Since China introduced foreign chlorine dioxide products and began to study its production technology in 1980s, after more than ten years, not only domestic chlorine dioxide products have been produced, but also the production technology has been greatly improved, and the problem of chlorine dioxide as an oxidation disinfectant has also been recognized and applied. With the wide application of products, the development of product dosage forms has been promoted. At present, there are chlorine dioxide generators, stable chlorine dioxide, tablets and other solid chlorine dioxide products. The situation of chlorine dioxide dosage forms used for disinfection is summarized as follows.
1. chlorine dioxide generator
Properties and preparation of 1. 1 chlorine dioxide
Chlorine dioxide is an oxide of chlorine, which has a pungent smell similar to chlorine. The molecular formula is ClO2, the molecular weight is 67.457, the melting point is -59℃, and the boiling point is 1 1℃. It exists as a gas at room temperature and is a yellow-green gas. With the increase of concentration, the color becomes orange-red, and the gas chlorine dioxide is extremely unstable. Chlorine dioxide is easily soluble in water, and its solubility is 107.98mg/L/L at 20℃. It can be made into unstable liquid, and its liquid and gas are sensitive to temperature, pressure and light. When the air content is higher than 10%, the spark can be detonated [1]. Chlorine dioxide is an unstable compound, and it is also an unstable compound in air.
The methods of preparing chlorine dioxide by chlorine dioxide generator mainly include electrolytic method and chemical method. The widely used electrolysis method is diaphragm electrolysis, which uses salt as raw material to generate mixed solution containing chlorine dioxide, sodium hypochlorite, hydrogen peroxide and ozone under the action of electric field. The concentration of chlorine dioxide is generally only about 10-30%, and most of it is chlorine. Chemical methods mainly include two methods to generate chlorine dioxide from sodium chlorate and sodium chlorite. In the process of producing chlorine dioxide by sodium chlorate method, if chloride ion is used as reducing agent, the produced chlorine dioxide has the disadvantage of low purity, while the proportion of chlorine dioxide produced by sodium chlorite method is higher, generally above 90%.
1.2 Equipment and sterilization performance
The generators imported from abroad mainly include Tetralarent Company, Rio Lindo Company, Prominent Company of Germany, etc. Li et al. [3] reported the synergistic sterilization effect of chlorine dioxide cooperative sterilizer of Tetralarent Company. The generator uses electrolytic salt solution to generate chlorine dioxide, chlorine gas, ozone and hydrogen peroxide at the same time, which is dissolved in water and has synergistic sterilization effect, and its sterilization effect is better than any of the above disinfectants. The experimental results also show that the electrolytic voltage of the electrolyzer. Huan Pengcheng et al. [4] observed the disinfection effect of Vulcan Rio Linda T 140 chlorine dioxide generator in America. The concentration of chlorine dioxide generated by the generator can be adjusted to 2000-300mg /L, killing Escherichia coli and Staphylococcus aureus1mg/L for 3 minutes, and killing Bacillus subtilis var. The spore of Aspergillus Niger is 65438 0.25mg/L 5. Destroying HBsAg125mg/L for 2min, the minimum concentration of energy experiment is 400 mg/L, and 25% and 50% calf serum protective bacteria solution can affect the sterilization effect. At low concentration (10mg/L), the generator has slight corrosion to copper, carbon steel and aluminum, and basically has no corrosion to stainless steel.
