ozone

scanning: author: from: time:2022-07-28 classify:选购指南
Ozone, the chemical molecular formula for O3, also known as three atomic oxygen, superoxygen, because of its fishy odor, it can be reduced to oxygen at room temperature. Higher specific gravity than oxygen, easily soluble in water, easy to decompose. Because ozone is composed of oxygen molecules carrying an oxygen atom, it is only a temporary state, carrying oxygen atoms in addition to oxidation, the rest of the combination of oxygen into a stable state, so ozone has no secondary pollution.

ozone

 
   
This entry on ozone is reviewed by the "KOPP China" Science Encyclopedia entry compilation  and application work project.
Chemical formula O3, formula quantity 47.998, an allotrope of oxygen.  A pale blue gas with a fishy smell.  Ozone has strong oxidation, is a stronger oxidant than oxygen, can take place at a lower temperature oxidation reaction, such as silver oxidation to silver peroxide, lead sulfide oxidation to lead sulfate, with potassium iodide reaction to iodine.  Turpentine, gas, etc. can spontaneously ignite in ozone.  Ozone is a strong bleaching agent in the presence of water.  Unsaturated organic compounds also tend to form ozonates at low temperatures.  Used as a strong oxidant, bleaching agent, fur deodorizer, air purifier, disinfection fungicide, drinking water disinfection deodorization.  Ozone can be used to replace many catalytic oxidation or high temperature oxidation in chemical production to simplify the production process and improve productivity.  Liquid ozone can also be used as an oxidant for rocket fuel.  Exists in the atmosphere, close to the earth's surface concentration of 0.001 ~ 0.03 PPM, is generated by the oxygen in the atmosphere to absorb the sun's wavelength is less than 185nm ultraviolet rays, the ozone layer can absorb the harmful short-wave rays in the sun (below 30nm), prevent such short-wave rays from the ground, so that human beings from the damage of ultraviolet rays.  [1]     
Chinese name
Ozone
English name
Ozone
called
superoxide
chemical formula
O₃
molecular weight
47.9982
CAS accession number
10028-15-6
EINECS accession number
233-069-2
melting point
-192℃
boiling point
-111℃
water soluble
1 volume of water dissolved 0.494 volume Ozone
dense
2.14g/L(0°C,0.1MPa)
appearance
Blue gas at room temperature
should be used
in medicine, agriculture, catering industry, sterilization, in addition to formaldehyde and other
safety description
workplace limit value 0.15ppm
occurrence method
irradiation method, electrolysis method, radiochemical method and other
special
strong oxidation


profile

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properties

ozone,The chemical molecular formula is O3,also known as three-atomic oxygen and superoxygen, which is named for its fishy odor and can be reduced to oxygen at room temperature. Higher specific gravity than oxygen, easily soluble in water, easy to decompose.  Because ozone is composed of oxygen molecules carrying an oxygen atom, it is only a temporary state, carrying oxygen atoms in addition to oxidation, the rest of the combination of oxygen into a stable state, so ozone has no secondary pollution.   [2] 
Liquid ozone is dark blue with a density of 1.614g/cm3(liquid,-185.4℃) and a boiling point of -111.9℃, while solid ozone is blue-black with a melting point of -192.7℃.  The molecule is V-shaped and unstable.  The decomposition of ozone is slow at room temperature, and it is accelerated to decompose into oxygen when the ozone is irradiated with ultraviolet light of 25nm or above 164℃ or in the presence of catalyst.  [1]  Under normal temperature and pressure, ozone is a gas with a critical temperature of -12.1℃ and a critical pressure of 5.31MPa.  It is light blue when gaseous, dark blue when liquefied, and purple-black when solid.  Gas is insoluble in water and liquid oxygen, but soluble in liquid nitrogen and lye.  Liquid ozone slowly decomposes at room temperature, rapidly decomposes at high temperature, producing oxygen, and can explode when hit or friction occurs.  [3] 
The decomposition rate of ozone in aqueous solution is faster than that in gas phase.  The half-life of ozone decomposition in water is related to temperature and pH value.  As the temperature increases, the decomposition rate increases.  When the temperature exceeds 100℃, the decomposition is violent;  When the temperature reaches 270℃, it can be converted into oxygen immediately.  The higher the pH, the faster the breakdown.  It is decomposed in the air of normal temperature and pressure, and the half-life is about 15 ~ 30min.  [4] 
the olfactory threshold of ozone is 0.02mL/m3,If the concentration of ozone reaches 0.1mL/m3it will stimulate the mucosa, and if the concentration reaches 2mL/m3it will cause central nervous disorders. [3] 

