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.

MOF-derived electrochemical catalyst Cu-N/C for the enhancement of amperometric oxygen detection.

Electrochemical sensors using ionic liquids as electrolytes for oxygen detection are now getting more and more attention. Recently, an ionic liquid combined with an electrochemically active catalyst system has become popular for boosting the sensing performance of oxygen sensors. In this work, the imidazolyl-based ionic liquid 1-butyl-2,3-dimethylimidazole bis((trifluoromethyl)sulfonyl)imide [Bmmim][TFSI] is first prepared by a facile two-step method. Subsequently, a transition metal and N-codoped porous carbon oxygen reduction electrochemical catalyst Cu-N/C is synthesized by calcining the Cu-doped ZIF-8 precursor and then blending it in different ratios with the ionic liquid [Bmmim][TFSI] as composite electrolytes for oxygen detection. The composite electrolyte Cu-N/C/[Bmmim][TFSI] exhibits increased responses in cyclic voltammetry (CV) and chronoamperometry (CA) relative to that of the pure ionic liquid. Furthermore, the CV and CA data show that 6% Cu-N/C/[Bmmim][TFSI] has the optimum oxygen sensing response with an enhanced reduction peak current, a sensitivity of 0.1678 µA/[% O2] and a good linear fitting coefficient of 0.9991. In conclusion, the results confirm the success of using Cu-N/C as an electrochemical catalyst composed of the Cu-N/C/[Bmmim][TFSI] electrolyte for improving the responsivity, stability and sensitivity towards a wide range of oxygen concentrations.

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

In this study, a swelling layer was constructed on the surface of the nano-polyacrylonitrile (PAN) fiber fabric prepared by electrospinning to enrich uranium (U (VI)) adsorption from seawater. The constructed swelling layer composes of a polyethyleneimine (PEI) containing a huge amount of amino groups and imino groups with strong hydrophilicity. The molecular chain swelled in an aqueous solution by forming a swelling layer on the PAN surface. In addition, p-aminobenzenesulfonic acid (SA) was used as the side chain end group grafted on the PAN surface, the benzene ring as the side chain can hinder the rotation of the PEI chain, thereby increasing the rigidity. The increasing of the rigidity leads to stretch the conformation of the PEI molecular chain, increasing the probability of collision with U (VI), which is beneficial for adsorption. The adsorption capacity of the prepared adsorbent in the adsorption experiment reached 215.25 mg g-1, and the adsorption capacity in the 8 ppm spiked simulated seawater reached 144.5 mg g-1. The adsorption mechanism of U (VI) was analyzed by XPS. The sulfonic acid group in SA as the terminal group and amino group in the swelling layer formed a coordination structure with U (VI). The swelling layer constructed on the surface of polyacrylonitrile fibers is used to effectively extract uranium from seawater.

HFIP-Functionalized Co3 O4 Micro-Nano-Octahedra/rGO as a Double-Layer Sensing Material for Chemical Warfare Agents.

Semiconductor metal oxides (SMO)-based gas-sensing materials suffer from insufficient detection of a specific target gas. Reliable selectivity, high sensitivity, and rapid response-recovery times under various working conditions are the main requirements for optimal gas sensors. Chemical warfare agents (CWA) such as sarin are fatal inhibitors of acetylcholinesterase in the nerve system. So, sensing materials with high sensitivity and selectivity toward CWA are urgently needed. Herein, micro-nano octahedral Co3 O4 functionalized with hexafluoroisopropanol (HFIP) were deposited on a layer of reduced graphene oxide (rGO) as a double-layer sensing materials. The Co3 O4 micro-nano octahedra were synthesized by direct growth from electrospun fiber templates calcined in ambient air. The double-layer rGO/Co3 O4 -HFIP sensing materials presented high selectivity toward DMMP (sarin agent simulant, dimethyl methyl phosphonate) versus rGO/Co3 O4 and Co3 O4 sensors after the exposure to various gases owing to hydrogen bonding between the DMMP molecules and Co3 O4 -HFIP. The rGO/Co3 O4 -HFIP sensors showed high stability with a response signal around 11.8 toward 0.5 ppm DMMP at 125 °C, and more than 75 % of the initial response was maintained under a saturated humid environment (85 % relative humidity). These results prove that these double-layer inorganic-organic composite sensing materials are excellent candidates to serve as optimal gas-sensing materials.