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Inactivation of pathogens by ozone synergistic technology

At present, synergistic disinfection methods based on ozone oxidation technology mainly focus on the following four aspects: ultraviolet synergistic ozone (UV+O3), hydrogen peroxide synergistic ozone (H2O2+O3), ultrasonic synergy ozone and heterogeneous catalysis synergistic ozone technology. Pure ozone disinfection will produce harmful disinfection by-product bromate, which will affect the killing effect of pathogens. The researchers controlled the reaction pH and ozone concentration to suppress the production of by-products. In addition, the sterilization efficiency of pure ozone method is low and relatively expensive, and the economic benefit ratio is low. Therefore, a reasonable ozone-assisted collaborative disinfection system has been paid more and more attention. Ozone Sterilizer

The inactivation effect of ozone synergistic disinfection technology on pathogens is significantly better than that of pure ozone method. The mechanism of action of UV synergistic ozone technology is shown in formulas (1) to (3).

O3+H2O+hv → H2O2+O2 (1)
2O3+H2O2 → 2•OH+3O2 (2)
H2O2+hv → 2•OH (3)

Under the action of ultraviolet light, ozone molecules will generate hydrogen peroxide molecules, which will not only react with ozone molecules, but also directly decompose under ultraviolet light to generate more oxidative hydroxyl radicals. RL Wolfe et al. studied the inactivation of Giardia muris by hydrogen peroxide combined with ozone technology, and also evaluated the inactivation effect of microorganisms such as Escherichia coli and MS2 phage, and found that they have excellent inactivation effects. Especially the inactivation effect on Giardia muris reached 8.0-log10, and the CT value was 5.4 mg·min/L. The synergy between hydrogen peroxide and ozone is mainly because hydrogen peroxide can directly react with ozone molecules to generate hydroxyl radicals. The mechanism of action is shown in formula (4).

H2O2+2O3 → 2•OH+3O2 (4)
The mechanism of action of ultrasonic technology in synergy with ozone technology is shown in equations (5) to (7). In the formula, “(((” is the ultrasonic identifier, and “O(3P)” represents the reactive oxygen species generated after the ozone molecule is decomposed by ultrasonic excitation.
H2O + ((( → • OH + • H (5)
O3 + (((→ O2 + O(3P) (6)
O(3P)+H2O → 2•OH (7)

It can be seen that ultrasonic technology can not only directly generate hydroxyl radicals from water molecules, but also help ozone molecules to decompose into hydroxyl radicals, thereby significantly improving the inactivation effect. GR Burleson et al. found that ultrasonic technology alone has no obvious inactivation effect on Escherichia coli (Escherichia coli), encephalomyelitis virus (GDVII), and myocarditis virus (Encephalomyocarditis), but ultrasonic combined ozone technology has better inactivation efficiency than pure ozone technology. Significantly improved, can reach 100% virus inactivation rate, indicating the advantages of ozone synergistic disinfection technology compared to pure ultrasonic technology.

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In recent years, extensive research on heterogeneous catalysis technology has provided the basis for heterogeneous catalysis synergistic ozone. As one of the efficient, green and low-cost process technologies, heterogeneous catalysis ozone has been widely used in the field of sterilization and disinfection. Compared with the above three types of synergistic technologies, the heterogeneous catalysis synergistic ozone technology has significant advantages in inactivating bacteria and viruses. For example, under the irradiation of sunlight or ultraviolet light, the widely used photocatalytic material P25 type TiO2 cooperates with ozone technology to treat Escherichia coli, Salmonella, Shigellar and Vibrio4 All kinds of bacteria can achieve 100% inactivation rate. In addition, compared with pure ozone technology, the required inactivation time is reduced by 50% to 70%, and the regeneration of bacteria can be inhibited. LT Kist et al. 139] also used P25 type TiO2 to inactivate Escherichia coli in actual wastewater by photocatalytic synergy with ozone under ultraviolet light, and within 60 minutes of the test setting time, it reached 100%. Inactivation effect, the designed wastewater treatment circulation system in the experiment provides the possibility to solve the practical problems in the disinfection process.

