What is Ozone?

Chemical formula O ₃ , formula 47.998, an allotropic form of oxygen element. Light blue gas with fishy smell. Ozone is strongly oxidizing and is a stronger oxidant than oxygen. Oxidation can occur at lower temperatures. For example, it can oxidize silver to silver peroxide, oxidize lead sulfide to lead sulfate, and react with potassium iodide to generate iodine. Turpentine and gas can spontaneously ignite in ozone. Ozone is a powerful bleaching agent in the presence of water. With unsaturated organic compounds, odor oxides are also easily generated at low temperatures. Used as strong oxidant, bleach, fur deodorant, air purifier, disinfectant, disinfection and deodorization of drinking water. In chemical production, ozone can be used to replace many catalytic oxidations or high-temperature oxidations, simplifying production processes and increasing productivity. Liquid ozone can also be used as an oxidant for rocket fuel. Existing in the atmosphere, the concentration near the surface of the earth is 0.001 0.03ppm. It is generated by the oxygen in the atmosphere after absorbing the ultraviolet rays of the sun with a wavelength less than 185nm. This ozone layer can absorb short-wave (below 30nm) rays harmful to the human body in sunlight. Prevent this short-wave light from hitting the ground and protect human beings from ultraviolet rays. ^[1]

Chinese name: ozone
English name: Ozone
nickname: Superoxide
Chemical formula: O
Molecular weight: 47.9982
CAS Registry Number: 10028-15-6
EINECS registration number: 233-069-2
Melting point: -192

Boiling point: -111
Water soluble: 1 volume of water dissolves 0.494 volume of ozone
Density: 2.14g / L (0 ° C, 0.1MPa)
Exterior: Blue gas at room temperature
Application: Used in medicine, agriculture, catering industry, sterilization, formaldehyde removal, etc.
Security description: Workplace limit 0.15ppm
Method of occurrence: Irradiation method, electrolytic method, radiochemical method, etc.
Features: Strong oxidizing

Introduction to Ozone

Ozone Basic Properties

Ozone, chemical formula is O ₃ , also known as triatomic oxygen, super oxygen, because of its fish-like odor, it can be reduced to oxygen by itself at normal temperature. The specific gravity is larger than that of oxygen, easily soluble in water, and easily decomposed. Ozone is composed of an oxygen molecule carrying an oxygen atom, which determines that it is only a temporary storage state. Except for the oxidation oxygen used, the remaining oxygen is combined into oxygen into a stable state, so there is no secondary pollution of ozone. ^[2]

Liquid ozone is dark blue, density is 1.614g / cm ³ (liquid, -185.4 ° C), boiling point is -111.9 ° C, solid ozone is blue-black, and melting point is -192.7 ° C. The molecule is V-shaped and unstable. It decomposes slowly at normal temperature, and accelerates to decompose into oxygen when it is above 164 or when a catalyst is present or when irradiating ozone with ultraviolet rays with a wavelength of about 25nm. ^[1] Ozone is a gas at normal temperature and pressure, and its critical temperature is -12.1 ° C and its critical pressure is 5.31 MPa. It is light blue in gaseous state, dark blue after liquefaction, and purple-black in solid state. Gas is hardly soluble in water and insoluble in liquid oxygen, but soluble in liquid nitrogen and lye. Liquid ozone decomposes slowly at normal temperature and rapidly decomposes at high temperature, producing oxygen, which can explode when impacted or rubbed. ^[3]

The decomposition rate of ozone in aqueous solution is faster than its decomposition rate in gas phase. The half-life of ozone decomposition in water is related to temperature and pH. As the temperature increases, the rate of decomposition increases. When the temperature exceeds 100 , the decomposition is severe; when the temperature reaches 270 , it can be converted into oxygen immediately. The higher the pH, the faster the decomposition. Decomposed in air at normal temperature and normal pressure, the half-life is about 15-30 minutes. ^[4]

The olfactory threshold of ozone is 0.02 mL / m ^3. If the concentration reaches 0.1 mL / m ³ , it will stimulate the mucous membranes. When the concentration reaches 2 mL / m ³ , it will cause central nervous system disorders. ^[3]