Strong oxidizing

ozone can discolor most organic pigments.  Can slowly erode rubber, cork, so that organic unsaturated compounds are oxidized.  Commonly used in: beverage disinfection and sterilization, air purification, bleaching, water treatment and drinking water disinfection, granary killing mold and eggs;  In reaction with organic unsaturated compounds, ozonides can be formed, which can be decomposed in the presence of water, and the original unsaturated bonds can be opened to produce aldehydes, ketonesandcarboxylic acids etc.Because of ozone decomposition, it can be used as a synthetic method and determine the structure of organic matter.  [3] 
Ozone is one of the strongest oxidants in nature because of its strong oxidability and bactericidal properties. Its REDOX potential in water is second only to fluorine.  At the same time, the product of ozone reaction is oxygen, so ozone is an efficient oxidant without secondary pollution.  As a strong oxidant, its characteristics are as follows  [5]  :①can be used for selective oxidation, high yield of the main product; ② The oxidation temperature is low, and the oxidation ability is strong at atmospheric pressure, and it is beneficial to the oxidation of sensitive substances;③ The reaction speed is fast and can be quantitatively oxidized;  ④ Easy to use and manufacture.  [5] 
The application of ozone is based on its strong oxidizing ability and bactericidal ability.  The application of ozone according to its role classification, can be divided into: sterilization, decolorization, deodorization, deodorization and oxidation decomposition.  According to its application field, it is mainly applied in the following fields: water treatment;  Food processing, storage, preservation;  Household appliances;  Health care;  Chemical oxidation.   [5] 

检测分析

Detection and analysis Ozone analysis mainly includes spectral analysis and electrochemical analysis.  The common detection methods are iodine quantity method, indigo disulfonic acid sodium spectrophotometry, ultraviolet absorption method and chemiluminescence method.  Iodimetry is commonly used in laboratories.  By passing ozone into a solution of potassium iodide, iodine can be freed, and this reaction can be used for the quantitative analysis of ozone.  [3] 
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Iodinometric method uses ozone and KI to generate I2, takes starch as indicator,titrates with sodium thiosulfate, or can use starch reagent after color development, according to the color depth, colorimetric determination at 550nm.  [4] 

A brief history

As early as 1785, the German physicist von Marum, experimenting with a high-powered motor, discovered that when air flows over a string of sparks, it produces a special smell, but did not investigate it.  Later, in 1840, Schaubein also discovered a unique odor during electrolysis and spark discharge experiments and concluded that it was produced by a new gas, thus announcing the discovery of ozone. [6] 
During World War I, ozone was first used by some German soldiers to treat skin gangrene caused by anaerobic bacteria.  In 1936, the French doctor P. Ubourg first advocated injecting ozone into the rectum to treat colitis.  Since then, medical researchers and medical workers have made rapid progress in the clinical application of ozone.  Ozone in foreign countries, especially in Europe has a long history of more than 50 years of clinical application, after the ninety s, the application of ozone into our country, mainly applies the ozone treatment between the waist dish outstanding, scavenging free radicals, anti-aging and so on, after ozone quickly developed in clinical application and is becoming a widely used, powerful new drugs, the new method.  [7] 
From the early 1980s, China has begun to pay attention to the ozone disinfection of drinking water and the depth treatment of industrial wastewater, but the development is slower.  In our present urban water supply, the vast majority of water plants adopt the treatment process of coagulation, precipitation, filtration and disinfection, which mainly uses chlorine gas and bleaching powder, the proportion of using ozone is very low.  At the same time, the application of ozone in cooling water treatment practice is just beginning.  However, due to the economic efficiency, reliability, absolute non-toxic, no secondary pollution and other advantages of ozone treatment, it can be predicted that ozone will be popularized in our country.   [5] 

Generation methods

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Ozone generation methods mainly include ultraviolet irradiation method, electrolysis method, radiochemical method and dielectric barrier discharge method.

Ultraviolet irradiation

is the use of ultraviolet light irradiation dry oxygen, so that a part of the oxygen molecules are activated to dissociate into oxygen atoms, thus forming ozone.Ozone produced by ultraviolet irradiation is characterized by low concentration of ozone, the advantage is not easy to produce oxides, do not need complex conversion equipment.  But UV irradiation is not suitable for mass production of ozone, only suitable for a small number of low concentration requirements of various tests, such as air disinfection, sterilization, deodorization and so on.

