Boosting visible light photocatalytic and antibacterial performance by decoration of silver on magnetic spindle-like bismuth ferrite

Abstract Visible light-activated Ag-doped spindle-like BiFeO3 (Ag-BFO) magnetic nanocomposite using different Ag loadings was synthesized via hydrothermal synthesis methods. The structural, morphological, optical and magnetic properties of as-prepared nanocomposite was analyzed by various characterization techniques. Field emission scanning electron microscopy images revealed the distribution of metallic Ag on the surface of spindle-like BFO with the widths ranging from 30 to 60 nm and the lengths from 200 to 250 nm. The X-ray photoelectron spectroscopy spectra showed that the electronic states of Bi3+, Fe3+ and Ag0 existed in the Ag-BFO nanocomposite. UV–Vis diffuse reflectance spectra showed a red-shift on the light absorption edges after the loading of metallic Ag. Fourier transform infrared spectroscopy studies confirmed the presence of metallic Ag and Fe−O bond of FeO6 octahedral perovskite structure. The photocatalytic results presented that the Ag-BFO nanocomposite exhibited boosted visible light photoactivity on the degradation of malachite green (MG) dye. Especially, the 3 wt% Ag-BFO nanocomposite displayed excellent photoactivity than that of the pure BFO. The boosted photoactivity of Ag-BFO nanocomposite can be credited to the high electron-hole pairs separation efficiency and hydroxyl (•OH) radicals generation capability as witnessed by photoluminescence and terephthalic-photoluminescence (TA-PL) measurements. The Ag-BFO mineralization of MG dye under different light sources suggested that around 90.5% COD removal was achieved under sunlight irradiation, while 20.9% and 33.9% of COD were removed under visible and UV light irradiation, respectively. Other organic substances such as methylene blue, sunset yellow, phenol and 2,4-dichlorophenoxyacetic acid were also successfully degraded under the identical condition. Moreover, the Ag-BFO nanocomposite retained its photoactivity and morphological stability even after five recycling runs. The separation of Ag-BFO nanocomposite from the aqueous suspension was also relatively easy due to its strong ferromagnetism property. The radical scavengers study also showed that hole (h+), hydrogen peroxide (H2O2) and •OH radicals were the core active species for the Ag-BFO nanocomposite catalytic system. Furthermore, the Ag-BFO nanocomposite showed much improved antibacterial activities towards the Escherichia coli and Micrococcus luteus in comparison with the pure BFO. These findings presented that the Ag-BFO magnetic nanocomposite can be utilized as photocatalytic and antimicrobial agents for the prospective practical applications in the wastewater treatment.