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Manganese tetravalent oxide (MnO2), a superstar Faradic electrode material, has been investigated extensively for capacitive desalination, enabling higher salt adsorption capacity compared to the great majority of carbonous electrodes. However, few works paid attention on the relationship between the valences of manganese oxide and their desalination performance. For the first time, we prepared the spindle-like manganese oxides/carbon composites with divalent (MnO@C), trivalent (Mn2O3@C) and divalent/trivalent (Mn3O4@C) manganese by pyrolysis of manganese carbonate precursor under different condition, respectively. The electrochemical behavior in three-electrode system and electrosorption performance obtained in hybrid membrane capacitive deionization (HMCDI) cells assembled with capacitive carbon electrodes were systematically evaluated, respectively. High salt adsorption capacity (as large as 31.3, 22.2, and 18.9 mg·g−1) and corresponding average salt adsorption rates (0.83, 0.53, and 1.71 mg·g−1min−1) were achieved in 500 mg·L−1 NaCl solution for MnO@C, Mn2O3@C, and Mn3O4@C, respectively. During fifteen electrosorption-desorption cycles, ex-situ water contact angle and morphology comparison analysis demonstrated the superior cycling durability of the manganese oxide electrodes and subtle difference between their surface redox. Furthermore, density functional theory (DFT) was also conducted to elaborate the disparity among the valence states of manganese (+2, +3 and +2/+3) for in-depth understanding. This work introduced manganese oxide with various valences to blaze new trails for developing novel Faradic electrode materials with high-efficiency desalination performance by valence engineering.

The Acoustic Black Hole (ABH) effect is the phenomenon in which the wave velocity gradually decreases to zero when the bending wave propagates in wedge-like structures, such that no reflection occurs. This means that in the ideal scenario, flexural wave not reflects and the energy is totally captured at the tip of the wedge structure. ABH structures have great potential in the fields of vibration control and energy harvesting due to this phenomenon. In this paper, the semi-analytical method is adopted to establish the dynamical model of the one-dimensional cylindrical beam with ABH feature and arbitrary boundary condition. In order to investigate the effect of energy aggregating, the proportion of the kinetic or stain energy trapped in the arbitrary vicinity of the edge, as compared to that of the whole beam is defined and analyzed in detail. The main purpose of this paper is to analyze the different energy concentration effect between the tapered cylindrical beam and the wedge-like rectangular beam and hence to provide guidance for their applications in vibration control and energy harvesting. Numerical results show that considerable kinetic and strain energy are collected either in the tapered cylindrical beam or in the wedge-like rectangular beam. However, the energy density at the tip of the tapered cylindrical beam is obviously larger than that at the edge of the wedge-like rectangular beam. This means that vibration attenuation is increased when the same amount of viscoelastic material is adhered to the tip of the tapered cylindrical beams compared to the case of the wedge-like rectangular beams. Moreover, changing the excitation location on the tapered beam can also enhance energy concentration for different frequency bands. The theoretical model developed and new findings in this paper give rise to innovative applications of ABH beam structures in engineering and open new horizons to explore in the future.

More discrete and active nano-scale zero-valent iron (NZVI) particles were obtained by assembling them on the surface of carbonized fungi (F) in this study. NZVI/F composites can totally remove 0.25 mmol/L U(VI) in 0.5 h at pH 6.5. Both sorption and reductive precipitation of U(VI) resulted in the high removal. Preliminary evidence showed that the influence of ions (Na+, K+, Ca2+, Mg2+, and CO32−) on NZVI/F composites reactivity varied with system pH. Our findings could provide an essential start in the treatment of water containing U(VI) and multiply coexistent ions, and open the doorways for the application of NZVI/F composites.

In this study, zero-valent iron-aluminum (NZVI-Al) bimetallic particles formed from Al(0) core and nano-scale Fe(0) shell were synthesized for highly effective U(VI) removal. The NZVI-Al bimetallic particles were characterized by SEM-EDS, FT-IR, XRD, and XPS. Batch experiment demonstrated that the reactivity of NZVI-Al bimetal was greatly improved relative to single zero-valent iron or aluminum. The enhanced U(VI) removal capacity up to 575 mg/g (but not to saturation at pH 5.0 and T = 30 °C) could be attributed to stronger reduction ability of NZVI-Al from the galvanic cell effect. XRD and XPS results indicated that U(VI) was immobilized via the reduction as UO2(s) and surface sorption as U(VI). The NZVI-Al bimetallic particles are promising for further testing to achieve the rapid and effective removal of U(VI) from polluted water.