Uranium Adsorption Performance Research Articles

“Three-dimensional environment-friendly” amino acid functionalized chitosan: Uranium adsorption performance and mechanism research

To achieve the goals of “carbon peak and carbon neutrality” and sustainable development, we propose “Three-Dimensional Environment-Friendly” materials to balance the urgent need for the development of clean energy and the reduction of secondary environmental pollution during adsorbent preparation. In this study, three novel chitosan adsorbents (CMNSC-Leu, CMNSC-Pro, CMNSC-Phe) for uranium adsorption were designed on the basis of molecular level and successfully synthesized with three different amino acids (leucine, proline, phenylalanine) through amidation reaction in an aqueous environment using a sustainable green chitosan material. The uranium adsorption capacity of the three adsorbents was evaluated by batch adsorption, selectivity and recyclability studies. The adsorption reaction conformed to the pseudo-second-order model and was a spontaneous endothermic reaction. In particular, the maximum adsorption capacity of CMNSC-Pro for uranium was 462.7 mg·g−1 at C0 = 100 ppm. In addition, CMNSC-Pro showed better selectivity and good reusability. DFT calculation and IRI diagram were applied in this work to analyze the unique structure and adsorption process of CMNSC-Pro from the perspective of structure. Uranium was adsorbed by CMNSC-Pro via coordination, electrostatic interaction, and intraparticle diffusion. This work provided a new idea for the structural design and construction of new high-efficiency biomass adsorbents.

Zwitterionic functionalized chitosan with dual-antifouling for selective uranium extraction

Uranium adsorbents deployed in natural water environments rich in microorganisms for a long time are inevitably affected. Biofouling severely reduces the uranium adsorption performance and damages the structure of the adsorbents. Therefore, antifouling performance is necessary for adsorbents that extract uranium from seawater and uranium-containing groundwater. Previously reported antifouling uranium adsorbents mainly have two types: single antibacterial or anti-adhesion, and few studies have developed dual-antifouling adsorbents that combine the two antifouling pathways. In this study, a dual-antifouling adsorbent CS-MPC with both anti-adhesion and antibacterial properties was constructed. The synergistic effect of the superhydrophilic 2-methylacryloxyethyl phosphocholine (MPC) and the natural bactericidal chitosan (CS) enabled the inhibition rate of dual-antifouling CS-MPC against various bacteria to exceed 99 %. Furthermore, the uranium adsorption capacity of CS-MPC was 579 mg/g in simulated uranium-containing groundwater and 8.28 mg/g after immersion for 42 days in real seawater. The SA/CS-MPC composite beads prepared to solve powder defects also exhibited good dual-antifouling activity and uranium adsorption properties, making them potential candidates for uranium extraction. The construction of dual-antifouling adsorbents provides a new strategy for effective biofouling control.

Multi-functional microparticles constructed by steerable phase separation process for synchronous uranium selective extraction and heat storage

Nuclear wastewater contains large amounts of uranium and waste heat, and hence synchronous uranium selective extraction and heat storage from nuclear wastewater are of prime importance. Herein, a series of distinctive dual-functional absorbents, such as P(St-VA)-1, P(St-VA)-2, P(St-VA)-3, were developed through photoinitiated interfacial polymerization via emulsion templates, using styrene and ethylene phosphate as co-monomers. The P(St-VA) has dual-functions, i.e., waste heat storage and uranium extraction. The uranium extraction feature is derived from the phosphoric acid group, while paraffin was encapsulated inside the P(St-VA). The concentration of sodium dodecyl sulfate (SDS) determines the rate and extent of phase separation between styrene and paraffin via tuning the size and stability of the emulsion, and hence the morphology and functionality of the P(St-VA). The P(St-VA) demonstrates excellent uranium adsorption performance with prominent selectivity. Furthermore, the P(St-VA) underwent multiple phase transitions between 25℃ and 70℃, displaying endothermic and exothermic behaviours and great heat storage potential. This study has provided an innovative path for the synchronous recycling of uranyl ions and waste heat from nuclear wastewater for practical applications.

