The acceleration of globalization has enabled the spread of microbial infections on a large scale in a short period of time, while at the same time, the situation of hospital infections within the healthcare system is becoming increasingly complex. The management of hospital infections is closely related to disinfection and sterilization work. At present, the requirements for disinfection and sterilization are constantly increasing, and personnel in related fields are also pursuing the development of safe, effective, and environmentally friendly antibacterial and disinfectant agents. Micro acidic water electrolysis emerged as a result, and it was first developed in Japan in the late 1990s. Since 1997, scholars have been studying its bactericidal effect and safety. In 2002, slightly acidic water electrolysis was designated as a food fungicide in Japan under the name hypochlorous acid water. Afterwards, it has been applied in other fields and research in the medical field has been carried out successively. The following is a summary of its production mechanism, physicochemical characteristics, bactericidal effect, and application.

1. Introduction to Micro Acidic Water Electrolysis

1.1 Generation of slightly acidic water electrolysis

Micro acidic water electrolysis is a type of acidic water electrolysis. Acidic water electrolysis refers to the use of electrodes to electrolyze diluted saline or hydrochloric acid water, and the resulting product with a pH value of<7 is called acidic water electrolysis. Due to differences in production equipment and electrolyte, different types of acidic water electrolysis can be generated. There are mainly strong acidic water electrolysis and slightly acidic water electrolysis. Strong acidic water electrolysis, referred to as electrolyzed oxidizing water (EOW) in the 2002 edition of China's "Disinfection Technical Specifications", is commonly known as acidic potential water, high redox potential acidic water, strong oxidizing ion water, and functional water. He uses a two chamber or three cell diaphragm electrolysis cell to electrolyze saline solution with a concentration of less than 0.1%, obtaining oxygen, chlorine gas, and H+at the anode. Chlorine gas reacts with water to produce hydrochloric acid and hypochlorous acid; Obtain H and OH at the cathode, making the water alkaline with a pH value greater than 7. Micro acidic water electrolysis is a process in which dilute hydrochloric acid with a concentration of 2% to 6% is electrolyzed in a single chamber, non diaphragm electrolytic cell at a DC voltage of around 2 V. Chlorine gas and H+are generated at the anode, and H+dissolves in water to make it acidic, with a pH value of 5.0-6.5; Chlorine gas reacts with water to produce hydrochloric acid and hypochlorous acid (HCIO), while the cathode only produces hydrogen gas.

1.2 Advantages of slightly acidic water electrolysis

Micro acidic water electrolysis sterilization is efficient, fast, broad-spectrum, safe, environmentally friendly, and cost-effective. Compared with EOW, slightly acidic water electrolysis has the following advantages J1: using dilute hydrochloric acid as raw material, the cost is low; The generating device can continuously operate to generate water electrolysis, and the products generated during the process evaporate with the air and are not easily residual in the environment; In the process of producing slightly acidic water electrolysis, in addition to generating chlorine with bactericidal effects, no oxygen or ozone is produced, and higher-order oxides of chlorine such as HCIO, HCIO, HCIO, etc. are not generated. The concentration of by-products such as dissolved oxygen, ozone, and chlorine oxides is low, making it environmentally friendly; The generated slightly acidic water is electrolyzed into a colorless, transparent, non viscous liquid containing hypochlorous acid Odorless or slightly chlorinated, with a pH value close to 7, it is less harmful to the human body and has almost no corrosiveness to objects. Moreover, after the electrolysis of slightly acidic water, oxidation-reduction reactions occur to generate water, and the raw material does not contain salt. Even if it is dried after use, there will be no harmful effects of salt concentration and crystallization. It can be seen that slightly acidic water electrolysis is ideal for disinfection in medical systems. Its inherent acidity and almost no irritating odor are also beneficial for occupational protection of medical personnel.

1.3 Preservation of slightly acidic water electrolysis

Slightly acidic water electrolysis is prone to oxidation and decomposition upon exposure to light. After being placed in a sealed and shaded environment for 40 days, the effective chlorine concentration is 78% of the initial value, indicating that it needs to be stored in a cold and sealed environment.