N. Moreira et al. studied the effect of P25 TiO2 on light-emitting diodes (LEDs) by high-throughput sequencing, using a variety of resistance genes (ARGs) in Escherichia coli as indicators, including 16S rRNA, intI1, blaTEM, etc. The inactivation effect of photocatalytic synergistic ozone technology on Escherichia coli under UV lamp. Under the set experimental conditions, the inactivation efficiency is the same for Escherichia coli or resistance genes (ARGs) detection. more than 90%. Kuopin Yu et al. 138] used TiO2 as a substrate and loaded nano-metal silver, copper and nickel on it. This series of photocatalytic materials and ozone technology can play a role in synergistic antibacterial disinfection. The inactivation kinetics of Aspergillus niger (A. niger) showed that under the dosage of 2 mg/cm2 modified catalyst, the inactivation kinetic constant of synergistic ozone was k=0.475~0.966 h−1, which was the same as that without ozone at the same concentration. The inactivation efficiency is 4-475 times higher, and the difference in the loading of nano-metals will lead to the difference in inactivation effect. In addition, the research of Kuopin Yu et al. also revealed the mechanism of synergistic inactivation. The inactivation effect is directly related to the loading of nano-metals. The added material can promote the decomposition of ozone and generate hydroxyl radicals with higher activity. High inactivation effect, as shown in formula (8) ~ formula (10).

Material −O3• → Material −O•+O2 (8)
Material −O•+H2O→2•OH (9)

O3/ROS+ pathogens (bacteria, protozoa, viruses, etc.) → inactivation (10) Heterogeneous catalysis synergistic antivirus technology not only has the advantages of high efficiency and greenness, but also compared with pure UV, ozone and ultrasonic sterilization and disinfection technologies. It can well inhibit the regeneration of bacteria or viruses, mainly because the heterogeneous catalytic material catalyzes ozone to generate more efficient hydroxyl radicals (1 formula (8) ~ formula (10)], thus greatly improving the killing of ozone technology. efficiency, and the continuous generation of free radicals can also achieve the effect of inhibiting regeneration. AC Mecha et al. 141] compared TiO2 and TiO2 loaded with silver, copper, and iron against four pathogens, including Escherichia coli, Salmonella, and Shigellar, under UV or sunlight. , the inactivation effect of Vibrio and the regeneration after inactivation. Compared with pure light or ozone inactivation, photocatalytic synergistic ozone inactivation can significantly reduce the time required for the inactivation rate to reach 100% (reduced by 50%~75%), indicating that the synergistic inactivation technology has a very rapid response. dynamics. In addition, the synergy index of TiO2 and modified TiO2 with ozone can reach more than 1.86, indicating a very high synergistic effect. In addition, another obvious advantage of photocatalytic synergistic ozone oxidation comes from the regeneration inhibition effect on the four pathogens. After inactivation by the synergistic technology, the regeneration rate of the four pathogens in the regeneration experiment is 100% under the action of ultraviolet light or visible light. zero, indicating the continued inactivation advantage of the synergistic technology.

The simple ozone method has good applicability in various fields because of its simple operation, but its low efficiency and the formation of toxic by-products restrict its development. Ultraviolet synergistic ozone (UV+O3), hydrogen peroxide synergistic ozone (H2O2+O3) and ultrasonic synergistic ozone greatly enhance the active oxygen species generated by ozone decomposition, thereby improving the killing efficiency and are more widely used. In addition, heterogeneous catalytic synergistic ozone technology has more efficient killing efficiency and low potential toxicity, and has the advantages of reusability and low cost. As an emerging technology, heterogeneous catalytic ozone technology still needs to be promoted in the future. Heterogeneous catalytic synergistic sterilization technology will be gradually applied to the new coronavirus (SARS-CoV-2) in the future due to its high yield of reactive oxygen species, pathogen inactivation efficiency, reusability, and low cost. Kill and spread blocking.