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.

Experimental characterization of temperature sensitive dyes for laser induced fluorescence thermometry.

Laser induced fluorescence (LIF) is a non-intrusive optical technique that uses fluorescent dyes to measure whole-field fluid scalars such as temperature, concentration, pH, etc. LIF measurements' accuracy is strongly influenced by the fluorescent dye's behavior under different experimental conditions. In particular, ratiometric LIF thermometry accuracy depends on the correct selection of fluorescent dyes mixtures. Therefore, a thorough characterizations of fluorescent dyes is needed to obtain optimal mixtures and suitable optical configurations for given experimental conditions. This work presents the experimental characterization of fluorescein-27 (FL27) and rhodamine-B (RhB) mixtures to determine suitable aqueous solutions for ratiometric LIF thermometry. The mixtures' fluorescence emission intensity was measured with a spectrofluorometer, and the influence of concentration ratio (C(RhB)/C(FL27)), temperature, excitation wavelength (λ(ext)), and pH were analyzed. The results show that the temperature dependence of FL27 emission intensity changed from a negative to a positive value as the excitation wavelength increased. The temperature sensitivity (4.0% per °C) of RhB and FL27 mixture under 532 nm excitation wavelength was found to be higher than that of the commonly used mixture of RhB and Rh110 (2.0% per °C) at the same excitation wavelength. While the emission intensities of the dyes are sensitive to pH value, the temperature dependence is unaffected. The influence of concentration ratio on temperature sensitivity depends on both the detected bands of the emitted spectrum and the temperature; the concentration ratio should be selected based on the measured temperature scope. A new multicolor method or advanced two color method with high temperature sensitivity (6.0% or 10.0% per °C) is presented. This technique was specially developed to improve whole-field temperature measurements.