Strong ozone

Ozone can discolor most organic pigments. It can slowly attack rubber and cork, and oxidize organic unsaturated compounds. Commonly used in: disinfection and sterilization of beverages, air purification, bleaching, water treatment and disinfection of drinking water, granary killing mold and insect eggs; reaction with organic unsaturated substances can generate odor oxides, which can be decomposed in the presence of water , The original unsaturated bond opens the chain to form aldehydes, ketones and carboxylic acids. Due to ozone decomposition, it can be used as a synthetic means and to determine the structure of organic matter. ^[3]

Ozone has extremely strong oxidizing and bactericidal properties. It is one of the strongest oxidants in nature, and its redox potential is second only to fluorine in water. At the same time, the product of the ozone reaction is oxygen, so ozone is an efficient oxidant without secondary pollution. As a strong oxidant, its characteristics are as follows ^[5] : can be used as selective oxidation, high yield of the main product; low oxidation temperature, strong oxidation ability under normal pressure, and beneficial to the oxidation of sensitive substances; reaction speed Fast, quantitative oxidation; easy to use and manufacture. ^[5]

The application basis of ozone is its strong oxidizing and sterilizing capabilities. The application of ozone is classified according to its role, and can be divided into: sterilization, decolorization, deodorization, deodorization and oxidative decomposition. According to its application field, it is mainly used in the following fields: water treatment; food processing, storage, fresh-keeping; household appliances; medical and health; chemical oxidation. ^[5]

Ozone detection means

Ozone analysis methods include spectral analysis and electrochemical analysis. The commonly used detection methods are iodometric method, sodium indigo disulfonate spectrophotometric method, ultraviolet absorption method and chemiluminescence method. The iodometric method is commonly used in the laboratory. Passing ozone into potassium iodide solution can release iodine. This reaction can be used for the quantitative analysis of ozone. ^[3]

The iodometric method uses ozone and KI to generate I _2. Starch is used as an indicator, titrated with sodium thiosulfate, and it can also be colorimetrically determined at 550 nm after color development with starch reagents. ^[4]

A brief history of ozone development

As early as 1785, German physicist von Marum experimented with high-power motors and found that when a stream of sparks flows through the air, a special odor is produced, but it has not been studied. Later, in 1840, Shubein also discovered a unique odor during the electrolysis and electric spark discharge experiments, and concluded that it was generated by a new gas, thereby announcing the discovery of ozone. ^[6]

During World War I, some German soldiers first applied ozone to treat skin gangrene caused by anaerobic infections; in 1936, French doctor P. Aubourg 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 has been used clinically for more than 50 years in foreign countries, especially in Europe. After the 1990s, ozone application entered China. Ozone was mainly used in the treatment of lumbar disc herniation, scavenging free radicals and anti-aging. The clinical application is developing rapidly and is becoming a new drug and method with wide application and powerful effect. ^[7]

Since the early 1980s, China has begun to use ozone to pay attention to drinking water disinfection and industrial wastewater advanced treatment, but its development has been slow. In China's current urban water supply, most water plants use coagulation, sedimentation, filtration, and disinfection processes. The disinfection process mainly uses chlorine and bleach powder, and the use of ozone is very low. At the same time, the practice of applying ozone to cooling water treatment has just begun. However, due to a series of advantages such as economics, reliability, absolute non-toxicity, and no secondary pollution of ozone treatment, it can be predicted that ozone will also be popularized in our country. ^[5]

Ozone production method

The methods for generating ozone are mainly ultraviolet irradiation method, electrolytic method, radiochemical method and dielectric barrier discharge method.

Ozone UV irradiation

The ultraviolet irradiation method uses ultraviolet rays to irradiate dry oxygen, so that a part of oxygen molecules are activated to dissociate into oxygen atoms, thereby forming ozone. The disadvantages of UV irradiation to produce ozone are high energy consumption and low ozone concentration. Therefore, UV irradiation is not practical for mass production of ozone. It is only suitable for various tests with small and low concentrations, such as air disinfection, sterilization, Deodorization, etc., ^{[5] are} commonly used on disinfection cupboards.

