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During the amidoximation process, transformation details of poly(acrylonitrile) (PAN) to poly(amidoxime) (PAO) is critical for optimizing amidoximation conditions, which determine the physicochemical properties and adsorption capabilities of PAO-based materials. Although the optimization of amidoximation conditions can be reported in the literature, a detailed research on the transformation is still missing. Herein, the effect of the amidoximation conditions (i.e. temperature, time, and NH2OH concentration) on the physicochemical properties and adsorption capabilities of PAO was studied in detail. The results showed that the extent of amidoximation reaction increased with increasing temperature, time, and NH2OH concentration. However, a considerably high temperature (>60 °C) and a considerably long time (>3 h) could result in the degradation and decomposition of PAO's surface topologies and functional groups, and then decrease its adsorption capability for U(VI). The optimal amidoximation condition was 3 h, 60 °C and 50 g L−1 NH2OH. At this condition, the PAO obtained presented the highest adsorption capability for U(VI) under experimental conditions. These results provide pivotal information on the transformation of PAO-based materials during the amidoximation process.

This study synthesized nFe0 on the substrate of porous organic polymer (POM) which was prepared by glutaraldehyde and melamine. The POM-nFe0 composites were characterized by scanning electron microscopy, Brunner–Emmet–Teller, Fourier transform infrared spectrum, thermogravimetric analysis, powder X-ray diffraction, and X-ray photoelectron spectroscopy. The introduction of POM contributed to enhance the stability of U(IV) nanoparticles which is liable to be oxidized to mobile U(VI) under aerobic condition. According to the batch experiment, the maximum U(VI) removal capacity of POM-nFe0 was 230 mg/g, which shows great potential in wastewater treatment.

Herein, we report a convenient method for the preparation of a self-assembled supramolecular material containing phosphoric acid (PM) choosing phytic acid and melamine as the two organic building blocks. The PM was chosen as an adsorbent for the first time for the fast adsorption and recovery of U(VI) from acidic aqueous media. The batch adsorption experiments showed that PM-9 possesses a very fast adsorption kinetic with the adsorption process for U(VI) from acidic water reaching equilibrium within 2 min. A considerable adsorption capacity of 1034.9 mg/g and an excellent selectivity 58.6% toward U(VI) in acidic aqueous solution were obtained. The adsorption capacity in dynamic column experiment was determined to be 251.0 mg g–1, with the recovery efficiency as high as 99.4% when using Na2CO3 as a stripping agent. The adsorption mechanism was probed by FT–IR, XRD, SEM, XRF, and XPS, implying the double bond oxygen atom of phosphoric acid and the nitrogen atom of amino group complexes with uranyl ions in t...

Uranium extraction from seawater provides the potential for a long-term green fuel supply for nuclear energy. However, the successful extraction of uranium from seawater is challenging because of the low uranium concentrations in seawater. Herein, we report poly(acrylamidoxime-co-acrylic acid) brush (PAO-co-AA)-based adsorbents that can highly efficiently extract and recover uranium from seawater. The PAO-co-AA-grafted fibers were fabricated by grafting of acrylonitrile and tert-butyl acrylate on poly(vinyl chloride) fibers via ARGET–ATRP method, followed by amidoximation and hydrolysis. The ARGET–ATRP method allowed for the synthesis of controllable polymer brushes with various grafting degrees (665–5908%) and thicknesses (15.1–56.3 µm) by varying the monomer concentrations during grafting. The uranium adsorption capacities of the grafted fibers were strongly affected by the grafting degree but independent of the surface area. The uranium adsorption capacities increased from 79 to 370 mg g−1 as the grafting degree increased from 665 to 3749%. The high adsorption performance can be attributed to the stretching of the polymer chain in the polymer brushes, which allows for full access of uranium ion to uranium-binding groups. The adsorbents demonstrated high uranium adsorption capacity of 5.4 mg g−1 using natural seawater in a batch adsorption mode after contact of 27 days, which is higher than that of most other adsorbents. The findings provide a new insight into the relationship between the structure and adsorption property and foreshadow the potential to use polymer brush-based adsorbents for uranium extraction from seawater.