Electrolytic process

The technology of ozone preparation by electrolysis was established in 1840. It mainly uses low voltage direct current to electrolyze water, which produces ozone by oxidizing water at the anode-solution interface. The ozone preparation device is composed of electrolyte solution and Yin and Yang poles.  Ozone precipitates at the anode, and the cathode can be divided into two types: hydrogen evolution cathode and oxygen reduction cathode.  [8]  Before the 1980s, electrolytes were mostly added with acid and salt electrolytes in water, with a relatively small electrolytic area, low ozone production and high operating costs.  After a lot of research on plate material, electrolyte, mechanism and process of electrolysis, ozone technology by electrolysis has made great progress.Recently developed SPE (solid polymer electrolyte) electrode and metal oxidation catalytic technology, electrolyzed purified water to obtain more than 14% high concentration of ozone.  Ozone produced by electrolysis has high concentration, pure composition, high solubility in water [5]  , no pretreatment of feed air and no nitrogen oxides;  In addition, the ozone production equipment is small and light, simple structure, no noise, portable, so its application prospect is very broad.  [8]   Its main disadvantage is its high energy consumption. After further improvement and efforts to reduce the cost and power consumption, it may be competitive with the widely used dielectric barrier discharge method.  [5] 
Among the methods for preparing ozone by electrolysis, the method using lead dioxide as electrode is the main one. How to improve the efficiency of ozone production by electrolysis is the main research direction.  As we know, in the electrochemical reaction, pH, temperature, current density and the types of electrode is the most critical, now there are a lot of literature reports on modification of lead dioxide electrode, such as in the lead dioxide electrode with a small amount of titanium dioxide, can greatly improve the efficiency of lead dioxide electrode current and electrical conductivity, but failed to change the lead dioxide corrosion problems;  The β-type lead dioxide is more stable and affordable, and the ozone concentration can reach more than 13%, while it does not produce harmful nitrogen oxides.  However, β-type lead dioxide is easy to recrystallize under high voltage and acid conditions, resulting in unstable catalytic efficiency of the anode catalytic layer.  The anode and cathode catalytic layer is easy to desorption, which makes the working life of the membrane electrode very short, and even leads to short circuit in serious cases.  The existing preparation technology of the membrane electrode catalytic layer is not stable, and the main reason for this problem is that the catalytic layer is not closely attached to the membrane.  Based on the advantages and disadvantages of lead dioxide and SPE membrane electrode, it is necessary to study the composite membrane electrode of lead dioxide and SPE.  [8] 

Radiochemistry

Radiochemistry uses nuclear radiation from various sources to dissociate oxygen molecules into ozone.  Two kinds of processes have been used in industrial ozone production. The first is the contact of oxygen with fission products and the thermal collision of oxygen with fission products and secondary radiation to produce ozone.  Second, ozone is generated only under radiation. Because of the high cost and poor safety of using radioactive sources, this method is only suitable for some special cases and is not suitable for industrial mass production. [5] 

Dielectric barrier discharge method

is also known as silent discharge method (DBD method). The corona is generated in the gas by alternating high voltage electric field, and the free energetic electrons in the corona dissociate oxygen molecules, which are aggregated into ozone molecules by collision.  Dielectric barrier discharge method has the advantages of relatively low energy consumption, large ozone production per unit, dry air, oxygen or oxygen-rich gas with high concentration of oxygen can be used as the gas source, so this method is mostly used in industrial ozone synthesis.  [5] 
In the last century, ozone was usually produced by thermochemical methods.  Although the theoretical value of ozone rate (energy utilization efficiency of ozone production) calculated by thermochemical theory is 1200g/ (kW·h), only 4% ~ 12% conversion ratio is available in practical production.  The remaining energy is converted into heat and escapes, and the actual yield is far from the theoretical value. Since the 21st century, in order to improve the concentration and yield of ozone in sealed containers, so as to reduce the production cost, scientists have carried out numerous academic exchanges.  [9]   With the continuous theoretical research and the continuous improvement of technology, the main research directions are focused on different raw materials, related gases, different electrode forms, different reaction media, electrode materials and discharge forms.  [9] 
Plasma The basic principle of ozone generation in the process of plasma discharge is that in the low-temperature plasma atmosphere formed by oxygen-containing gas in the discharge reactor, free electrons of a certain energy decompose oxygen molecules into oxygen atoms, and then form ozone molecules through three-body collision reaction, and ozone decomposition reaction occurs at the same time.  [9] 

Ozone disinfection technology and application

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Ozone disinfection technology and application edit the advantages of ozone disinfection

(1)disinfection has no dead Angle, high sterilization efficiency and odor removal.  During disinfection, the ozone generator produces a certain amount of ozone, which has uniform diffusion and good permeability in a relatively closed environment. It overcomes the problem of the disinfection dead Angle in ultraviolet sterilization, and achieves the purpose of all-round, rapid and efficient sterilization.  In addition, because of its wide bactericidal spectrum, it can kill a variety of microorganisms such as bacterial reproductive body, spore, virus, fungus and protozoan sporulation, and can also destroy botulinum bacillus and toxin and rickettsii body etc. and also has a strong function of odor such as mildew, fishy and smelly.  [2] 
(2)No residue, no pollution.  Ozone is produced by using the oxygen in the air. In the process of disinfection and oxidation, the excess oxygen atoms combine into molecular oxygen after 30 minutes, and there is no residual substance, which solves the problem of secondary pollution caused by the residue of disinfectant disinfection and eliminates the need for cleaning again after the end of disinfection.  [2] 