The domestic chlorine dioxide generator has developed rapidly and the process is gradually mature [5]. At present, chlorine dioxide produced by electrolytic salt and positive and negative pressure chlorine dioxide generators produced by sodium chlorate and sodium chlorite methods have been used, and some products have obtained national patents. According to the working principle and operation characteristics of preparing chlorine dioxide mixed disinfectant by electrolysis, Ren [6] adopted single chip microcomputer technology and residual chlorine detector to realize the automatic control of the whole process of adding salt, discharging alkali and adjusting operation of chlorine dioxide disinfection equipment, which greatly improved the disinfection efficiency and the safe transportation of the equipment. Chlorine dioxide produced by chemical method has high content. The generator for producing chlorine dioxide by chemical method developed by Shi Laishun et al. [7] has the available chlorine content of 3246.6438 0 mg/L as determined by iodometry, and the solution contains chlorine dioxide and chlorine gas as detected by ultraviolet spectrophotometer and infrared spectrophotometer, in which chlorine dioxide accounts for 60%-70%. The germicidal efficacy of the aqueous solution showed that it contained 4.5-5.0 mg/L of active ingredients and acted on Staphylococcus aureus, Escherichia coli and Candida albicans in water for 65,438 0-2 minutes, and Bacillus subtilis was a variety. Niger contains 90 mg/L of active ingredients for 5 minutes. The antigenicity of HBsAg can be destroyed by the active ingredient containing 400 mg/L for 5 minutes. The performance of chlorine dioxide disinfectant in chlorine dioxide generator is unstable [8], and the degradation rate is 14.05% after storage for 3 days. However, if analytically pure sodium hydroxide is added to the disinfectant stock solution, the PH value is adjusted to 1 1.80, sealed and protected from light, and stored at room temperature (18 C-25.
Application of 1.3 in disinfection
At present, chlorine dioxide generator is mainly used for drinking water disinfection and sewage treatment. Traditional chlorine-containing disinfectants used for drinking water disinfection will produce a large number of halogenated hydrocarbons when treating raw water, including trihalomethanes such as chloroform and organic halides such as chlorophenol and dichloroacetonitrile [9] [10] [11], and chloroform has been confirmed as a carcinogen by the National Cancer Institute of the United States [1]. The oxidative degradation of organic matter in water will not produce chlorinated products like chlorine-containing disinfectants. In the study of using chlorine dioxide instead of chlorine gas as water treatment, it is shown that the content of trihalomethane in water treated with chlorine gas is 100% higher than that treated with chlorine dioxide, so the use of chlorine dioxide can greatly reduce the production of chloroform and also oxidize iron, manganese, magnesium ions and sulfides in water. It does not react with phenols in water and does not produce unpleasant odor [14], so chlorine dioxide is a promising water disinfectant that can replace chlorine. At present, more and more developed countries in Europe have made chlorine dioxide more effective than chlorine. The Yangtze River water was treated with 0.5 mg/L chlorine dioxide for 30 minutes. Put Minhang water into 1.0- 1.5 mg/L, and the disinfection standard can be reached in 30 minutes.
Chlorine dioxide is used in sewage treatment, besides disinfection, it can also be used to destroy compounds that produce odor and odor, control the growth of algae in water, remove turbidity, improve flocculation and decoloration. And the dosage can meet the national sewage discharge standard calculation.
2. Stable chlorine dioxide solution
2. 1 Properties and preparation of stable chlorine dioxide
Stable chlorine dioxide solution: chlorine dioxide gas is dissolved in stabilizers such as sodium carbonate, sodium percarbonate, sodium borate and sodium perborate. Usually, it is a colorless, odorless and transparent aqueous solution with a concentration within 65,438+00%. It is not flammable and volatile. Stable chlorine dioxide has no bactericidal ability. Chlorine dioxide in the solution can only be released again through activation (acidification) reaction, so it can have strong bactericidal ability. The PH value of activated 2% aqueous solution is acidic. The specific gravity is1.03-1.04 (20 C 0.04 (20 C)), and the aqueous solution is light yellow. After activation, the solution is unstable, and the content can be reduced by 80% after storage for one day [16], which is suitable for current use.
The domestic production methods of stable chlorine dioxide are mostly chemical methods. There are many chemical production processes with sodium chlorate as raw material, and most reducing agents are hydrochloric acid, sulfur dioxide and methanol. This method has low cost, and there are also production methods using sodium chlorite as raw material.