Uranium recovery from seawater offers a promising route for producing scalable and sustainable nuclear energy because the world’s oceans contain hundreds of times more uranium than lands. A current adsorption method presents limitations including low extraction capacity and slow extraction kinetics, making realistic implementation impractical. Here we develop an electrochemical extraction approach that demonstrates high extraction capacity and fast extraction kinetics in uranium recovery. In the electrochemical approach, chitosan-functionalized electrodes were used to offer surface specific binding to uranyl ions; voltages were then supplied to attract the ions to the electrode and induce electrodeposition of uranyl ions to form charge-neutral uranium species. The electrodeposition approach demonstrated nearly 8 times higher uranium extraction capacities and 3 times faster extraction rates than the current adsorption method in uranium-spiked seawater. Because of the excellent uranium extraction performanc...

With the vigorous development of nuclear power and the shortage of terrestrial uranium resources, the extraction uranium from seawater is extremely attractive for human development. Herein, we first report ZIF-8 in-situ growth on amidoximerized polyacrylonitrile (PAO) porous materials. The porous material is a small sphere with certain mechanical strength synthesized by solvent-induced phase separation method. Because ZIF-8 nanocrystals are well-formed and evenly distributed within the PAO beads, ZIF-8/PAO has a high specific surface area (386 m2 g-1) and rich pore structure. At adsorption experiment, the highest adsorption capacity of ZIF-8/PAO reached 803 mg g-1 at pH = 4. Furthermore, competitive adsorption experiment and simulated seawater test was studied. The selectivity for uranium was excellent (Kd = 1.7 × 105 mL g-1) and uranium adsorption rate reached 99% at 3 ug L-1. XPS analysis shows that U(VI) is chelated by imidazole-N atoms and amidoxime groups in ZIF-8/PAO. Therefore, ZIF-8/PAO can be considered a highly promising adsorbent for uranium extraction from wastewater and seawater.

Polymer brushes exhibit functionalities useful for a large number of applications. Often these functionalities only emerge when the polymer brushes have a desired thickness. Here, a significant breakthrough is achieved in the synthesis of ultra-thick polymer brushes using polymer initiators in the approach of surface-initiated atom transfer radical polymerization, yielding polymer brushes with a controllable thickness up to 15.1 µm. This is reportedly the thickest polymer brush ever synthesized. This approach is applicable for several monomers such as acrylonitrile, methyl acrylate, and styrene, and for other types of polymer substrates such as fibers.

Silica antireflection coatings from sol-gel processes are of great importance in optical areas because of their capability to reduce light reflection and hence to increase transmission. However, it retained a challenge to enhance the mechanical durability of the sol-gel antireflection coatings. One option is to introduce strong chemical bonding between neighboring silica nanoparticles in the coatings. Here, we demonstrate that ammonia treatment is an effective approach to enhance the mechanical durability of the silica antireflection coatings. The coatings after ammonia treatment exhibited excellent mechanical properties, with tensile hardness of 4.4 GPa, pencil hardness of 4H, and good abrasion resistance, which is noticeably better than the coatings without ammonia treatment. The ammonia treatment did not impair the optical property of the coatings. The coatings after ammonia treatment remained their good transmission, with peak transmittance as high as 99.8%. Mechanism analysis suggests that the enhancement of the mechanical durability is likely due to the condensation of silanol groups between the neighboring silica nanoparticles under ammonia catalysis. The ammonia treatment provides a promising alternative to current approaches for improving the mechanical durability of the sol-gel silica coatings.

Self-cleaning antireflection coatings have potential applications in outdoor conditions and have been the subject of intense study. However, self-cleaning antireflection coatings are commonly prepared via grafting of small hydrophobic molecules, which are susceptible to detachment from the coatings due to hydrolysis, leading to considerable degradation of the self-cleaning functionality in practical applications. Here, we create fluoropolymer brush grafted silica antireflection coatings that demonstrate long-term self-cleaning performance. Fluoropolymer brush grafted silica nanoparticles were synthesized via surface initiated atom transfer radical polymerization and then coated on glass substrates to form antireflection coatings. The brush grafted coatings exhibited excellent transmission, with nearly 100% transmittance at a desired wavelength. The fluoropolymer brushes rendered the coatings hydrophobic, with water contact angle of 122°. Owing to their hydrophobicity, the brush grafted coatings exhibited excellent self-cleaning functionality. A notable advantage of the brush grafted coatings was their stable self-cleaning functionality. The brush grafted coatings remained their hydrophobicity after immersion in acidic solution, with water contact angle being constant at 122°, which were more stable than the small molecule modified hydrophobic coatings. This work opens a new avenue to create highly stable self-cleaning antireflection coatings that will find applications in harsh conditions.