Disinfection

Ozone is a strong oxidant, its molecules are extremely unstable, can decompose to produce monatomic oxygen (O) and hydroxyl (OH) with strong oxidation capacity, is a unique melt-type preparation, can quickly integrate into the cell wall, damage the internal structure of bacteria, viruses and other microorganisms, has a strong killing effect on various pathogenic microorganisms.  The sterilization process is a biochemical oxidation reaction.  Its effects are mainly achieved through the following three forms :(1) ozone can oxidize and decompose the enzymes needed for glucose in bacteria, so that bacteria are inactivated and die;  (2) Acting on nuclear substances in bacterial cells, such as purines and pyrimidines in nucleic acids, destroying their organelles, DNA and RNA, thus damaging the metabolism of bacteria and leading to the death of bacteria;  (3) Ozone reacts with lipids in the bacterial cell wall, penetrates the cell membrane, invades the cell, acts on lipoproteins in the outer membrane and lipopolysaccharides in the inner membrane, and causes permeability distortion of bacteria and dissolution and death;  [7]  (4)Ozone acts on the four polypeptide chains of the capsid protein of the virus and damages the RNA, destroying the protein that forms it.  After the phage is oxidized by ozone, its epidermis is broken into many fragments, from which a lot of ribonucleic acid is released, which interferes with its adsorption to the host.   [2] 
The effects of ozone are mainly concentrated in five aspects: anti-inflammation and anti-infection, pain relief, oxidation cholesterol , improvement of body immunity, and oxygen supply to ischemic tissue.  But because the molecular structure of ozone is a special molecule composed of three oxygen atoms, although it has strong oxidation, but it is also very unstable, under normal temperature and pressure, it will automatically reduce to oxygen after 20 minutes.  Therefore, the clinical application of ozone is now used to make, commonly used ozone generator.  Its generation principle can be obtained by high-voltage discharge, corona discharge, electrochemistry, photochemistry, atomic radiation and other methods. The principle is to use high-voltage electric power or chemical reaction to make part of the oxygen in the air decompose and polymerize into ozone, which is a process of oxygen allotrope transformation.  After making ozone, it can be dissolved in sterilized water, blood, body fluids, or directly acted on tissues to achieve different therapeutic purposes. [7] 

The clinical application

ozone has developed from the initial treatment of colitis and skin gangrene to today's treatment of cerebral stroke, rheumatic diseases, joint diseases, disc herniation, anti-free radical anti-aging, acute and chronic hepatitis, prostatitis, chronic wounds caused by pressure ulcers, vaginitis and so on.  However, the treatment effect, operation technology, promotion and application are mainly reflected in the following aspects:   [7] 
The treatment of disc
herniation is the most widely used in clinical practice, and the relatively mature technology is the treatment of cervical and lumbar disc herniation.  Now commonly used percutaneous laser vaporization decompression combined interventional treatment of ozone, with curved needle technique under local anesthesia, during laser vaporization to constantly adjust the needle position, until the ideal location, in the laser optical fiber, two vaporization, the vaporization, to a certain concentration of 50 ug/ml) (ozone injection of intervertebral disc and vertebral side clearance with a syringe, so as to achieve anti-inflammatory,  Pain relief and other effects.  This method is not easy to relapse after treatment, and there are no side effects to patients. It is a new technology adopted by hospitals one after another.  [7] 
Treatment of viral liver disease
ozone in the treatment of acute and chronic viral hepatitis is also significant.  Patient OF VIRUS virus HEPATITIS SUFFERS VIRUS TO ENCROACH AS A RESULT OF HEPATOCYTE, PRODUCE INFLAMMATORY REACTION SUCH AS OEDEMA, denATURATION, OZONE IS A KIND OF STRONG oxidANT, CAN MAKE THE RNA OF VIRUS denATURATION QUICKLY, THE METABOLISM OF BACTERIUM STOPS, ACCORDINGLY, HAVE antiINFLAMMATORY EFFECT. [7] 
Ozone is used to treat viral hepatitis because it also boosts immunity and induces the production of cytokines that protect the liver. Research data also show that ozone treatment can quickly reduce the patient's body transaminase, can be yellowing, but also can reduce the level of virus in the body, inhibit virus replication, is a new treatment without toxic side effects. In 2000, ozone treatment of viral hepatitis was approved for clinical use in Europe, and in 2004, this technology was approved for clinical use in China. [7] 
Treatment of ischemic and hypoxic diseases
Tylicki et al. reported that 12 hemodialysis patients with arteriosclerosis complicated with lower extremity arterial thrombosis were treated with high pressure ozone for 9 times. As a result, total cholesterol decreased by 8.34% on average, low density lipoprotein decreased by 17.9% on average, while factor VIII activity did not show significant changes.  This indicates that this method does not harm the vascular endothelial system of patients, and the reduction of total cholesterol and low-density lipoprotein is conducive to the improvement of lower limb arteriosclerosis.  [7] 
In China, ozone has been used to treat gynecological infections, such as candida vaginitis;  It has also been reported that ozone water washing combined with microwave was used to treat chronic cervicitis, ozone autoblood therapy was applied to patients with bronchial asthma and achieved good curative effect, and ozone was used to treat wound healing caused by burns, and the effect was very significant.  [7] 
Although ozone has been used in clinical practice for less than 50 years, it has shown its advantages in many aspects and is gradually replacing some traditional treatment methods.  In 1999, Italy initiated and established the International Medical Ozone Association (IMOS) with the main purpose of promoting basic research and clinical application of ozone, and providing clinical standards for the treatment of ozone.  [7] 
At present, the association is working with a large number of medical workers to find new methods and directions for the clinical application of ozone. For example, in the treatment of lumbar disc herniation, multi-approach puncture approach, combination of ozone technology and collagenase technology, and double-needle technology are considered.  It is believed that there will soon be more and better ozone new technology applied in clinical, for more and more patients to bring good news.  From this point of view, ozone development prospects should be very broad.  However, there are also contraindications in the clinical application of ozone. [7] 
First, ozone cannot be absorbed directly into the lungs, because direct inhalation will cause damage to alveolar epithelial cells.  Secondly, patients with faba bean disease can not be ozone blood therapy;  Third, ozone treatment causes very few allergic reactions;  Fourthly, in the treatment of ozone, excessive concentration and dose will cause toxic reaction.  [7] 