Ozone electrolysis

The technology for preparing ozone by electrolytic method was established in 1840. It mainly uses low-voltage direct current to electrolyze water, so that water undergoes oxidation reaction at the anode-solution interface to generate ozone. The ozone preparation device is composed of an electrolyte solution and a yin-yang pole. Ozone is precipitated at the anode, and the cathode can be divided into two types, namely, a hydrogen evolution cathode and an oxygen reduction cathode. ^[8] Prior to the 1980s, most electrolytes were added acid and salt electrolytes in water. The electrolytic area was relatively small, the ozone production was low, and the operating costs were high. After a lot of research on electrode material, electrolyte and electrolysis mechanism and process, the technology of ozone production by electrolytic method has made great progress. Recently developed SPE (Solid Polymer Electrolyte) electrode and metal oxidation catalytic technology, electrolyzed purified water can obtain high concentration of more than 14% ozone. The ozone produced by electrolytic method has high concentration, pure composition, high solubility in water ^[5] , no pre-treatment of feed air is needed and no nitrogen oxides are produced; in addition, the ozone production equipment is small and light, simple in structure, and no noise And portable, so its application prospect is very broad. ^[8] The main disadvantage is the large energy consumption. After further improvements, trying to reduce costs and power consumption, it may compete with the widely used dielectric barrier discharge method. ^[5]

Among the methods for preparing ozone by electrolytic method, in which the method using lead dioxide as an electrode occupies the mainstream, how to improve the efficiency of ozone generation is the main research direction of generating ozone by electrolytic method. We know that in electrochemical reactions, pH, temperature, current density, and electrode type are the most critical. There are many reports on the modification of lead dioxide electrodes, such as adding a small amount of titanium dioxide to lead dioxide electrodes. Can greatly improve the current efficiency and conductivity of the lead dioxide electrode, but has not changed the corrosion problem of lead dioxide; and -type lead dioxide has better stability, and the price is moderate, and the ozone concentration can reach 13 % Or more, without generating harmful nitrogen oxides. However, -type lead dioxide is easy to recrystallize under high voltage and acidic conditions, which results in unstable catalytic efficiency of the anode catalytic layer. -type lead dioxide is easily desorbed, which makes the working life of the membrane electrode very short. It can also cause short circuit; the existing preparation process of the membrane electrode catalytic layer is not stable enough, and the main cause of this problem is that the catalytic layer is not very tightly attached to the membrane. Based on the advantages and disadvantages of lead dioxide and SPE membrane electrodes, follow-up research on lead dioxide and SPE composite membrane electrodes is necessary. ^[8]

Ozone Radiochemistry

Radiochemical method uses various sources of nuclear radiation to dissociate oxygen molecules to generate ozone. There are two processes in this method for industrial ozone production. One is the contact of oxygen with the fission product, and the ozone is generated by the thermal collision of radiation, oxygen with the fission product and secondary radiation. The second is to generate ozone only under radiation. This method uses radioactive sources because of its high cost and poor safety. It is only suitable for some special cases and not suitable for industrial mass production. ^[5]

Ozone Dielectric Barrier Discharge

Also called silent discharge method (abbreviated as DBD method). A corona is generated in the gas by an alternating high-voltage electric field. The free high-energy electrons in the corona dissociate oxygen molecules and polymerize into ozone molecules by collision. The dielectric barrier discharge method has the advantages of relatively low energy consumption, large single-unit ozone production, and dry air, oxygen, or oxygen-rich gas with a high oxygen concentration, and so on. Therefore, this method is mostly used in industrial ozone synthesis. ^[5]

In the last century, people usually produced ozone by thermochemical methods. Although the theoretical value of the ozone rate (energy generation efficiency of ozone generation) calculated by thermochemical theory is 1200 g / (kW · h), the conversion ratio in actual production is only 4% to 12%. The remaining energy is converted into heat dissipation, and the actual yield is far below the theoretical value. Since the 21st century, in order to increase the ozone concentration and yield in sealed containers and reduce production costs, scientists have conducted numerous academic discussions and exchanges. ^[9] With the continuous theoretical research and continuous improvement of technological processes, the main research directions focus on different raw materials, related gases, different electrode forms, different reaction media, electrode materials, and discharge forms. ^[9]

The basic principle of generating ozone during the plasma discharge is that in the low-temperature plasma atmosphere formed by the oxygen-containing gas in the discharge reactor, free electrons of a certain energy decompose oxygen molecules into oxygen atoms, and then ozone molecules are formed through a three-body collision reaction. At the same time, the decomposition reaction of ozone also occurs. ^[9]