Enhancing uranium adsorption performance through the introduction of a electron conjugation system on amidoximated phenyl natural bamboo strips

Commencing with the goal of establishing a more stable coordination structure for uranium, our approach drew inspiration from the alternating single and double bonds found in benzene rings and amidoxime groups. A uranium adsorption material featuring a π-electron conjugated system is devised. This system is designed by grafting 2-cyanobenzaldehyde, 3-cyanobenzaldehyde, and 4-cyanobenzaldehyde onto bamboo strips (BS) via aldol condensation and hydrolysis reactions, resulting in the creation of 2-amidoxime phenyl BS (oBS-AO), 3-amidoxime phenyl BS (mBS-AO), and 4-amidoxime phenyl BS (pBS-AO). Among these, oBS-AO exhibits not only the highest uranium adsorption performance (224.6 mg g−1 at pH = 6 and 1.3 mg g−1 in artificial simulated seawater) but also features the most robust π-electron conjugated system, as confirmed by computational and simulation data. Notably, the uranium adsorption capacity of mBS-AO is approximately 46.7 times that of vanadium in ion competition experiments simulating seawater conditions. To delve further into the adsorption mechanism, the role of electrostatic interactions and optimized simulated coordination structures is explored. It becomes evident that the primary adsorption mechanism relies on the formation of a pentacoordination structure, and the stability of this coordination structure iss directly influenced by the strength of the π-electron conjugated system. Furthermore, the double bridging effect of hydrogen bonds serves to further stabilize the coordination structure, facilitating the specific and selective adsorption of uranium.

One-step synthesis of phospho-rich, silica-enhanced chitosan aerogel for the efficient adsorption of uranium(VI)

In this study, an amorphous silica reinforced, phosphoric-crosslinked chitosan foam (P-CTS@SixOy) was prepared. The introduction of amorphous silica not only increased the affinity of the adsorbent for uranium, but also improved the stability of the material. The number of active sites of P-CTS@SixOy was increased by the introduction of phosphate groups. The material exhibited excellent uranium adsorption performance with the removal capacity and efficiency of 850.5 mg g−1 and 98.1 %, respectively. After regenerations, the morphology of P-CTS@SixOy still maintained, and the uranium adsorption efficiency remained above 90 %, manifesting the excellent cycle performance of P-CTS@SixOy. In the dynamic adsorption experiment, P-CTS@SixOy successfully concentrated the volume of uranium-containing solution, and exhibited excellent uranium adsorption performance. The analysis of kinetics, isotherms, and thermodynamics manifested that the uranium adsorption behavior of P-CTS@SixOy was a spontaneous, endothermic, monolayer chemical adsorption process. X-ray photoelectron spectroscopy, Scanning Electron Microscope, and Fourier Transform Infrared Spectrometer were used to characterized the P-CTS@SixOy before and after adsorption, which demonstrated that the main interaction mechanism between uranium and P-CTS@SixOy was the complexation. These studies indicated the huge application prospect of P-CTS@SixOy in the treatment of large-scale uranium-containing wastewater.

Enhanced uranium adsorption performance of porous MXene nanosheets

The recovery of uranium from nuclear wastewater holds considerable importance in safeguarding water resources and addressing the issue of nuclear energy scarcity. Recently, modified MXenes have emerged as a promising adsorbent for U(VI)-containing wastewater due to their abundant active sites and exceptional radiation resistance, but the incorporation of costly functional molecules is usually necessary to yield satisfactory performance. In this work, we synthesized a novel kind of nano-porous Ti3C2Tx MXene nanosheets using a simple pore-creating method with Cu2+ as catalysts, which were tested for U(VI) elimination. Impressively, the U(VI) adsorption capacity (299 mg/g) of the porous MXene nanosheets surpassed that of most previously reported modified MXene and other materials. Meanwhile, Pseudo-second-order kinetics and Freundlich models provided suitable descriptions of the adsorption process, indicating heterogeneous chemisorption occurred. Experimental and spectral analysis suggested that the enhanced U(VI) adsorption capacity of the porous MXene nanosheets primarily benefited from more active OH groups on their surface to form bidentate coordination with U(VI). This work provided a valuable concept for preparing new MXene-based adsorbent for uranium removal.

Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions

Phytic acid-modified carboxymethyl cellulose (CMC-PA) has been investigated as a promising adsorbent for the removal of uranium from aqueous solutions. The synthesis of CMC-PA involves the hydrogen bonding interaction between CMC and PA, resulting in the incorporation of PA groups onto the cellulose backbone. The hydrophilicity, reusability and adsorption capacity of the prepared CMC-PA hydrogel have improved with the increase of PA content. Moreover, the adsorption experiments were conducted by varying parameters such as pH, initial uranium concentration, and contact time. The results showed that CMC-PA exhibited excellent uranium adsorption performance, with a theoretical maximum adsorption capacity of 436 mg/g. In addition, the material exhibits excellent reusability, and the reusability improves with the increase of crosslinking density, indicating that the crosslinking structure of the polymer gel can effectively enhance the structural stability of the material. Furthermore, CMC-PA also exhibits high selective adsorption performance towards uranium ions in the presence of various competing ions. Its high adsorption capacity, reusability, and selectivity make it a promising candidate for high-performance uranium ion adsorbents.

Solar enhanced uranium extraction from seawater with the efficient strategy of MXene loaded nano-porous polyamidoxime membrane

Uranium extraction from seawater is a significant avenue for achieving sustainable energy development, but low uranium concentration and low water temperature in the ocean make it an eunormous challenge to extract uranium from seawater. To overcome these challenges, incorporating photothermal conversion components into the adsorbent holds great promise for enhancing solar-driven uranium extraction from seawater. Herein, a photothermal adsorbent PAO@MXene (PM) membrane was designed by combining 2D MXene with excellent photothermal conversion performance and polyamidoxime (PAO) with excellent uranium adsorption performance. We first fabricated a nano-porous PAO membrane via electrospinning and then prepared the PM membrane with high photothermal conversion and adsorption performance using a simple ultrasonication method. Under light condition, the adsorption capacity of PM membrane reached 452.42 mg g−1 while the adsorption capacity is 352.32 mg g−1 under dark. The adsorption capacity of light is 28.41 % higher than that of dark. Moreover, PM membrane exhibits a high uranium adsorption capacity of 2.19 mg g−1 after contact with natural seawater for a week. The results indicate that the suggested strategy can achieve solar enhanced uranium extraction from seawater through a simple method.

Efficient removal of U(VI) from wastewater by a sponge-like 3D porous architecture with hybrid electrospun nanofibers

Removal of uranium(VI) from nuclear wastewater is urgent due to the global nuclear energy exploitation. This study synthesized novel sponge-like 3D porous materials for enhanced uranium adsorption by combining electrospinning and fibrous freeze-shaping techniques. The materials possessed an organic–inorganic hybrid architecture based on the electrospun fibers of polyacrylonitrile (PAN) and SiO2. As a supporting material, the surface of fibrous SiO2 could be further functionalized by cyano groups via (3-cyanopropyl)triethoxysilane. All the cyano groups were turned into amidoxime (AO) groups to obtain a amidoxime-functionalized sponge (PAO/SiO2-AO) through the subsequent amidoximation process. The proposed sponge exhibited enhanced uranium adsorption performance with a high removal capacity of 367.12 mg/g, a large adsorption coefficient of 4.0 × 104 mL/g, and a high removal efficiency of 97.59%. The UO22+ adsorption kinetics perfectly conformed to the pseudo-second-order reaction. The sorbent also exhibited an excellent selectivity for UO22+ with other interfering metal ions.

