A novel Z-scheme sonocatalyst system, Er3+:Y3Al5O12@Ni(Fe0.05Ga0.95)2O4-Au-BiVO4, and application in sonocatalytic degradation of sulfanilamide

A novel Z-scheme coated composite, Er 3+ :Y 3 Al 5 O 12 @Ni(Fe 0.05 Ga 0.95 ) 2 O 4 -Au-BiVO 4 , was designed for sonocatalytic degradation of sulfanilamide and fabricated by sol-hydrothermal and calcination methods. The prepared sample was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), UV–vis diffuse reflectance spectra (DRS), fourier transform infrared (FT-IR) spectra, Raman spectra and photoluminescence (PL) spectra. In Er 3+ :Y 3 Al 5 O 12 @Ni(Fe 0.05 Ga 0.95 ) 2 O 4 -Au-BiVO 4 , Ni(Fe 0.05 Ga 0.95 ) 2 O 4 and BiVO 4 form a Z-scheme sonocatalytic system, Er 3+ :Y 3 Al 5 O 12 as an up-conversion luminescence agent (from visible-light to ultraviolet-light) provides the ultraviolet-light for satisfying the energy demand of wide band-gap Ni(Fe 0.05 Ga 0.95 ) 2 O 4 and Au nanoparticles as co-catalyst forms more active sites to enrich electrons. Also, Au nanoparticles as conductive channels promotes the electrons (e − ) from conduction band of BiVO 4 to transfer to valence band of Ni(Fe 0.05 Ga 0.95 ) 2 O 4 . Due to the characteristics of valence state diversity, the Fe 3+ and V 5+ constitute a redox reaction recombination system, which can also push electrons (e − ) on conduction band of BiVO 4 to quickly transfer to valence band of Ni(Fe 0.05 Ga 0.95 ) 2 O 4 . The sonocatalytic activity of Er 3+ :Y 3 Al 5 O 12 @Ni(Fe 0.05 Ga 0.95 ) 2 O 4 -Au-BiVO 4 nanocomposite was detected through degradation of sulfanilamide under ultrasonic irradiation. A high sonocatalytic degradation ratio (95.64%) of sulfanilamide can be obtained when the conditions of 10.00 mg/L sulfanilamide, 1.00 g/L Er 3+ :Y 3 Al 5 O 12 @Ni(Fe 0.05 Ga 0.95 ) 2 O 4 -Au-BiVO 4 , 300 min ultrasonic irradiation and 100 mL total volume were adopted. Some factors such as ultrasonic irradiation time and cycle number on the sonocatalytic degradation efficiency are also investigated by using TOC and UV–vis spectroscopy. Subsequently, the effects of hydroxyl radicals ( OH) and hole scavengers were investigated to elaborate the mechanism. The researches show that the prepared Z-scheme Er 3+ :Y 3 Al 5 O 12 @Ni(Fe 0.05 Ga 0.95 ) 2 O 4 -Au-BiVO 4 coated composite displayed an excellent sonocatalytic activity in degradation of sulfanilamide under ultrasonic irradiation.