1.4 Toxicity of slightly acidic water electrolysis

In Japan, slightly acidic water electrolysis has been used as a food fungicide, indicating that in addition to food testing, a series of toxicity tests such as "single dose toxicity test", "90 day repeated dose toxicity test", "mutagenicity test" have been conducted on designated animals and microorganisms, as well as "skin irritation test", "eye irritation test", etc., with no abnormalities. Its safety is worthy of recognition.

Corrosion of slightly acidic water electrolysis

The pH value of slightly acidic water electrolysis is 5.0-6.5, close to neutral, and has no corrosiveness to stainless steel or other materials.

2. The bactericidal effect of slightly acidic water electrolysis

2.1 Basic and Mechanism of Sterilization

The sterilization basis of acidic water electrolysis is secondary HCIO, which can damage the cell membrane, causing proteases, RNA, and DNA inside the cell to be unable to exert normal biochemical activity, leading to microbial death, and immediately reducing to water upon contact with microorganisms and organic matter. The proportion of HCIO will change with different pH values. When the pH value reaches alkaline, the content of CIO increases, and when the pH value decreases, the amount of chlorine gas will increase. The bactericidal effect of HCIO is 80-100 times that of CIO. HCIO has a high proportion in the pH value of acidic water electrolysis. The pH value of slightly acidic water electrolysis is 5.0-6.5, and about 97% of the active chlorine in this pH range is HCIO. Therefore, slightly acidic water electrolysis with relatively low effective chlorine concentration can also exhibit good bactericidal effect.

2.2 Micro acidic water electrolysis sterilization is highly efficient, broad-spectrum, and fast

It is generally believed that the sensitivity of microorganisms to disinfection factors, from high to low, is as follows: lipophilic viruses, bacterial reproductive forms, hydrophilic viruses, mycobacteria, and bacterial spores. As early as 1987, EOW was developed by Japan as a fungicide with significant efficacy against methicillin-resistant Staphylococcus aureus (MRSA) and began to be applied in the medical field. Early research in our country has demonstrated the excellent bactericidal effect of EOW. The 2002 version of the "Disinfection Technical Specification" and the 2009 hospital infection monitoring specification have allowed its use in intestinal endoscopy disinfection and skin and mucosal disinfection. However, the research on the bactericidal effect of slightly acidic water electrolysis, which emerged later, has not yet been fully conducted. In existing research reports, slightly acidic water electrolysis has shown bactericidal effects on various bacterial colonies and influenza viruses in a short period of time; For bacterial spores, the time required to reach below the inspection criteria at 20 ℃ is 15 minutes for a sodium hypochlorite solution with an effective chlorine concentration of 100 mg/L, while electrolysis of slightly acidic water only takes 5 minutes. The study also showed that the bactericidal effect of slightly acidic water electrolysis increases with temperature, but it is weakened by the influence of organic matter. When using, it is necessary to thoroughly clean the organic matter, which is similar to EOW. There is a specialized study on the bactericidal effect of slightly acidic water electrolysis on the spores of six bacterial genera As a result, it was found that slightly acidic water electrolysis had an inhibitory effect on the reproduction of six types of spores. At 30 ℃, after 10 minutes of electrolysis with a concentration of 102-103 CFU/mL spore solution and slightly acidic water, the germination and reproduction ability decreased to 1/10-1/100. In the experiment of killing Salmonella enterica by slightly acidic water electrolysis, the bactericidal effect was comparable to EOW under the same effective chlorine content; Under three temperature conditions (4 degrees Celsius, 200 degrees Celsius, and 45 degrees Celsius), a 100% killing rate of Salmonella enterica can be achieved after 2 minutes of electrolysis in slightly acidic water with an effective chlorine content of 4 mg/L.

