Sonophotocatalytic inactivation of E. coli using ZnO nanofluids and its mechanism

Abstract

The present study evaluated inactivation efficiency of a sonophotocatalytic process using ZnO nanofluids including ultrasonic parameters such as power density, frequency and time. The result showed that inactivation efficiency was increased by 20% when ultrasonic irradiation was combined with photocatalytic process in the presence of natural light. Comparison of inactivation efficiency in photocatalytic, ultrasonic and sonocatalytic processes using Escherichia coli as a model bacteria identified that inactivation efficiencies are shown in the following order: ultrasonic irradiation<sonocatalysis<photocatalysis<sonophotocatalysis. Furthermore, inactivation mechanism of sonophotocatalysis was proposed. Studies of reactive oxygen species (ROS) and zinc ions (Zn) release evaluation revealed that ROS play a key role in bacterial inactivation rather than Zn. Permeability of outer membrane (OM) and inner membrane (IM) of E. coli bacterial cells were studied and exhibited that sonophotocatalysis increased the permeability of OM and IM significantly. The enhanced bacterial inactivation effect in sonophotocatalytic process contributed to acoustic cavitation, sonocatalysis of ZnO and sonoporation phenomenon.

Solvothermal Synthesis of M-doped TiO2Nanoparticles for Sonocatalysis of Methylene Blue and Methyl Orange (M = Cd, Ag, Fe, Ce, and Cu)

“…This condition leads to light generation via sonoluminescence and excitation of the catalyst surface . The excited species generate highly reactive radicals . Sonocatalysis and sonoexcitation processes have found uses in different applications, such as sonodynamic therapy, environmental pollution treatment, disinfection, and so on.…”

“…The excited species generate highly reactive radicals . Sonocatalysis and sonoexcitation processes have found uses in different applications, such as sonodynamic therapy, environmental pollution treatment, disinfection, and so on. Inorganic catalysts such as TiO 2, ZnO, MgO, PbSe, CdSe–graphene, and so on, have been used as catalytic sites for sonocatalysis.…”

“…Sonocatalysis and sonoexcitation processes have found uses in different applications, such as sonodynamic therapy, environmental pollution treatment, disinfection, and so on. Inorganic catalysts such as TiO 2, ZnO, MgO, PbSe, CdSe–graphene, and so on, have been used as catalytic sites for sonocatalysis. TiO 2 is the most promising sonocatalyst because of its characteristic of biocompatibility, nontoxicity, and long‐term chemical and catalytic stability …”

Water disinfection using acoustic cavitation: A mini review

“…Important configurations of sonochemical reactors are given below-1.Ultrasonic horn and bath 2.Dual frequency flow cell 3.Triple frequency fuel cell 4.Ultrasonic bath with longitudinal vibrations Ultrasound can be generated by various gas and liquid driven transducers, electromechanical transducers like magnetostrictive and piezoelectric. Ultrasonic bath, probe and the ultrasonic flow cell are commonly used sonication equipment (L. Zhang et al, 2017). Gogate and Kabaddi (2009) describes details of hydrodynamic cavitation, according to them hydrodynamic cavitation generated by the high RPM of any object in liquid medium.…”

Kinetics of inactivation and photoreactivation of Escherichia coli using ultrasound-enhanced UV-C light-emitting diodes disinfection

“…It can be concluded that the US pretreatment enhanced the disinfection efficiency, and resulting in a low E.coli concentration in the effluent, therefore, the photoreactivation reduced. Secondly, it is hypothesized that the radicals OH generated during sonication create some sub-lethal damage effect on the cell walls and enzymes, changing the permeability of cell walls or blocking the enzymes' synthesis [29,30]. However, the exactly effect of US in the photoreactivation process is required for further verification.…”