Phytic acid modified NH2-MIL-101 via Mannich reaction for highly efficient uranium (Ⅵ) extraction from seawater

An essential part of achieving sustainable uranium resource development was the search for a suitable adsorbent capable of efficiently capturing uranium (Ⅵ) from seawater. Here, a modified metal-organic framework (PA-MIL-101) was prepared by phosphorylation of NH2-MIL-101 with phytic acid (PA). PA-MIL-101 exhibited a specific surface area of 252 m2∙g−1 and proved exceptionally adept at extracting uranium (Ⅵ) from seawater. Batch experiments were conducted to examine how environmental conditions such as pH and natural seawater affect the uranium adsorption performance of the materials. The adsorption capacity of PA-MIL-101 exhibited a remarkable performance, showcasing a substantial 41.8% increase compared to NH2-MIL-101 (the adsorption capacity increased to 416.7 mg∙g−1 at pH = 7 in 100 mg∙L−1 U(Ⅵ) solution). Due to the fast adsorption kinetics, PA-MIL-101 achieves a saturation level of 72.1% within the first 5 min. The removal rate was further elevated to 88.48% in the more intricate natural seawater. The reusability of PA-MIL-101 was demonstrated through five recycling cycles. The porous material PA-MIL-101 has abundant P=O and P–OH active sites, which can strongly complex with uranium (Ⅵ). This feature makes PA-MIL-101 perform effective in natural seawater. Therefore, PA-MIL-101 is considered as a promising supersorbent for efficient removal of uranium (Ⅵ).

Selective, rapid extraction of uranium from aqueous solution by porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite and differential charge calculation

Herein, a new porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite (PCAR) was designed and synthesized for the rapid and selective extraction of uranium resources from aqueous solution. This study showed that PCAR exhibited excellent adsorption toward uranium in a pH range of 5–9. The dynamic adsorption process aligned with the quasi-second-order kinetic model and corresponded to the chemical adsorption process. The maximum adsorption capacity was 561.28 mg·g−1 at pH 6 and 308 K. Mechanism analysis showed that the synergistic effect of the amidoxime group (−(NH2)C=N–OH), PO, and –NH2 on the PCAR surface improved the uranium adsorption performance. The differential charge density indicated that the amidoxime and phosphate groups provide lone-pair electrons for the adsorption of UO22+ and their synergistic effect improves the UO22+ adsorption performance of PCAR. The uranium distribution coefficients of PCAR and CAR are 4.6 and 2.4 times those of vanadium, respectively. These results indicate that phosphorylation can ameliorate the disadvantage of competitive vanadium adsorption of the amidoxime adsorbent. In addition, PCAR exhibits good reusability and stable adsorption capacity after five adsorption–desorption cycles. Hence, PCAR has excellent potential for uranium extraction from aqueous solution.

Effective removal of uranium (VI) using magnetic acid functionalized Fe3O4@TiO2 nanocomposite from aqueous solutions

The recovery and extraction of uranium is vital to ensure sustainability of nuclear energy production and safety of environment. Herein, we report a facile method to synthesise diglycolamic-acid-functionalized iron oxide@titanium dioxide magnetic nanocomposite (Fe3O4 @TiO2-DGA) as an efficient adsorbent for effective removal of uranium (VI) from aqueous medium. Fe3O4 @TiO2-DGA showed high uranium adsorption performance, with a sorption capacity of 371.8 mg g–1 at pH 6.0 and reached equilibrium within 40 min. The adsorption isotherm fits well with Langmuir and the kinetics follows pseudo-second-order model, respectively. The plausible mechanism of U(VI) adsorption involves the electrostatic interaction between the diglycolamic acid and hydrolysed uranium species. Thermodynamic studies revealed that the adsorption was spontaneous and exothermic in nature. The U(VI)-loaded Fe3O4 @TiO2-DGA could be conveniently separated from aqueous solutions using an external magnet, and further U(VI) is desorbed by adding dil. HCl. Fe3O4 @TiO2-DGA showed exceptional selectivity for U(VI) in presence of various coexisting metal ions and it can be effectively reused for more than 5 times with negligible change in sorption capacity. Thus, Fe3O4 @TiO2-DGA can be considered as an effective and potential sorbent for U(VI) remediation from aqueous solutions.