Ozone ozone disinfection technology and application

Ozone ozone disinfection advantages

(1) No dead corner for disinfection, high sterilization efficiency, and deodorization. During the disinfection, the ozone generator generates a certain amount of ozone. In a relatively closed environment, the ozone is evenly diffused and has good permeability. It overcomes the problem of sterilization dead angle existing in ultraviolet sterilization and achieves the purpose of comprehensive, rapid and efficient sterilization. In addition, because of its broad sterilization spectrum, it can kill many kinds of microorganisms such as bacterial propagules, spores, viruses, fungi and protozoan spores, and can also destroy botulinum and toxins and rickettsials. It also has Strong odor removal function such as mildew, fishy, odor. ^[2]

(2) No residue or pollution. Ozone is produced by oxygen in the air. During the disinfection and oxidation process, excess oxygen atoms are combined into molecular oxygen after 30 minutes. There is no residual substance, which solves the problem of secondary pollution remaining during disinfection and eliminates Clean again after disinfection. ^[2]

Mechanism of ozone disinfection

Ozone is a strong oxidant. Its molecule is extremely unstable and can decompose to produce monoatomic oxygen (O) and hydroxyl (OH) with strong oxidation ability. It is a unique bactericidal preparation, which can quickly integrate into the cell wall, destroy bacteria, The internal structure of viruses and other microorganisms has a strong killing effect on various pathogenic microorganisms. The sterilization process is a biochemical oxidation reaction. Its role is mainly achieved by the following three forms: (1) ozone can oxidize and break down the enzymes needed for the internal glucose of bacteria to inactivate the bacteria; (2) it acts on nuclear materials in bacterial cells, such as purines in nucleic acids And pyrimidine, destroying their organelles and DNA and RNA, damaging the metabolism of bacteria, leading to bacterial death; (3) ozone reacts with bacterial cell wall lipid double-strands, penetrates cell membrane tissues, invades cells, and acts on the outer membrane Lipoprotein and lipopolysaccharide inside cause bacteria to permeate and dissolve and die; ^[7] (4) Ozone acts on the 4 polypeptide chains of the capsid protein of the virus, and damages the RNA and destroys its formation. protein. After the bacteriophage is oxidized by ozone, its epidermis is broken into many fragments, and a lot of ribonucleic acid is released from it, which interferes with its adsorption to the host. ^[2]

The effects of ozone are mainly concentrated in five aspects: anti-inflammatory and anti-infection, pain relief, cholesterol oxidation, improving the body's immunity, and supplying oxygen to ischemic tissue. However, because the molecular structure of ozone is a special molecule composed of three oxygen atoms, although it has strong oxidizing properties, it is also very unstable. At room temperature and pressure, it will automatically reduce to oxygen after 20 minutes. Therefore, the ozone used in clinical practice is now produced, and it is usually made by ozone generator. The 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 electricity or chemical reactions to decompose part of the oxygen in the air and polymerize it into ozone. It is an allotropic form of oxygen. A process of body transformation. After being made into ozone, it can be dissolved in sterilized water, blood, body fluids, or directly act on tissues as required to achieve different therapeutic purposes. ^[7]

Clinical application of ozone

The clinical application of ozone has been from the initial treatment of colitis and skin gangrene to today's treatment of stroke, rheumatic diseases, joint diseases, disc herniation, anti-free radical anti-aging, acute and chronic hepatitis, prostatitis, pressure ulcers Caused by chronic wounds, vaginitis, etc., but in terms of treatment effect, operation technology, promotion and application are mainly reflected in the following aspects: ^[7]

Treatment of herniated disc

The most widely used clinically, the more mature technology is the treatment of cervical and lumbar disc herniation. Percutaneous laser vaporization decompression combined with ozone interventional treatment is currently used. Under local anesthesia, needle loop technology is used. During laser vaporization, the position of the needle tip is continuously adjusted until the ideal position. A laser fiber is inserted into the laser fiber. Later, a certain concentration (50ug / ml) of ozone was injected into the intervertebral disc and the intervertebral space with a syringe to achieve anti-inflammatory and analgesic effects. It is not easy to relapse after treatment with this method, and it has no side effects on patients. At present, it is a new technology successively adopted by various hospitals. ^[7]

Treatment of viral liver disease

Ozone is also effective in treating acute and chronic viral hepatitis. In patients with viral hepatitis, inflammatory reactions such as edema and degeneration occur in liver cells due to virus infestation. Ozone is a strong oxidant, which can rapidly denature viral RNA and stop the metabolism of bacteria. Therefore, it plays an anti-inflammatory role. ^[7]