Vegetable disease control

The use of ozone to control vegetable diseases has long been studied abroad, and relevant reports have been reported in China in recent years.  All air-borne diseases and most soil-borne diseases of fruit and vegetable crops such as cucumber, green pepper and eggplant can be controlled with low quality fraction of ozone produced by greenhouse plant disease ozone control equipment.  Low quality fraction of ozone can effectively prevent the occurrence of cucumber downy mildew, POWdery mildew, anthracnose, leaf blight, Mosaic virus, eggplant, bean gray mold also has a preventive effect.  In addition to the remarkable control effect on diseases, ozone also has the control effect on some insect pests, such as the control rate of aphids reached 63% ~ 68%. [10] 

Removing Pesticide Residues from vegetables

One of the biggest concerns when eating vegetables is pesticide residues.  Although agricultural administrative departments have developed many measures to reduce pesticide residues, emphasizing the rational use of pesticides, advocating the use of biological pesticides and high efficiency, low toxicity, low residue pesticides, there are still often pesticide poisoning events in vegetables.  Traditional methods to remove pesticide residues include soaking and washing, soaking in alkaline water, peeling, storage, heating and so on.  Dr. Pan Canping of China Agricultural University pointed out that the traditional method of water immersion can hardly remove the pesticide residues of fruits and vegetables, but the high concentration of ozone immersion can effectively remove the pesticide residues.  Studies have shown that ozone can effectively degrade pesticides on bean sprouts when they are cultivated with ozone.  The bean sprouts were soaked in 3mg/L ozonated water for 30min and then cultured for 8h. The pesticides on the sprouts were degraded as follows: Cremydan 100%, diazinon 76%, dichlorvos 96%.  The pesticide residues of chlorothalonil, Dimethoate, trichlorfon and dichlorvos on vegetables treated with ozone reached the international permissible standard.  [10] 

Fresh-keeping processing vegetables

Wash and disinfect vegetables
by using the oxidation and bactericidal effects of ozone, using ozonated water to clean fruits and vegetables can not only effectively kill pathogenic bacteria and spoilage bacteria attached to the surface of vegetables, but also remove other toxic substances remaining on the surface of vegetables.  It is one of the ways to maintain and improve the safety of new vegetable food.  The results showed that this method could reduce the total number of bacteria on the surface of fruits and vegetables by more than 90%, especially the killing effect of Escherichia coli was particularly obvious.  [10] 
Fresh-cut vegetables
Western developed countries began to study and produce fresh-cut vegetables as early as the 1950s, and have now formed a complete, advanced and systematic processing system.  With the rapid development of people's life and the improvement of the understanding of food safety, fresh cut vegetables have become increasingly popular in China. However, at present, the fresh-cut vegetables sold in general supermarkets are mostly processed by simple cleaning, cutting and other rough processing, and lack of advanced purification processing technology. Consumers still have concerns in their hearts, and their safety and health are still questioned.  Ozone has a good killing effect on the microorganisms on the surface of vegetables, and its oxidation ability can oxidize and destroy the injured ethylene produced by fruits and vegetables, which has an ideal effect on delaying the ripening of vegetables and maintaining the fresh quality of vegetables.  Recently, the application of ozone in fresh cut vegetables at home and abroad were reviewed and the research, some studies have shown that the ozone water to immerse, not only can significantly reduce the fresh cut vegetables on the surface of the microbe, improve the safety of products in the field of microbiology, also can obviously inhibit the fresh cut vegetables in the degradation of chlorophyll, has inhibitory effect on the activity of polyphenol oxidase, protect the vitamin C,  But it may have a certain oxidation effect on reducing sugar.  [10] 
Storage of vegetables
Vegetables are still living organisms after harvesting, and respiration is one of the most important physiological activities after harvesting.  If respiration is inhibited, the freshness of vegetables can be prolonged.  Many experiments have shown that ozone can obviously inhibit the respiration of vegetables in storage.  The principle is that vegetables release ethylene easily during storage, and ozone can be oxidized to remove ethylene, thereby slowing down the metabolism of fruits and vegetables.  In addition, ozone can also destroy the foul odor of organic matter or inorganic matter, has the function of deodorization and air purification, so it can be used for the disinfection of vegetable storage environment and maintain the environment conducive to the maintenance of vegetable vitality. [10] 
Desalting salted vegetables
vegetables are prone to eat too much in peak season, and not enough to eat in off-season.  People usually make some vegetables into pickles and salted vegetables.  Such as pickled mustard, snow vegetables, radish and so on are the main pickled vegetables, in the curing process, generally use 8% to 15%, or even higher concentration of salt for curing, resulting in too salty taste, can not be eaten directly, and may even appear salt poisoning.  Therefore, salted vegetables need to be eaten after desalting. The traditional desalting method uses tap water to soak. After desalting, microorganisms proliferate in large numbers, especially in summer, which is prone to long film, flowers and soft.  Ozone has the characteristics of killing a variety of microorganisms, studies have shown that the use of ozone immersion for desalination of salted vegetables, compared with water immersion treatment of salted vegetables, the number of microorganisms significantly decreased.  [10] 

