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Visible light response PAN@Ag–Ag2O/TiO2 (PAN@AT) nanofibers with different mass ratios between Ag–Ag2O and TiO2 were synthesized via a facile electrospinning technique and pH-induced precipitation reaction. X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscope analyses manifest the formation of Ag–Ag2O/TiO2 heterojunctions, and Ag–Ag2O/TiO2 nanoparticles are evenly distributed on PAN nanofibers. The fabricated nanofibers show a highly photocatalytic performance toward As(III) oxidation under visible light, and the conversion is 92.1% after 120-min reaction at pH 5.0 in the system of PAN@AT4. Furthermore, conversion of As(III) can retain 88.6% of the original activity after repeating four cycles, indicating the good recyclability of PAN@AT4 nanofibers. Quenching experiments and electron spin resonance spectra analysis further demonstrate that the predominate active species for As(III) oxidation by PAN@AT4 are h+ and ·OH. The enhanced catalytic activity of PAN@AT4 is therefore ascribed to the formation of Ag–Ag2O/TiO2 heterojunctions on PAN surface and the efficient separation of photoinduced electron–hole pairs. This study provides a new material to oxidize reducing pollutants [such as As(III)] and also sheds light on the fabrication of recyclable photocatalysts.

The fragility of concrete-filled steel tubular (CFST) frame structures with buckling-restrained braces (BRBs) subjected to multiple earthquakes is studied in this paper. First, a fiber beam element model with rate-dependent concrete and steel material properties is developed for CFST members and, then, the effect of the strain rate on the seismic response of the CFST frame structure is investigated numerically. The influence of BRBs on the seismic response of the CFST frame structure is then comparatively analyzed. The seismic responses of the CFST frame structure with BRBs under single mainshocks and earthquake sequences are investigated, and the fragility curves are generated using probabilistic seismic demand analysis. The obtained roof displacement and inter-story drift ratio (ISDR) of the structure decreased by 10.2% and 6.9%, respectively, when obtained while considering the strain rate effect, compared with those obtained without consideration of the strain rate effect. BRBs can effectively improve the seismic performance of the CFST frame structure in that the maximum roof displacement and ISDR can be reduced by 45.1% and 43.9%, respectively. Compared with those under single mainshocks, the maximum roof displacement and ISDR of the structure with BRBs under earthquake sequences significantly increase. The fragility of the BRB structure under earthquake sequences is more severe than that under single mainshocks. Therefore, the influences of the strain rate effect and earthquake sequence should be considered to realistically evaluate the seismic fragility of CFST structures.

Mn(II) and As(III) pollutants in water pose a great threat to human health. In this study, we demonstrate that Bi2.15WO6 (BWO) can oxidize Mn(II) to amorphous manganese oxide (MnOx) under visible light for the first time, and the newly generated MnOx can further transform As(III) to As(V), achieving the purpose of treating waste by waste. After exposure to visible light, Mn(IV) (the respective content and formation rate of Mn(IV) was 2.1 mg L−1 and 9.51 μM h−1 at pH 8.9) was formed via two steps, with Mn(III) as an intermediate in the system of BWO-Mn(II). Quenching experiments revealed that O2•− and h+ play predominant roles in the visible light-induced formation of MnOx on BWO. Subsequently, oxidation of As(III) at pH 8.9 was realized by BWO-MnOx in the dark and the conversion (71.2%) was higher than that (61.7%) obtained in the synchronous photo-oxidation system of Mn(II) and As(III) by BWO. This study enriches our understanding of the intermediate in the BWO-Mn(II) system under visible light, and provides new insights for cascade oxidation of aqueous Mn(II) and As(III) under alkaline conditions.