Supported heterogeneous nanocomposites (SiO2/Fe3O4/Ag2WO4) for visible-light-driven photocatalytic disinfection against E. coli

In this work, reusable magnetic heterogeneous nanocomposites (SiO2/Fe3O4/Ag2WO4 ) have been successfully synthesized via a facile co-precipitation method and applied as visible-light responsive photocatalysts for photocatalytic disinfection of Escherichia coli (E. coli). The synthesized materials were characterized using several techniques such as Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), transmission electron microscope (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), UV-visible diffuse reflector spectroscopy (UV-DRS), and vibrating sample-magnetometer (VSM). The SiO2/Fe3O4/Ag2WO4 showed improved antibacterial activity compared with SiO2/Fe3O4 and Ag2WO4 by reducing the cell density from 9.5-log to 1.5-log after 120 min of visible light irradiation. The kinetics studies confirmed that the SiO2/Fe3O4/Ag2WO4 photocatalyst has a maximum disinfection rate (k(max)) of 0.01319 min(-1) which is approximately 1.53 times greater than that of pure Ag2WO4 nanoparticles. This result is due to the synergistic effects between Ag2WO4 and the supporting structure (SiO2). Experimental parameters that affect the photocatalytic E. coli inhibition were investigated, including pH value, catalyst loading, and initial E. coli concentration. The scavenger experiments demonstrated the important roles each of (OH)-O-center dot and H2O2 in the photocatalytic disinfection activity against E. coli. The proposed mechanism of E. coli disinfection was well explained based on scavenger studies and DRS analysis. The stability and reusability studies confirmed the good stability and easy magnetic separation of SiO2/Fe3O4/Ag2WO4 during the five successive cycles.

Automated summary

In this study, reusable magnetic heterogeneous nanocomposites (SiO2/Fe3O4/Ag2WO4) were synthesized and applied as photocatalysts for visible-light responsive photocatalytic disinfection of E. coli. The synthesized materials were characterized using various techniques, and the SiO2/Fe3O4/Ag2WO4 photocatalyst showed improved antibacterial activity compared to other materials. Kinetics studies confirmed the higher disinfection rate of SiO2/Fe3O4/Ag2WO4, and the important roles of (OH)-O-center dot and H2O2 in the photocatalytic disinfection activity were demonstrated. Stability and reusability studies confirmed the good stability and easy magnetic separation of SiO2/Fe3O4/Ag2WO4.