臭氧氧化技术及应用

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氧化机理

臭氧具有的强氧化性是因为臭氧分子中氧原子具有强亲电子或亲质子性。臭氧分解后产生新生态氧原子,在水中可形成具有强氧化作用基团-羟基自由基,可快速除去废水中的有机污染物,而自身分解为氧,不会造成二次污染。 [4] 
目前认为臭氧与有机物的反应有2种途径:
(1) 臭氧以氧分子形式与水体中的有机物直接反应。 [4] 
该方法选择性较强,一般攻击带有双键的有机物,对芳香烃类和不饱和脂肪烃有机化合物的效果更好。 [4] 
(2) 碱性条件下臭氧在水体中分解后产生氧化性很强的羟基自由基等中间产物,羟基自由基与有机化合物发生氧化反应。 [4] 
该氧化方式无选择性。 [4] 

废水处理

臭氧氧化技术用于废水处理有如下2种情况:(1)臭氧作为预处理或后处理,与其他方法联合使用,如絮凝+臭氧、臭氧+生物滤池(生物活性炭法等)、臭氧+膜处理;(2)臭氧自身氧化处理,如:臭氧、臭氧-双氧水、臭氧-双氧水/UV光氧化、臭氧/UV光氧化、臭氧-固体催化剂(固体催化剂如活性炭等)。 [4] 
混凝 - 臭氧氧化技术
混凝-臭氧氧化技术是在投加混凝剂条件下,利用臭氧氧化技术处理废水。臭氧能改变水中悬浮物的性质,从而改变混凝操作单元去除效果,此方法可使水中悬浮颗粒变大,使处于溶解状态的有机物变成可混凝胶体颗粒,从而减少混凝剂投加量,降低化学药剂耗量。 [4] 
臭氧 - 生化法
利用臭氧催化氧化联合生物活性炭滤池处理废水专利近几年有较多报道,统称为利用臭氧预处理废水,破坏水中难降解有机物,提高可生化性,再利用活性炭生物滤池进一步处理的技术。该技术充分利用了臭氧的强氧化性、也利用了生物滤池的成本优势,两者结合后处理效果良好。 [4] 
臭氧-膜处理技术
有专利公布了一种臭氧催化氧化-陶瓷膜过滤深度处理焦化废水系统,通过臭氧催化氧化与陶瓷膜分离联用实现了粉末催化剂在动态反应器中的应用。 [4] 
反应系统确保在单一反应器中分段进行臭氧氧化和催化臭氧氧化,降低了单独臭氧氧化和催化臭氧氧化过程中的传质阻力,提高了羟基自由基利用率和有机物去除率,最终实现了焦化废水深度处理出水COD、色度和浊度达标。 [4] 
臭氧直接曝气处理
采取二级生化出水经两级臭氧催化氧化处理方法,即一级臭氧催化氧化池底部与二级臭氧催化氧化池相连,二级臭氧催化氧化池设有总出水口,实现节能和降低成本。能提高COD去除率20%。 [4] 
有专利公布了一种降低有机胺废水中COD浓度的臭氧处理系统,利用臭氧氧化来降低有机胺废水COD。该系统将臭氧反应池分为前、中、后3个接触氧化反应池,分别用隔板进行分割,且3个接触氧化池体积依次减小。利用该法接触氧化地进行氧化处理,来实现含有机胺废水的治理,达到排放标准。 [4] 
臭氧-双氧水联合氧化作用
臭氧-双氧水系统是污水处理的一种高级氧化方法。臭氧和过氧化氢协同作用可以产生具有极强氧化作用的羟基自由基,能有效去除水中的有机污染物。机理显示加入过氧化氢会促进羟基自由基生成,同时pH值影响也很明显。过氧化氢阴离子浓度是影响羟基自由基生成的关键因素,而pH值对过氧化氢阴离子浓度也有较大影响,所以pH值是影响反应的重要条件;同时,臭氧-双氧水比例也是影响有机污染物去除效果的关键因素。此外,臭氧 - 双氧水工艺对于去除天然水体中的有机污染物也很有效。 [4] 
臭氧-双氧水-UV光氧化
氧化联合催化氧化技术UV光氧化-臭氧法是将臭氧与紫外光辐射相结合的一种高级氧化过程,始于1970年。臭氧-双氧水-UV光氧化法对处理难氧化物质比较有效,可使氧化速度提高10~10000倍。 [4] 
UV光氧化-臭氧法中的氧化反应为自由基型,即液相臭氧在紫外光辐射下分解产生·OH自由基,由·OH自由基与水中的溶解物进行反应。 [4] 
臭氧 - 固体催化剂技术
臭氧-固体催化剂技术固体催化剂包括活性炭、金属及其氧化物。臭氧/活性炭联用体系能显著提高COD、TOC去除率,且显示出良好的协同作用,实现难降解制药有机废水可生化性改善。活性炭吸附-催化臭氧氧化技术对苯乙酮的去除率随臭氧进气量、活性炭投加量增加而提高,在最优工艺条件下,苯乙酮去除率可达92.3%。 [4] 
臭氧氧化处理废水,无论是臭氧-紫外组合,还是臭氧-双氧水协同催化氧化技术,本质都是羟基自由基氧化降解废水中的各类污染物,不形成二次污染,在废水处理中应用前景广阔。
目前影响臭氧高级氧化技术应用的主要问题是臭氧利用率低。 [4]  臭氧在各类废水处理领域的研究和应用日益增多。臭氧技术在处理废水方面具有氧化性强、原料制备廉价易得、能处理多种污染物、反应后不出现二次污染等特点。臭氧虽然能氧化水中许多难降解有机物,但不易将有机物彻底分解为CO2和H2O,其产物常常为羧酸类易于生物降解有机物,如:一元醛、二元醛、醛酸、一元羧酸、二元羧酸类有机小分子,因此,在大多数情况下,臭氧更适宜于和其它净化技术配合使用来达到最终的废水处理目标。 [11] 

