Kai Lv

Characterizations of Nb-doped WO3 nanomaterials and their enhanced photocatalytic performance

In this paper, Nb-doped WO3 nanowires were successfully prepared using a low-temperature, hydrothermal method. The physicochemical properties of pristine and Nb-doped WO3 were determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy (UV-vis). The photocatalytic properties of those Nb-doped WO3 nanomaterials are evaluated on the basis of their ability to degrade methylene blue (MB) in an aqueous solution under simulated sunlight irradiation. It is demonstrated that the pristine nanowires tend to aggregate, whereas the energy band gap of those nanomaterials narrows as more niobium ions are doped. The photocatalytic experimental results indicated that the Nb-doped WO3 exhibited superior photocatalytic activities to that of the undoped WO3. The Nb-doped WO3 nanowires synthesized with an Nb/W molar ratio of 0.03 possessed the most effective photocatalytic activity among the tested samples.

Characterization of Li-doped WO3 nanowires and their enhanced electrocatalytic oxidation of ascorbic acid

Li-doped WO3 nanowires have been hydrothermally prepared and characterized mainly via spectroscopic methods. Both the hexagonal structure distortion and morphology evolution induced by Li doping reveal a lattice expansion of about 0.07 A. Also, the residence of oxygen vacancy and the enlargement of external surface areas positively correlate with the narrowing of energy band. Subsequently, the electrocatalytic oxidation of ascorbic acid using a Li-doped WO3 film-coated electrode performs a 13% and 21% negative shift of the oxidation overpotential compared with a WO3 film-coated electrode and a bare glassy carbon electrode, respectively. A preliminary mechanism has been proposed on the basis of relevant model analyses.

Pyrochlore Ta-doped antimony oxide as a novel adsorbent for efficient strontium removal

Hydrous antimony oxide Sb2O5·4H2O with a pyrochlore structure is an ion exchanger that is selective toward Sr2+ in mild solutions. The present study aims to improve the Sr2+ adsorption capacity of antimony oxide. Cubic pyrochlore non-doped and Ta-doped antimony oxide nanoparticles were prepared by a hydrothermal method. The particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 gas sorption, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Incorporation of Ta5+ into the sorbent led to an expansion of the pyrochlore structure, and increases in the surface hydroxyl group content and surface area of the sorbent, consequently improving the Sr2+ adsorption capacity considerably. A satisfactory correlation coefficient and a relatively low normalized standard deviation of the fit of the experimental data using the Freundlich model demonstrate that Sr2+ adsorption onto Ta-doped antimony oxide proceeds via a multilayer chemical adsorption process. Thermodynamic studies were conducted under different reaction temperatures. The results indicate that Sr2+ adsorption onto Ta-doped antimony oxide is an endothermic and a spontaneous process. Under the current experimental conditions, the maximal Sr2+ adsorption capacity of 26.37 mg g−1 was obtained at pH 4.

The Hydrolytic Stability and Degradation Mechanism of a Hierarchically Porous Metal Alkylphosphonate Framework

To aid the design of a hierarchically porous unconventional metal-phosphonate framework (HP-UMPF) for practical radioanalytical separation, a systematic investigation of the hydrolytic stability of bulk phase against acidic corrosion has been carried out for an archetypical HP-UMPF. Bulk dissolution results suggest that aqueous acidity has a more paramount effect on incongruent leaching than the temperature, and the kinetic stability reaches equilibrium by way of an accumulation of a partial leached species on the corrosion conduits. A variation of particle morphology, hierarchical porosity and backbone composition upon corrosion reveals that they are hydrolytically resilient without suffering any great degradation of porous texture, although large aggregates crack into sporadic fractures while the nucleophilic attack of inorganic layers cause the leaching of tin and phosphorus. The remaining selectivity of these HP-UMPFs is dictated by a balance between the elimination of free phosphonate and the exposure of confined phosphonates, thus allowing a real-time tailor of radionuclide sequestration. Moreover, a plausible degradation mechanism has been proposed for the triple progressive dissolution of three-level hierarchical porous structures to elucidate resultant reactivity. These HP-UMPFs are compared with benchmark metal-organic frameworks (MOFs) to obtain a rough grading of hydrolytic stability and two feasible approaches are suggested for enhancing their hydrolytic stability that are intended for real-life separation protocols.

Capillary electrophoresis coupled with in‐column fiber‐optic laser‐induced fluorescence detection for the rapid separation of neodymium

In this study, in‐column fiber‐optic (ICFO) laser‐induced fluorescence (LIF) detection technique is coupled with capillary electrophoresis (CE) for the rapid separation of neodymium for the first time. The effects of buffer concentration, buffer pH, and separation voltage on the CE behaviors, including electrophoretic efficiency and detection sensitivity, are investigated in detail. Under the optimal condition determined in this study (15 mM borate buffer, pH 10.50, separation voltage 24 kV), neodymium could be separated effectively from the neighboring lanthanides (praseodymium and samarium) within several minutes, and the limit of detection for neodymium is estimated to be at the ppt level. The ICFO‐LIF‐CE system assembled in this study exhibits unique performance characteristics such as low cost and flexibility. Meanwhile, the separation efficiency and detection sensitivity of the assembled CE system are comparable to or somewhat better than those obtained in the previous traditional CE systems, indicating the potential of the assembled CE system for practical applications in the fields of spent nuclear fuel analysis, nuclear waste disposal/treatment, and nuclear forensics.