Effect of fiber surface functionalization on adsorption behavior of uranium from seawater desalination brine

Inspired by the easy availability and modification of fiber-like materials for water treatment and sorption applications, the functionalized natural fiber luffa cylindrica (LC) and synthetic fiber polyacrylonitrile (PAN) have been designed for the uranium adsorption. Seawater desalination brine has a significantly higher concentration of uranyl ion, so it is very meaningful to extract uranyl ions from it. In this paper, the seawater from seawater desalination plant at various treatment stages was collected to evaluate uranium adsorption performance. The effect of flocculant and scale inhibitors on uranium adsorption performance of functional fibers was also studied. The oxime/guanidine co-modified luffa cylindrica fiber (WGLC), guanidine/amidoxime co-modified polyacrylonitrile fiber (PAN-G-AO) and polyethyleneimine modified polyacrylonitrile fiber (PAN-PEI) were synthesized. PAN-G-AO showed excellent uranium capture performance with a high saturation adsorption capacity of 490.20 mg g−1 and rapid adsorption equilibrium at 15 min. Amount of uranium adsorption of three materials declined when flocculant and scale inhibitors were added. The results of adsorption experiments in various stages of seawater desalination solution for 30 days showed that adsorption materials PAN-G-AO had the largest adsorption capacity (18.6 μg g−1) in the concentrated desalinated seawater, which demonstrate promising application potential of the functionalized fiber materials for uranium adsorption from desalinated concentrated seawater.

Synthesis of core–shell magnetic nanocomposite bearing phosphonic acid ligand for uranium extraction from strong HNO3 solution

Recovery of uranium from strong acid media using magnetic nanomaterials as sorbents is vital for sustainable nuclear energy, due to their superparamagnetism and large specific surface energy. However, it remains a huge challenge to develop magnetic nanomaterials for extracting uranium from strong acid media, since magnetic nanomaterials often suffer from poor structural stability and low uranium adsorption performance in strong acid media. Herein, a novel core–shell magnetic nanocomposite Fe3O4@SiO2/P (MBA-VPA) bearing phosphonic acid was fabricated by distillation-precipitation polymerization of N, N'-methylene diacrylamide (MBA) with vinylphosphonic acid (VPA) around the surface of Fe3O4 decorated by SiO2 (Fe3O4@SiO2). By optimizing the polymerization system, high concentration of phosphonic acid with high free movement degree was led into the surface of the sorbent. Under applied conditions (c(H+) = 4 mol L−1, T = 298 K and t = 3 h), the sorbent showed a record-breaking maximum adsorption capacity (qmax) of 262.5 mg g−1 with an excellent selectivity for uranium in the presence of multi-ions. The adsorption capacity of the sorbent in strong HNO3 increased remarkably with increase of the concentration and free movement degree of phosphonic acid. By coating Fe3O4 with an inert SiO2, the sorbent exhibited excellent acidic resistance in strong HNO3. The sorbent could also be magnetically recovered within 15 s, and repeated at least six times without obvious reduction in adsorption capacity. The excellent adsorption performance in strong HNO3 media was primarily assigned to the abundant accessible PO groups, evidenced by X-ray photoelectron spectroscopy (XPS), control experiments and density functional theory (DFT). Most importantly, this work provides a new perspective for developing highly active, excellent acidic resistance, and recyclable magnetic nanomaterials for extracting uranium from strong acid media.