In order to improve the activation speed and rate of stable chlorine dioxide, a lot of research has been done on activators in China. Activators can be divided into quick-release activators that can be completely released in a short time, such as strong acids such as hydrochloric acid and phosphoric acid, and slow-release activators, mainly weak acids such as citric acid. Experiments show that citric acid can only activate 60% of chlorine dioxide. Due to the incomplete release of active chlorine dioxide, there are still more toxic chlorites in the solution, and hydrochloric acid can make chlorine dioxide. In order to improve the inconvenience of using liquid activator, solid activator has also been developed in China. The experimental results show that the activation effect of oxalic acid plus aluminum trichloride is the same as that of hydrochloric acid [18], and the volume ratio of stable solution to activator is usually 10: 1.
2.2 bactericidal performance
Stable chlorine dioxide is a broad-spectrum and efficient disinfectant, which can kill bacterial propagules, spores, fungi and viruses [19]. Wang Fuyu et al. [20] observed the disinfection effect of stable chlorine dioxide solution, and the results showed that when the concentration of 2.0 mg/L 1 min was used, the contaminated Escherichia coli could be reduced by 5-6 logarithm values (the killing rate was 99.999%-99.9999%), and the Escherichia coli phage f 2 could be killed. Juet al. [2 1] reported that treatment with 50 mg/L stable chlorine dioxide 1 min could completely kill Escherichia coli and Staphylococcus aureus, and the killing rate of Bacillus subtilis was var. 500 mg/L Aspergillus Niger spores were exposed to 100% for 30 minutes, which completely destroyed the antigenicity of HBsAg. Chlorine dioxide has a good killing effect on mycobacterium tuberculosis. It has been reported that at 20℃, chlorine dioxide can kill all 10-20 minutes [22]. The concentration of 1 100 mg/L can kill Mycobacterium tuberculosis on endoscope for 5 minutes [23]. Wei Lanfen et al. [24] carried out germicidal efficacy and metal corrosiveness tests on chlorine dioxide solution with 2.55% content and PH value of 6.0. Results The concentration of 160 mg/L was applied to E.coli 10 minute, and the concentration of 200 mg/L was applied to Staphylococcus aureus for 2 minutes. The killing rate reached 100%, and stainless steel was made. Immersion of 400 mg/L chlorine dioxide solution in aluminum, copper and carbon steel for 72 hours has severe corrosion and moderate corrosion to stainless steel. The author thinks that the reason why the solution needs high concentration and action time to kill microorganisms may be related to the high PH value of the solution. In the laboratory, the bactericidal effect of 400 mg/L chlorine dioxide activated by citric acid on enterohemorrhagic Escherichia coli O 157: H7 strain and its influencing factors were observed. At 25℃, the bactericidal D value of the strain was 1.53 minutes, and the bactericidal rate reached 99.99% after 7 minutes, and its concentration coefficient was 1.36, that is, at 25℃, the action time needed to be prolonged by 2.57 times, and the humidity coefficient (Q 10) was 0. Disinfectant has a good bactericidal effect under acidic conditions (PH3-5), and the bactericidal effect is obviously reduced when the PH value is >: 7 [25]. The acute toxicity and irritation test of stable chlorine dioxide [26] showed that oral LD50 >: 10000mg/kg was actually a non-toxic substance, and the 48-hour irritation score of the solution containing chlorine dioxide 9.7- 1 1.4 mg/L on rabbit skin and eye mucosa was zero and there was no irritation. The stable chlorine dioxide products produced in Shanghai can basically reach LD50 >: 5000mg/kg, and the skin irritation index >; 0.4, the result of micronucleus test was negative.
2.3 Application
1985 the United States agreed to use chlorine dioxide as a disinfectant for food processing equipment, and 1987 approved it as an environmental surface disinfectant for food processing plants. China has also approved the disinfection of pipelines, equipment containers and tableware in the food industry, with a concentration of 250 mg/L.
