Photocatalytic inactivation of Escherichia coli by natural sphalerite suspension: Effect of spectrum, wavelength and intensity of visible light

The photocatalytic disinfection of Escherichia coli K-12 is investigated by the natural sphalerite (NS) under different spectra, wavelengths and intensities of visible light (VL) emitted by light-emitting-diode lamp (LED). The spectrum effect of VL on disinfection efficiency is studied by using white LED, fluorescent tube (FT) and xenon lamp (XE), which indicates that the “discreted peak spectrum” of FT is more effective to inactivate bacteria than “continuous spectrum” of LED and XE. Besides, the photocatalytic disinfection of bacteria is compared under different single spectrum (blue, green, yellow and red color) LEDs. The results show that the most effective wavelength ranges of VL for photocatalytic disinfection with the NS are 440–490 and 570–620 nm. Furthermore, a positive relationship is obtained between the disinfection efficiency and the VL intensity. The experiment shows that NS can completely inactivate 107 cfu mL−1E. coli K-12 within 8 h irradiation by white LED with the intensity of 200 mW cm−2 at pH 8. Moreover, the destruction process of the cell wall and the cell membrane are directly observed by TEM. Finally, no bacterial colony can be detected within a 96 h regrowth test of inactivated bacteria, which reveals that the VL-photocatalytic disinfection leads to an irreversible damage to the bacterial cells.

The spectrum and wavelength of VL source are the two important parameters for efficient photocatalytic disinfection of E. coli K-12 by NS-VL system.Figure optionsDownload as PowerPoint slideHighlights
► The NS effectively photocatalytic disinfect Escherichia coli K-12 by VL.
► LED is used as a new developing VL source.
► The “discreted peak spectrum” is more effective than the “continuous spectrum”.
► Photocatalytic disinfection is also related to wavelength and intensity of VL.