Preparation of biochar@chitosan-polyethyleneimine for the efficient removal of uranium from water environment

A novel chitosan-based composite with rich active sites was synthesized by uniformly dispersing biochar into the cross-linked network structure formed by chitosan and polyethyleneimine. Due to the synergistic effect of biochar (minerals) and chitosan-polyethyleneimine interpenetrating network (amino and hydroxyl), the chitosan-based composite possessed an excellent adsorption performance for uranium(VI). It could rapidly (<60 min) achieve a high adsorption efficiency (96.7 %) for uranium(VI) from water and a high static saturated adsorption capacity (633.4 mg/g), which was far superior to other chitosan-based adsorbents. Moreover, the separation for uranium(VI) on the chitosan-based composite was suitable for a variety of actual water environments and the adsorption efficiencies all exceeded 70 % in different water bodies. The soluble uranium(VI) could be completely removed by the chitosan-based composite in the continuous adsorption process, which could meet the permissible limits of the World Health Organization. In sum, the novel chitosan-based composite could overcome the bottleneck of current chitosan-based adsorption materials and become a potential adsorbent for the remediation of actual uranium(VI) contaminated wastewater.

Synthesis of hypercrosslinked calix[4]arenes anchored with Fe(III) via phosphate groups for excellent uranyl extraction from wastewater and seawater

An ideal adsorption material of uranium with not only a high adsorption capacity and high selectivity but also a broad applicability is required. In this study, a porous Fe(III) complex of phosphorylated hypercrosslinked calix[4]arenes (C4HP-Fe(III)) was synthesized. Anchoring Fe(III) via phosphate groups on phosphorylated, hypercrosslinked calix[4]arene (C4HP) significantly improved the uranium-adsorption performance, as evidenced by a 47.9 % increase in the uranium uptake (the adsorption capacity increased up to 497.6 mg·g−1 in a 60-mg·L−1 U solution). C4HP-Fe(III) is a promising adsorbent for uranyl extraction and exhibits fast capture kinetics (the adsorption capacity sharply increased in the first 30 min, which accounted for 86 % of the total amount of uranyl ions adsorbed). A study on the effect of pH on the uranium adsorption of C4HP-Fe(III) suggested that the adsorption capacity was higher than 300 mg·g−1 in the pH range of 5–10, even in a strongly acidic environment of pH 3–4, and it also had a specific adsorption capacity (≥ 168.2 mg·g−1). Furthermore, C4HP-Fe(III) possesses excellent ion selectivity for uranyl in simulated wastewater and simulated seawater, and the KdU can reach 4.1 × 103 mL·g−1 and 4.4 × 104 mL·g−1, respectively. After 6 cycles, C4HP-Fe(III) maintained its original adsorption capacity of 92.2 %. This makes it useful for wide applications and can be used for capturing uranyl ions from industrial wastewater and natural seawater. The effective extraction of uranyl was mainly attributed to the chelation of uranyl ions with both phosphate groups and active hydroxyl groups (due to the introduction of Fe3+).

Nitrogen Abundant Polyimide Covalent Organic Frameworks as Nanotraps toward Uranium Sequestration

The design and synthesis of efficient and highly selective UO22+ nanotraps still pose difficulties in the field of radionuclide removal. Herein, a stable polyimide covalent organic framework (PI-COF-6) was rationally synthesized for targeted uranium adsorption through the irreversible imidization reaction between nitrogen-rich monomer 5,5′,5″-(1,3,5-triazine-2,4,6-triyl)tris(pyridin-2-amine) (TTPA) and pyromellitic dianhydride (PMDA). The PI-COF-6 showed satisfactory uranium adsorption performance with high capacity (424.5 mg g–1), fast kinetics (98.0% removal rate in 50 min), ultrahigh selectivity among multiple metal ions, excellent stability, and outstanding recyclability. XPS characterization and DFT calculations identified that the uranium adsorption of PI-COF-6 mainly relied on the N–N–O nanotraps which were rationally constructed by pyridine nitrogen in TTPA coupling with the tertiary amine nitrogen and carbonyl oxygen in the imide ring. Moreover, the results of high-resolution U 4f XPS spectroscopy revealed that part of U(VI) was reduced into U(IV). Hence, according to the design of rational nanotraps for targeted radioactive nuclides, highly effective adsorbents for practical application (rare earth mining waste remediation) were successfully achieved.