Ozone is also used to treat viral hepatitis because it also enhances human immunity and induces the production of cytokines to protect the liver. Research data also show that ozone treatment can quickly reduce transaminase in patients, reduce yellowing, reduce virus levels in the body, and inhibit virus replication. It is a new treatment with no toxic side effects. In 2000, ozone treatment for viral hepatitis was approved for clinical use in Europe. In 2004, this technology was approved for clinical treatment in China. ^[7]

Treatment of ischemic hypoxia

Tylicki et al. Reported that twelve hemodialysis patients with arteriosclerosis complicated by arterial thrombosis of the lower extremity underwent 9 high-pressure ozone large autohemotherapy treatments. As a result, total cholesterol decreased by an average of 8.34%, and low-density lipoprotein decreased by an average of 17.9%. There is no significant change in factor activity, which indicates that this method does not harm the patient's vascular endothelial system, and the reduction of total cholesterol and low density lipoprotein is beneficial to the improvement of lower limb arteriosclerosis. ^[7]

In China, ozone has been used to treat gynecological infections, such as candida vaginitis; there are also ozone water rinse combined with microwave treatment for chronic cervicitis, and ozone autohemotherapy has been applied to patients with bronchial asthma, and has achieved good results and It has been reported that ozone has been used to treat wound healing caused by burns. ^[7]

Since ozone has been used clinically 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), whose main purpose is to promote basic research and clinical application of ozone, and to provide normative standards for clinical treatment. ^[7]

At present, the association is working with a large number of medical workers to find new methods and directions for the application of ozone in the clinic. For example, when treating lumbar disc herniation, consider a multi-channel puncture approach, the combination of ozone technology and collagenase technology, Double needle technology and more. It is believed that there will be more and better new ozone technologies applied to the clinic soon, bringing the gospel to more and more patients. From this perspective, the development prospects of ozone should be very broad. However, there are contraindications to the use of ozone in clinical applications. ^[7]

First, ozone cannot be directly absorbed into the lung, because direct inhalation can cause alveolar epithelial cells to be destroyed; second, patients with broad bean disease cannot undergo ozone blood therapy; third, ozone treatment can cause very few allergic reactions; fourth, ongoing Excessive concentrations and doses can cause toxic reactions during ozone treatment. ^[7]

Ozone Vegetable Disease Control

The use of ozone to control vegetable diseases has long been studied abroad, and there have been related reports in China in recent years. The use of low-mass ozone produced by the ozone plant controller for greenhouse plant diseases can prevent all airborne diseases and most soil-borne diseases of fruit and vegetable crops such as cucumbers, green peppers, and eggplants in the greenhouse. Low mass fraction of ozone can effectively prevent large areas of cucumber downy mildew, powdery mildew, anthracnose, blight and mosaic virus, and it can also prevent eggplant and kidney bean gray mold. In addition to the significant control effect on diseases, ozone also has control effects on some pests, for example, the control rate of aphids reaches 63% to 68%. ^[10]

Ozone removes pesticide residues in vegetables

When eating vegetables, the most worrying issue is pesticide residues. Although the agricultural administrative department has formulated many measures to reduce the problem of pesticide residues, it emphasizes the rational use of pesticides, and promotes the use of biological pesticides and high-efficiency, low-toxicity, low-residue pesticides, but vegetable pesticide poisoning incidents often occur. The traditional methods for removing pesticide residues are: immersion and washing, immersion in alkaline water, peeling, storage, heating, etc. Dr. Pan Canping of China Agricultural University pointed out that traditional clear water soaking methods can hardly remove pesticide residues in vegetables and fruits, and high concentration ozone soaking can effectively remove pesticide residues. Studies have shown that when ozone is used to cultivate bean sprouts, ozone can effectively degrade pesticides on bean sprouts. The bean sprouts were soaked with 3mg / L of ozone water for 30 minutes and then cultured for 8 hours. The pesticide degradation on them was as follows: kebutan 100%, diazinon 76%, and dichlorvos 96%. Ozone was used to treat chlorothalonil, omethoate, trichlorfon, and dichlorvos on vegetables, and the pesticide residues after treatment all reached internationally acceptable standards. ^[10]

Ozone vegetable preservation processing

Washing and disinfecting vegetables

Utilizing the oxidation and bactericidal effects of ozone, washing fruits and vegetables with ozone-containing water can not only effectively kill pathogenic 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 foods. Studies have shown that this method can reduce the total number of bacteria on the surface of fruits and vegetables by more than 90%, especially the killing effect on Escherichia coli. ^[10]