烟气净化

臭氧应用于烟气净化领域具有广阔的前景:(1)臭氧是一种清洁氧化剂,不会产生二次污染物;(2)它能够在良好的脱硫脱硝的基础上,同时实现对汞的高效去除;(3)臭氧对烟气中氯化物、氟化物、VOCS以及二噁英也有一定的去除能力,它对多种污染物的协同脱除能力是应用到实际过程中最有利的优点。 [12]  尽管臭氧法是烟气净化领域高效的污染控制方法,但现阶段臭氧的制备成本较高,应用技术不够成熟,限制了该技术的广泛推广使用,因此,高效、节能、环保的臭氧发生装置仍是臭氧法运用的关键。 [12] 

危害

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对人体危害

国际环境空气质量标准(National Ambient Air Quality Standards,NAAQS)提出,人在一个小时内可接受臭氧的极限浓度是260μg/m3。 在320μg/m3臭氧环境中活动1h就会引起咳嗽、呼吸困难及肺功能下降。臭氧还能参与生物体中的不饱和脂肪酸、氨基及其他蛋白质反应,使长时间直接接触高浓度臭氧的人出现疲乏、咳嗽、胸闷胸痛、皮肤起皱、恶心头痛、脉搏加速、记忆力衰退、视力下降等症状。 [13] 

其他危害

臭氧也会使植物叶子变黄甚至枯萎,对植物造成损害,甚至造成农林植物的减产、经济效益下降等。臭氧能够较快地与室内的建筑材料(如乳胶涂料等表面涂层)、居家用品(如软木器具、地毯等)、丝、棉花、醋酸纤维素、 尼龙和聚酯的制成品中含不饱和碳碳键的有机化合物(包括橡胶、 苯乙烯、不饱和脂肪酸及其酯类)发生反应,从而造成染料褪色、照片图像层脱色、轮胎老化等。 [13] 

臭氧污染防治

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臭氧污染来源

臭氧的来源分为自然源和人为源 。自然源的臭氧主要指平流层的下传。1962年,Junge研究认为,在波长小于240nm 紫外线的辐射条件下,平流层中的臭氧会分解,产生的氧原子与氧分子结合产生臭氧,平流层臭氧向下传输到对流层,成为对流层中臭氧的源。 [13] 
人为源的臭氧主要是由人为排放的NOx、VOCs等污染物的光化学反应生成。在晴天、紫外线辐射强的条件下,NO2等发生光解生成一氧化氮和氧原子,氧原子与氧反应生成臭氧。臭氧是强氧化剂,在洁净大气中,臭氧与一氧化氮反应生成为NO2,而臭氧分解为氧气,上述反应的存在使臭氧在大气中达到一种平衡状态,不会造成臭氧累积。当空气中存在大量VOCs等污染物时,VOCs等产生的自由基与一氧化氮反应生成二氧化氮,此反应与臭氧和一氧化氮的反应形成竞争,不断取代消耗二氧化氮光解产生的NO,HO2、RO2、H、OH引起了NO向NO2转化,使上述动态平衡遭到破坏,导致臭氧逐渐累积,达到污染难度级别 [14]  。NOx、VOCs、CO等臭氧前体物都是一次污染物,主要来源于交通工具的尾气排放、石油化工和火力发电等工业污染源排放及饮食、印刷、房地产等行业的污染源排放等。秸秆等生物质的大量燃烧,也会产生大量的VOCs和NOx等臭氧前体物。 [13] 

