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 (Zn²⁺) release evaluation revealed that ROS play a key role in bacterial inactivation rather than Zn²⁺. 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.
© 2016 Elsevier B.V.

随着纳米科技和材料技术的发展，纳米颗粒的生态毒性越来越受到重视。本项目以ZnO纳米流体为研究对象，研究了ZnO纳米流体的物理、化学和生物特性，并研究了超声外场下,ZnO纳米流体的毒性变化，以及ZnO纳米流体的生态毒性机理。研究表明纳米ZnO流体对革兰氏阴性菌和阳性菌都具有细菌毒性，其细菌的毒性会随着浓度增加、流体中团聚物粒径的降低和超声外场的引入而增加。引入超声外场时，与超声相关的因素如超声的时间、超声频率、超声功率等对ZnO纳米流体的细菌毒性有一定的影响。实验结果显示，低频、高强度的超声能够取得更好的抗菌效果；当超声时间在1min以内时，超声10s取得的抗菌效果最好,1min后，随着时间的增加，抗菌效果也更加明显。在ZnO纳米流体和超声外场作用下，系统中活性氧的存在是ZnO纳米流体产生细菌毒性的原因之一。超声协同ZnO纳米流体在一定程度上使细菌内外膜的通透性发生变化。细胞外膜通透实验的荧光试验结果显示,ZnO纳米流体单独作用时，峰值在1h后取得，在超声的协同作用下，细胞外膜的通透性变化更快，吸光度值在0.5h后达到。然而与单独使用ZnO纳米流体相比，超声的协同并没有增加细胞外膜的通透性。细胞内膜的通透性实验显示在超声的协同作用下，细胞内膜的通透性变化高于单一ZnO纳米流体作用实验组。

Combination of disinfection method gives advantages. In this work, inactivation of E. coli using ZnO nanofluids and ultrasound is evaluated. Growth curves of bacteria were investigated to reveal the inactivation activities of ZnO nanofluids and ultrasound. The effects of combination of ZnO nanofluids and ultrasound, ultrasound time, ultrasound induction point and the induction order of ZnO nanofluids and ultrasound were studied. The results suggested that combination of ZnO nanofluids and ultrasound gives better inactivation effect on E. coli when comparing with single disinfection method. Ultrasound for 10 s helped ZnO nanofluids inhibiting bacteria better than ultrasound for 30 s /60 s. Ultrasound induction point (at 0 hr, 2 hr or 4hr) did not affect on ZnO nanofluids to exhibit the inhibiting property. Induction ultrasound prior to adding ZnO nanofluids showed the better inactivation effect on E. coli. The results also displayed that in this work, ultrasound was mainly worked as a pre-treatment step, instead of a disinfection method. © (2014) Trans Tech Publications, Switzerland.

Due to the rapid elevation of health standards and the limited water resources, decontamination and disinfection have become a challenging aspect of water/wastewater treatment. Traditional disinfection in water/wastewater treatment is associated with limitations, such as the production of toxic disinfection by-products. With the development of nanofluids, there is more and more interest in using nanofluids in environmental sectors, especially in water/wastewater treatment. Nanofluids are not strong oxidants and are not expected to produce harmful disinfection by-products. Nanofluids exhibit good disinfection properties against a wide range of bacteria, including Gram-negative, Gram-positive and spore bacteria. Several patents disclose the typically used types of nanofluids and their possible disinfection/decontamination mechanisms. The use of different nanofluids and their applications in different water/wastewater treatment have also been reviewed in this paper.

Due to the rapid elevation of health standards and the limited water resources, decontamination and disinfection have become a challenging aspect of water/wastewater treatment. Traditional disinfection in water/wastewater treatment is associated with limitations, such as the production of toxic disinfection by-products. With the development of nanofluids, there is more and more interest in using nanofluids in environmental sectors, especially in water/wastewater treatment. Nanofluids are not strong oxidants and are not expected to produce harmful disinfection by-products. Nanofluids exhibit good disinfection properties against a wide range of bacteria, including Gram-negative, Gram-positive and spore bacteria. Several patents disclose the typically used types of nanofluids and their possible disinfection/ decontamination mechanisms. The use of different nanofluids and their applications in different water/wastewater treatment have also been reviewed in this paper. © 2013 Bentham Science Publishers.

This work investigates the disinfection property of ZnO nanofluids, focusing on H2O2 production and the disinfection activities of ZnO suspensions with different particles/aggregates. The possible disinfection mechanisms of ZnO suspensions are analysed. In this work, a medium mill was used to produce ZnO suspensions with different sizes of particles/aggregates. During the milling process, five ZnO suspension samples (A-E) were produced. X-ray Diffraction (XRD) and Dynamic Light Scattering (DLS) analyses revealed that after milling, the size of ZnO particles/aggregates in the suspensions decreased. Disinfection tests, H2O2 detection assays and fluorescent analyses were used to explore the disinfection activities and mechanism of ZnO suspensions. Disinfection tests results showed that all the produced ZnO suspension exhibited disinfection activity against Escherichia coli. ZnO suspensions with smaller particles/aggregates showed better disinfection activities. The presence of H2O2 in ZnO suspension was analysed. The H2O2 detection assay suggested that there is 1μM H2O2 in 0.2g/l ZnO Sample A, while there was no H2O2 present in ZnO Sample E. Though results showed that there was no H2O2 present in ZnO Sample E, Sample E with a size of 93nm showed the best disinfection activities. Fluorescence tests detected that the interaction between E. coli lipid vesicles and ZnO Sample E was much faster and more efficient. This study firstly demonstrated that ZnO suspensions with different particles/aggregates produced different amount of H2O2. Results suggested that H2O2 is responsible for the disinfection activity of larger ZnO particles/aggregates while the interaction between smaller ZnO particles/aggregates and vesicle lipids is responsible for the disinfection activity of smaller ZnO particles/aggregates. © 2013.

This work investigates the disinfection property of ZnO nanofluids, focusing on H2O2 production and the disinfection activities of ZnO suspensions with different particles/aggregates. The possible disinfection mechanisms of ZnO suspensions are analysed. In this work, a medium mill was used to produce ZnO suspensions with different sizes of particles/aggregates. During the milling process, five ZnO suspension samples (A E) were produced. X-ray Diffraction (XRD) and Dynamic Light Scattering (DLS) analyses revealed that after milling, the size of ZnO particles/aggregates in the suspensions decreased. Disinfection tests, H2O2 detection assays and fluorescent analyses were used to explore the disinfection activities and mechanism of ZnO suspensions. Disinfection tests results showed that all the produced ZnO suspension exhibited disinfection activity against Escherichia coli. ZnO suspensions with smaller particles/aggregates showed better disinfection activities. The presence of H2O2 in ZnO suspension was analysed. The H2O2 detection assay suggested that there is 1 mu M H2O2 in 0.2 g/l ZnO Sample A, while there was no H2O2 present in ZnO Sample E. Though results showed that there was no H2O2 present in ZnO Sample E, Sample E with a size of 93 nm showed the best disinfection activities. Fluorescence tests detected that the interaction between E. coli lipid vesicles and ZnO Sample E was much faster and more efficient. This study firstly demonstrated that ZnO suspensions with different particles/aggregates produced different amount of H2O2. Results suggested that H2O2 is responsible for the disinfection activity of larger ZnO particles/aggregates while the interaction between smaller ZnO particles/aggregates and vesicle lipids is responsible for the disinfection activity of smaller ZnO particles/aggregates. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.