Antireflective coatings with adjustable transmittance and high laser-induced damage threshold (LIDT) have been prepared by the deposition of magnesium fluoride (MgF2) nanoparticles on fused silica substrates. The peak transmittance of the coatings is 99.98%, mainly due to the low refractive index caused by the introduction of porosity between MgF2 nanoparticles. With varying the coating thickness, the optimized antireflective performance of the coatings at any wavelength between 300 and 1100 nm can be achieved. The effect of the particle size on the antireflective properties of the coatings has been also investigated. The coatings prepared from small particles exhibit higher transmittance at short wavelengths than do the coatings prepared from large particles. The LIDTs of the coatings at 351 nm, 527 nm and 1053 nm are 25 J/cm2, 34 J/cm2 and 63 J/cm2, respectively. The high LIDT of the coatings can be mainly attributed to the large band gap of MgF2. The antireflective coatings may be potentially applied in the high-powered lasers.

Nanostructured magnesium fluoride (MgF 2 ) antireflective films with ultra-high laser induced damage thresholds (LIDTs) have been prepared through dip coating of ~10 nm MgF 2 nanoparticles on fused silica substrates. The films increase transmittance from 93.0% for bare substrates to 99.98% for coated substrates. The LIDTs of the nanostructured MgF 2 films reach as high as 25 J/cm 2 at 351 nm, 34 J/cm 2 at 527 nm and 63 J/cm 2 at 1053 nm, respectively. The LIDTs of the nanostructured MgF 2 films is higher than that of dense MgF 2 films and sol–gel derived silica films. Such high LIDTs of the nanostructured MgF 2 films may be attributed to the large band gap and the quantum size effect of the MgF 2 nanoparticles. These nanostructured MgF 2 films will be utilized as antireflective films used in high-peak-power laser system.

Amidoxime-based adsorbents are widely studied as the main adsorbent in the recovery of uranium from seawater. However, the adsorption rate and loading capacity of such adsorbents should be further improved due to the economic viability consideration. In this paper, polyvinyl alcohol functionalized with amidoxime (PVA-g-AO) has been prepared as a new adsorbent for uranium (VI) adsorption from aqueous solution. The physicochemical properties of PVA-g-AO were investigated using infrared spectroscopy (IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results showed that the ligand monomers were successfully grafted onto the matrixes. The XRD and XPS analysis showed that uranium was adsorbed in metal ionic form rather than in crystal form. Uranyl (U (VI)) adsorption properties onto PVA-g-AO were evaluated. The adsorption of U (VI) by PVA-g-AO was fast, with an equilibrium time of less than 50 min. Additionally the maximum adsorption capacity reached 42.84 mg/g at pH 4.0.

Silica antireflective films modified by polyvinyl butyral (PVB) were deposited on fused silica substrates by sol–gel process. The effects of PVB on the microstructure and laser damage threshold (LIDT) of films were investigated. The results of the nano particle analyzer and scanning probe microscope revealed that PVB molecules surrounded silica particles and controlled the particle growth, which resulted in a stable sol with uniformly distributed silica particles. Therefore, the films deposited from these modified sols possessed more uniform microstructures than the films without PVB. The adhesive-resistance test indicated that the strength of the modified silica films increased due to the bond reaction between PVB molecules and silica particles. The introduction of PVB into silica sols had also increased the LIDT of films. The LIDT of films increased from 30.0 J/cm 2 to 40.1 J/cm 2 after 1.0 wt.% PVB was added. The increase in LIDT was attributed to the increased strength and uniform microstructures of films as an effect of the PVB modification.

The surface-initiated atom transfer radical polymerization (ATRP) was used to prepare poly-divinylbenzene(DVB)–vinylbenzylchloride(VBC)graft–amidoxime (AO) (PDVA) for the efficient removal of uranyl(VI) from aqueous solution with micro-concentration (mass fraction ranging from 0.01 to 1 %) and trace-concentration (mass fraction less than 0.01 %). By varying the ratio of DVB and VBC in ATRP process, it was to adjust the microstructure. The adsorption properties of adsorbents with micropore, mesopore and nanopore were studied and the maximum adsorption capacities of uranyl(VI) on the PDVA was 89.80, 115.40 and 84.30 mg/g in micro-concentration, 1.61, 1.90 and 1.52 mg/g in trace-concentration respectively.

Hollow polyphenylsilsesquioxane microspheres were fabricated under mild conditions from a mixture of water and phenyltriethoxysilane (PTES) with ammonia as catalyst. The pH value and the temperatur...