsorbents named 1.5-PG-AO, 2-PG-AO, and 3-PG-AO. The adsorption performance of these adsorbents under various conditions was investigated, including sorption kinetics and adsorption mechanisms. The results reveal that the number of micropores and specific surface area of PG are significantly reduced after AO modification. All three adsorbents exhibit similar adsorption capabilities. Particularly, pH has a pronounced effect on U (VI) adsorption of PG-AO, with a maximum value at pH = 4.5. Equilibrium adsorption is achieved within 2 h, with a maximum adsorption capacity of 129 mg/g. Notably, a uranium removal rate of 99.94% is attained. Furthermore, the adsorbents show high selectivity in uranium solutions containing Na+ or K+. Moreover, the adsorbents demonstrate exceptional regeneration ability, with the removal rate remaining above 80% even after undergoing five adsorption-desorption cycles. The adsorption reaction of uranium on PG-AO involves a combination of multiple processes, with monolayer chemisorption being the dominant mechanism. Both the complex adsorption of AO and the ion exchange and physical adsorption of PG contribute to the adsorption of uranyl ions on the PG-AO adsorbents.

High mechanical property and hydrophilic electrospun poly amidoxime/poly acrylonitrile composite nanofibrous mats for extraction uranium from seawater

Seawater reserves about 4.5 billion tons of uranium, if properly extracted, could be a sustainable green energy resource for hundreds of years, alternating its limited terrestrial ore and reducing the CO2 emitted from fossil fuels. The current seawater uranium adsorbents suffer neither economically viable nor adsorption efficiency, requiring more development to harvest satisfactorily uranium from seawater. Amidoxime-based fibrous adsorbents are the most promising adsorbents of seawater uranium due to abundant chelating sites. However, they suffer from severe shrinkage and stiffness once they dry, losing porous architecture and mechanical properties. Herein, an economical and scalable two-nozzle electrospinning technology was applied to produce poly amidoxime nanofibers (PAO NFs) supported by Poly acrylonitrile nanofibers (PAN NFs) as composite PAO/PAN nanofibrous mats with high structure stability. These PAO/PAN mats, with rapid wettability and excellent mechanical strength, show promising uranium adsorption capacities of 369.8 mg/g at seawater pH level, much higher than PAO and PAN NFs. The uranium adsorption capacity of the PAO/PAN mat reached 5.16 mg/g after 7 days of circulating (10 ppm uranium) spiked natural seawater. Importantly, the composite mat maintained its fibrous structure after five adsorption-desorption cycles with more than 80 % of its adsorption capacity, confirming its recyclability and stability. Therefore, the composite PAO/PAN mat fulfills the basic requirements for effectively and economically trapping uranium from seawater, which could be a matrix for further development.

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.

Decorating UiO-66-NH2 crystals on recyclable fiber bearing polyamine and amidoxime bifunctional groups via cross-linking method with good stability for highly efficient capture of U(VI) from aqueous solution

Although polyacrylonitrile fiber (PANF) and metal-organic frameworks (MOFs) have been extensively investigated to remove U(VI) from water, their practical applications are seriously hindered by the relatively low stability of PANF in acidic solution and great difficulty of separating MOFs nanoparticles from solution, beside that, little attention is paid to the fabrication of MOFs and PANF composite materials (MPCMs) with excellent adsorption capacity for U(VI). Herein, we report the synthesis of novel MPCMs by decorating different concentrations of UiO-66-NH2 crystals onto polyamine and amidoxime groups functionalized PANF (PA-AO-PANF) through cross-linking method for U(VI) extraction. The characterization results reveal that the combination of PA-AO-PANF and UiO-66-NH2 crystals endows MPCMs with excellent separation ability, large surface area, good stability and plentiful surface functional groups, which contributes to good selectivity and enhanced adsorption performance. Consequently, the obtained UN-PA-AO-PANF-2 shows the maximum uptake capacity of 441.8 mg/g and equilibrium uptake time of 30 min towards U(VI). Besides, the U(VI) uptake ability and structure of UN-PA-AO-PANF-2 are well preserved after ten adsorption-desorption cycles. With these outstanding properties, the adsorbent has great potential for the capture of U(VI) from aqueous solutions. Importantly, this work provides a cost-effective and efficient way to construct extremely stable MPCMs hybrid fibers.

Amidoxime modified Fe3O4@TiO2 particles for antibacterial and efficient uranium extraction from seawater

Uranium extraction and recovery play a critical role in guaranteeing the sustainable nuclear energy supply and protecting the environmental safety. The ideal uranium sorbents possess high adsorption capacity, excellent selectivity and reusability, as well as outstanding antimicrobial property, which are greatly desired for the real application of uranium extraction from seawater. To address this challenge, a novel magnetic core-shell adsorbent was designed and fabricated by a facile method. The obtained amidoximed Fe₃O₄@TiO₂ particles (Fe₃O₄@TiO₂-AO) achieved equilibrium in 2 h and the maximum adsorption capacity calculated from Langmuir model is 217.0 mg/g. The adsorption kinetics followed the pseudo-second-order model. Meanwhile, the Fe₃O₄@TiO₂-AO exhibited great selectivity when competitive metal ions and anions coexisted. In addition, the magnetic Fe₃O₄@TiO₂-AO could be conveniently separated and collected by an external magnetic field, the regeneration efficiency maintained at 78.5% even after ten adsorption-desorption cycles. In natural seawater, the uranium uptake reached 87.5 μg/g in 33 days. Furthermore, the TiO₂ contained adsorbent showed effective photo induced bactericidal properties against both E. coli and S. aureus. The Fe₃O₄@TiO₂-AO with great U(VI) adsorption performance is highly promising in uranium extraction and reclamation.