Efficient separation of uranium(VI) from aqueous solution using magnetic Co/Al layered double oxides coated with carbon dots.

Herein, magnetic layered double oxides coated with carbon dots (MLCs) were synthesized through introducing sodium dodecylbenzene sulfonate and FeCl2 into Co/Al LDH for capturing uranium from aqueous solution. When the molar ratio of Co to Al was 4 : 1, the MLC composite possessed the strongest affinity to uranium(VI) in solution with short equilibrium time (<160 min), high adsorption efficiency (94.31%) and large removal capacity (513.85 mg g-1). The adsorption behavior of MLCs for uranium(VI) was well fitted with Langmuir and pseudo-second-order models, suggesting that the monolayer chemical adsorption was the rate-limiting step. Besides, MLC-3 could be reused by using 0.15 mol L-1 ethylene diamine tetraacetic acid as an eluent and the removal percentage still remained at a high level (>83.3%) after 5 adsorption/desorption cycles. Redox reaction, chemical complexation and electrostatic attraction were proved to play significant roles in uranium(VI) separation. Therefore, MLC-3 could be used as a potential adsorbent in uranium(VI)-containing wastewater treatment due to its excellent adsorption performance for uranium(VI).

Experimental study on efficient electrocatalytic reduction of U(VI) at Amine-Amidoxime bifunctional graphite felt electrode

• The TETA-PAO/GF electrode material was prepared by a simple and green method. • The TETA-PAO/GF electrode material exhibits excellent electrocatalytic reduction of U(VI) under electric field conditions. • The TETA-PAO/GF electrode material has good selectivity and reusability. • The TETA-PAO/GF electrode material can electrocatalytically reduce U(VI) in real seawater under electric field conditions. The amidoxime-based material is one of the effective materials for adsorbing uranium. The electrocatalysis can be used as an effective strategy for separating uranium. In this study, conductive graphite felt was used as substrate, amination-amidoxime modified polyacrylonitrile (PAN) graphite felt was prepared by heterogeneous method. With the successful synthesis of the material with bifunctional groups, the bifunctional modified PAN graphite felt (TETA-PAO/GF) had good uranium adsorption performance by the way of electrocatalysis technology. It was characterized by SEM, FT-IR, XPS, XRD, ICP-MS, etc. The adsorption capacity of the electrode material to uranium reached 1 142 mgU·g -1 in unsaturated state in 1 000 mg·L -1 spiked seawater. In real seawater adsorption experiment, 90.08% uranium was extracted from 16 L seawater. Ultimately, the assessment of the reusability and ion selectivity of TETA-PAO/GF revealed that it has a certain use value for uranium extraction from seawater.

Effects of chain conformation on uranium adsorption performance of amidoxime adsorbents

The amidoxime group has received widespread attention owing to its high affinity for uranium. Since this property was discovered, various amidoxime-based adsorbents have been developed for uranium adsorption. However, the effect of chain conformation on the uranium adsorption performance (in terms of adsorption capacity, stability, selectivity, etc.) of amidoxime adsorbents has rarely been studied. Herein, three amidoxime-based adsorbents with different chain conformations (linear, multi-armed, and rigid) were constructed via tert-butyl hydroperoxide-initiated surface graft polymerization by incorporating different monomer structures. Adsorption experiments revealed that the linear structure of P-E-PAO exhibited the highest adsorption capacity owing to the highest monomer-grafting ratio; the multi-arm structure of P-E-PMGO was affected by pH and ionic strength because of the most cyclic imide dioxime structure; and the rigid structure of P-E-PEBO showed the highest selectivity owing to the most open-chain amidoxime structure. These findings are expected to have strong implications in the optimization of adsorption material designs.