In the field of medical care, the United States has approved the use of fungicides in hospitals, laboratories and medical environments, and China has also approved the use of fungicides in the disinfection of environmental surfaces in the above departments, and can also be used for the disinfection of corrosion-resistant medical devices, such as thermometers, vaginal dilators, oxygen humidification bottles, test tubes and glass slides. , used for disinfection of ventilators, hemodialysis machines, anesthesia machines, baby incubators, etc., but generally not suitable for long-term immersion disinfection of medical devices, the common concentration is 500-650.
In addition, China formulated GB 2760-1996 "Hygienic Standard for the Use of Food Additives" in1996, and listed stable chlorine dioxide as a "preservative" in food additives, which was used in fruit and vegetable preservation and fish processing industries, with the maximum dosage of 0.2-1.0 mg/L.
3. Solid chlorine dioxide disinfectant
3. 1 dosage forms and preparations
Solid chlorine dioxide products include powder, tablet and binary packaging products.
Solid chlorine dioxide mostly uses sodium chlorite as the main raw material. At present, chlorine dioxide binary packaging products are prepared from sodium chlorite and acidic activator, and chlorine dioxide adsorption preparation is formed by sodium chlorite solution adsorbing on bentonite sodium salt or chlorine dioxide gas adsorbing on carriers such as calcium silicate, silicon dioxide, talcum powder and sodium percarbonate dry powder. In addition, there is a production process of non-absorbent chlorine dioxide solid disinfectant. Jiang Xingjin [27] activated sodium chlorite with solid mixed acid agent to generate chlorine dioxide. As a result, only 29%-56% of chlorine dioxide in sodium chlorite is activated by solid organic acids such as citric acid and oxalic acid. However, if organic acid and inorganic acid salt are mixed in the ratio of 1: 1-9, the activation rate can reach above 90%. The author also observed the appropriate amount of water added and the best activation time. Results The amount of water added was 10 times that of solid organic acid, and the best effect was standing for 10 min.
3.2 bactericidal performance
The activation rate and germicidal efficacy of chlorine dioxide show that activation is related to PH value. At PH & lt0.5, the activated chlorine dioxide can be released quickly; at pH >:0.5, the chlorine dioxide release speed is slow, the activation is incomplete, and the sterilization ability is weak. The disinfection effect of chlorine dioxide in binary packaging reported by Jia Songshu [28] is that the average chlorine dioxide content of the product is 6.74%, and the average chlorine dioxide content after storage at 54 C14 days is 6.736%, with no obvious change. The killing rate of 7.5 mg/L solution to Escherichia coli and Staphylococcus aureus was 150 mg/L, and the killing rate to Bacillus subtilis was var. The spore of Niger is 100% continuous 10 minute. The antigenicity of purified HBsAg diluted to 20 mg/ml can be destroyed by using 200 mg/L solution for 5 minutes. 200 mg/L solution has slight corrosion to stainless steel and moderate corrosion to copper and aluminum. In addition, the damage of rubber products was observed. The results showed that the breaking strength and elongation at break of latex tube were decreased after being soaked in 200 mg/L solution for many times, but the difference was not significant (P
3.3 Application of disinfection
Solid chlorine dioxide is convenient for storage and transportation, but it must be activated before use, and attention should be paid to the current use, and the scope of use is the same as that of liquid stable chlorine dioxide.
4. Conclusion
To sum up, the research and application of chlorine dioxide dosage forms are constantly expanding and deepening. The existing chlorine dioxide generator, stable chlorine dioxide solution and solid chlorine dioxide powder or tablet all have strong bactericidal effect. Because no carcinogen is produced in the disinfection process, it is non-toxic and harmless to human body and has broad application prospects. However, because chlorine dioxide is a new disinfectant, especially in the research and application of new dosage forms, there are still many problems worthy of further study, such as improving the stability and activation rate of solid chlorine dioxide, reducing the corrosiveness to metals, and establishing a rapid content detection method for field use. It is expected that through efforts, the application research of chlorine dioxide will achieve better results.