3. Application of slightly acidic water electrolysis

3.1 Application of Micro Acidic Water Electrolysis in Food Processing Industry

Although slightly acidic water electrolysis has low effective chlorine content, it has good bactericidal effect and is environmentally friendly, making it an ideal vegetable fungicide. In practical applications, disinfecting fresh vegetables and grains for consumption, compared with the commonly used sodium hypochlorite, the slightly acidic water electrolysis has a higher sterilization effect, while overcoming the disadvantages of high residual chlorine, difficult post-treatment, and harmful substance trichloromethane generated by sodium hypochlorite used for food disinfection. For common food pathogens such as Staphylococcus aureus and Escherichia coli, they can be completely killed in a short period of time. For Vibrio parahaemolyticus and Vibrio halophilic, which can cause serious food poisoning, micro acidic water electrolysis can kill them within 30 to 8 hours. In vegetable food disinfection, flowing water rinsing or fumigation can be used, and slightly acidic water electrolysis has no effect on the color and quality of the food. Moreover, slightly acidic water electrolysis can maintain effective chlorine content for a long time in a sealed and shaded environment, and can be used as a sealing solution for pipelines in the food processing industry when not in use, as well as for long-term soaking and disinfection of some materials.

3.2 Micro acidic water electrolysis for air disinfection

Slightly acidic water electrolysis has almost no sensory difference from daily flowing water when used. spray can be used to inactivate bacteria or fungi, influenza virus and coronavirus in the air, which can be used to prevent influenza, etc. When using it for air disinfection in primary school and university classrooms with people present, and investigating the subjective air humidity, comfort, and discomfort of the population, the results showed that slightly acidic water electrolysis has a good air disinfection and sterilization effect. In Japan, slightly acidic water electrolysis has begun to be used for air disinfection in nursing facilities, hospitals, restaurants, offices, and other places. In medical environments, commonly used air disinfection methods include ultraviolet irradiation, formaldehyde fumigation, or chemical spraying. These methods not only have a long duration of action, but are also harmful to the human body. In the future, the effectiveness of using slightly acidic water electrolysis for air disinfection in medical environments can be studied to achieve optimal utilization.

3.3 Micro acidic water electrolysis for surface disinfection of objects

In clinical practice, disinfectant solutions (trichloroisocyanuric acid effervescent instant tablets) with concentrations of 500 mg/L or 1000 mg/L are commonly used to wipe treatment surfaces for disinfection. However, disinfectant solutions have a strong chlorine odor, mild corrosiveness, environmental pollution, and a certain degree of irritation to the human throat and eye mucosa. EOW has been widely used as a green, environmentally friendly and efficient disinfectant for surface disinfection of clinical objects. Given the advantages of microacid water electrolysis compared to EOW, further research can be conducted on the effectiveness of microacid water electrolysis in disinfecting the surfaces of objects in the medical field, in order to promote its early application. However, slightly acidic water electrolysis, like EOW, is susceptible to the influence of organic matter and should be taken into account during use.

3.4 Application prospects of slightly acidic water electrolysis in other medical fields

As a type of water electrolysis, EOW has shown good effects in endoscopic disinfection, oral healthcare, hand and skin disinfection for medical personnel, planing, and inflammation treatment. However, the new disinfectant of slightly acidic water electrolysis has not yet received widespread attention. The sterilization of slightly acidic water electrolysis is efficient and fast, and after action, oxidation-reduction reactions occur to generate water, which is non-toxic and environmentally friendly. It can be imagined that the application prospects of slightly acidic water electrolysis in these fields are ideal disinfectants suitable for medical systems.

4. Summary

With the implementation of sustainable development policies and the deepening of green concepts, developing a circular economy and building a resource-saving and environmentally friendly society have become inevitable choices for China's sustainable development. A people-oriented, green and environmentally friendly disinfectant that not only kills microorganisms, but also brings clean air and environment to patients and medical staff. Micro acidic water electrolysis, as an environmentally friendly disinfectant, has broad application prospects. In order to apply it in practice as soon as possible, in-depth experiments can be conducted from multiple aspects in the future to study its bactericidal effect and its application value in the medical field.