臭氧污染监测

我国2012年2月发布的《环境空气质量标准》(GB3095-2012)规定,臭氧的日最大8小时平均值二级浓度限值为160μg/m3。作为空气中六大污染物之一,臭氧污染监测是臭氧污染预报和防治的重要内容之一。1929年Dobson分光光度计的研制成功,奠定了大气臭氧地面观测的基础。我国在20世纪50年代开始对臭氧总含量进行观测,先后建立了香河市臭氧观测站和昆明臭氧观测站,所用仪器均为Dobson臭氧分光光度计。测定臭氧的方法有试纸比色法、微分光谱法、库仑法、极谱法、气相色谱法、化学发光及荧光法等十几种。 [13] 
我国目前测定臭氧的标准方法主要有《环境空气臭氧的测定 靛蓝二磺酸钠分光光度法》(HJ 504-2009)和《环境空气臭氧的测定 紫外光度法》(HJ 590-2010)两种手工分析方法,自动监测方法主要有紫外荧光法和差分吸收光谱分析法。 [13] 
“十二五”末,我国建成国家环境空气质量监测网。国家环境空气质量监测网由城市站、区域站和背景站组,监测内容包括SO2、NO2、PM10、PM2.5、O3和CO等6项监测指标的实时小时浓度值、日均浓度值等,可以实时掌握监测点的臭氧指标数据,摸清重点区域污染特征,提高空气质量预报预警能力。2013年7月30日发布的《环境空气气态污染物连续自动监测系统技术要求及检测方法》(HJ 654-2013),规定了环境空气气态污染物连续自动监测系统的组成、技术要求、性能指标和检测方法。之后又陆续发布《环境空气自动监测标准传递管理规定(试行)》(环办监测函〔2017〕242号)和《国家环境空气质量监测网城市站运行管理实施细则》(环办监测函〔2017〕290号)。2017年10月17日,环境保护部又发布《环境空气臭氧一级校准作业指导书(试行)》《环境空气臭氧标准参考光度计间接比对作业指导书(试行)》《环境空气臭氧传递标准间逐级校准作业指导书(试行)》《环境空气臭氧自动监测现场比对核查作业指导书(试行)》4项涉及臭氧监测的作业指导书,完善了全国臭氧监测质量管控体系,并将对臭氧进行统一标准定期监督检查。 [13] 
2018年2月22日,为贯彻落实《2018年重点地区环境空气挥发性有机物监测方案》,生态环境部发布了《环境空气臭氧前体有机物手工监测技术要求(试行)》(环办监测函〔2018〕240号),进一步规范环境空气臭氧前体有机物手工监测工作。 [13] 

臭氧的预报

早在20世纪70年代,欧洲就建立了中期天气预报平台(ECMWF)。1979年,欧洲第一次成功发布了中期数值预报。在20世纪末,中国科学院大气物理所建立了“城市空气质量数值预报模拟系统”,并对天津、沈阳等市空气污染物进行了数值预报。2007年12月16日,上海气象台首次发布每日臭氧预报。当时,为评估大气环境对生态和人类健康的影响,欧美国家都已经开展了类似预报,其中臭氧预报是天气预报的主要产品之一。 [13] 
随着臭氧污染程度的加重以及人们对臭氧危害认识的加深,对臭氧的准确预报显得尤为重要。上海、广东等省市已连续多年开展臭氧预报。2018年1月16日,中国气象局负责人表示,2018年将开展全国臭氧气象预报,为生态环境部门提供支撑。 [13] 

控制对策

我国对于臭氧污染的控制防治尚处于起步阶段。臭氧污染与雾霾不同,其产生机制复杂,治理难度很大。在公众层面,不仅要注意个人健康防护,而且应积极参与到臭氧防治工作。臭氧污染时,戴口罩基本阻挡不了臭氧的吸入。因此,在臭氧污染严重时,儿童和老人等敏感人群应尽量避免在午后日照强烈时外出,远离马路边、装修污染严重的地方。在国家层面,目前主要要建立臭氧和PM2.5协同控制机制,制定行之有效的臭氧污染防治对策。 [13] 
挥发性有机化合污染物和氮氧化物是臭氧形成的重要前体物,控制臭氧污染,就要协同控制好挥发性有机化合物和氮氧化物的排放。如:使用天然气、太阳能、风能、生物质能等清洁能源,整治各类散乱污企业,限制煤炭等的消费总量;优化发展方式,改进工艺设计,在火电、钢铁、水泥建材、焦化、有色、石油炼制、化工、农药医药、包装印刷等重点行业实施清洁生产,减少污染物排放;控制城市机动车数量,进一步严格尾气排放标准,鼓励购买和使用清洁能源汽车,减少机动车尾气排放量。按《大气污染防治行动计划》,通过采取综合防治措施,坚持政府调控与市场调节相结合、全面推进与重点突破相配合、区域协作与属地管理相协调、总量减排与质量改善相同步,形成政府统领、企业施治、市场驱动、公众参与的大气污染防治新机制。