Sun Jialin,Dai Jingtao,Liu Rui,Yang Xiaowei,Chen Jian
To improve the visible-light catalytic performance of TiO 2 for practical application, Ag/AgBr modified TiO 2 was fabricated in ionic liquid–water medium via a facile hydrothermal reduction method. Imidacloprid (IMI) was employed as the target pollutant to evaluate the critical impacts on the catalytic activity of as-prepared Ag/AgBr/TiO 2 , where the factors relating to the catalyst (composition, dosage, recycle and reuse) and solution chemistry (pH and concentration, simulated wastewater samples and floodwater of rice paddy field) were studied. The results suggested that benefitting from visible-light sensitive Ag/AgBr and high specific surface area TiO 2 , Ag/AgBr/TiO 2 exhibits superior visible-light photocatalytic activity and stability to Ag/AgBr and TiO 2 . The quenching tests with various scavengers indicate that · O 2 − and h + , and · O 2 − and · OH may be the key roles in IMI photo-degradation on Ag/AgBr and on Ag/AgBr/TiO 2 , respectively. Thus, the photocatalytic performance of Ag/AgBr/TiO 2 differs from that of Ag/AgBr. Furthermore, the contribution of such active species is clarified for quantitative mechanisms study. The photo-degradation conducted in the simulated wastewater and the floodwater of rice paddy field proves favorable anti-interference capacity of Ag/AgBr/TiO 2 . The tests conducted on real wastewater sample verified that Ag/AgBr/TiO 2 can mineralize IMI promptly and almost completely.
Sun Jialin,Huang Dejia,Liu Rui,Dai Jingtao,Chen Jian
To improve the visible-light photocatalytic performance of TiO 2 for practical application, Ag/AgBr modified TiO 2 was fabricated in ionic liquid–water medium via a facile hydrothermal-reduction method. The visible-light catalytic activity of as-prepared Ag/AgBr/TiO 2 was measured using tetracycline (TC) as the target pollutant. Characterizations by various techniques (SEM–EDS, XRD, XPS and DRS) and the quenching experiments with scavengers for possible active species (h + , • O 2 − and ·OH) were executed to probe the mechanism underlying the photocatalytic performance. Critical impacts from the catalyst and solution chemistry were evaluated in the mediums of TC solution, simulated wastewater and real wastewater sample. The results suggested that: (1) benefitting from the visible-light sensitive Ag/AgBr and high specific surface area TiO 2 , Ag/AgBr/TiO 2 exhibits fair stability and remarkable visible-light photocatalytic activity; (2) under optimized conditions, Ag/AgBr/TiO 2 provides higher visible-light catalytic activity than Ag/AgBr and TiO 2 ; (3) the coexisting inorganic ions with high concentration in the simulated wastewater sample depress TC photo-degradation, and the impacts varies with the species of inorganic ions; (4) COD removal rate about 65.5% in real wastewater sample proves that Ag/AgBr/TiO 2 can mineralize TC promptly and almost completely.
One-dimensional (1D) Ag/AgBr/TiO 2 nanofibres (NFs) have been successfully fabricated by the one-pot electrospinning method. In comparison with bare TiO 2 NFs and Ag/AgBr/PVP (polyvinylpyrrolidone) NFs, the 1D Ag/AgBr/TiO 2 NFs photocatalyst exhibits much higher photocatalytic activity in the degradation of a commonly used dye, methylene blue (MB), under visible light. The photocatalytic removal efficiency of MB over Ag/AgBr/TiO 2 NFs achieves almost 100 % in 20 min. The photocatalytic reaction follows the first-order kinetics and the rate constant ( k ) for the degradation of MB by Ag/AgBr/TiO 2 NFs is 5.2 times and 6.6 times that of Ag/AgBr/PVP NFs and TiO 2 NFs, respectively. The enhanced photocatalytic activity is ascribed to the stronger visible light absorption, more effective separation of photogenerated electron-hole pairs, and faster charge transfer in the long nanofibrous structure. The Ag/AgBr/TiO 2 NFs maintain a highly stable photocatalytic activity due to its good structural stability and the self-stability system of Ag/AgBr. The mechanisms for photocatalysis associated with Ag/AgBr/TiO 2 NFs are proposed. The degradation of MB in the presence of scavengers reveals that h + and • O
− 2
significantly contribute to the degradation of MB.
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