Fresh cut vegetables

Western developed countries began to research and produce fresh-cut vegetables as early as the 1950s, and now they have formed a complete, advanced and systematic processing system. With the acceleration of people's life and the improvement of food safety awareness, fresh-cut vegetables are gradually popular in China. However, at present, most fresh-cut vegetables sold in general supermarkets undergo rough processing such as simple cleaning and slitting, and lack of advanced purification treatment processing techniques. Consumers still have concerns in their hearts, and they still have questions about its safety and hygiene. . Ozone has a good killing effect on the microorganisms on the surface of vegetables, and its oxidizing property can oxidize and damage the 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, some researches on the application of ozone in fresh-cut vegetables have been carried out at home and abroad. Studies show that immersion in ozone water can not only significantly reduce the microorganisms on the surface of fresh-cut vegetables, improve the safety of the product in terms of microorganisms, but also significantly inhibit The degradation of chlorophyll in fresh-cut vegetables inhibits the activity of polyphenol oxidase and protects vitamin C, but may have a certain oxidative effect on reducing sugars. ^[10]

Vegetable storage

After harvesting vegetables, they are still living organisms. Respiration is one of the most important physiological activities after harvesting vegetables. Inhibition of respiration can extend the shelf life of vegetables. Numerous experiments have shown that ozone can significantly inhibit its respiration in the storage of vegetables. The principle is that vegetables easily release ethylene during storage, and ozone can oxidize and remove ethylene, thereby slowing the metabolism of fruits and vegetables. In addition, ozone can also destroy the foul odor of organic or inorganic substances, and has the functions of deodorizing and purifying the air. Therefore, it can be used for disinfecting the vegetable storage environment and maintaining an environment that is conducive to maintaining the vitality of vegetables. ^[10]

Desalted salted vegetables

Vegetables are prone to eat in high season and not enough in low season. People usually make some kimchi and salted vegetables. For example, mustard, snow cabbage, radish, etc. are the main pickled vegetables. When pickling, 8% to 15%, or even higher concentrations of salt are used for pickling. The taste is too salty to be eaten directly, and may even appear. Salt poisoning. Therefore, salted vegetables need to be eaten after desalting. The traditional desalination method uses tap water to soak. After desalting, microorganisms multiply in large numbers, especially in summer, which are prone to long film, raw flowers, and softness. Ozone has the characteristics of killing a variety of microorganisms. Some studies have shown that the number of microorganisms in salted vegetables desalted by ozone soaking is significantly lower than that of salted vegetables soaked in tap water. ^[10]

Ozone ozone oxidation technology and application

Ozone oxidation mechanism

Ozone has a strong oxidizing property because the oxygen atom in the ozone molecule has a strong electrophilic or protonic property. After ozone decomposition, new ecological oxygen atoms are generated, and a strong oxidizing group-hydroxyl radical can be formed in water, which can quickly remove organic pollutants in waste water, and decompose itself into oxygen without causing secondary pollution. ^[4]

At present, there are two ways in which ozone reacts with organic substances:

(1) Ozone reacts directly with organic matter in water as oxygen molecules. ^[4]

This method is more selective and generally attacks organics with double bonds, and has better effect on aromatic hydrocarbons and unsaturated aliphatic hydrocarbon organic compounds. ^[4]

(2) Under alkaline conditions, ozone decomposes in water to produce highly oxidizing intermediates such as hydroxyl radicals. The hydroxyl radicals undergo oxidation reactions with organic compounds. ^[4]

This oxidation method is non-selective. ^[4]

Ozone wastewater treatment

Ozone oxidation technology is used in wastewater treatment in the following two cases: (1) Ozone is used as pre-treatment or post-treatment in combination with other methods, such as flocculation + ozone, ozone + biological filter (biological activated carbon method, etc.), and ozone + membrane Treatment; (2) ozone self-oxidation treatment, such as: ozone, ozone-hydrogen peroxide, ozone-hydrogen peroxide / UV photooxidation, ozone / UV photooxidation, ozone-solid catalyst (solid catalyst such as activated carbon, etc.). ^[4]

Coagulation-Ozone Oxidation Technology

Coagulation-ozone oxidation technology is the treatment of wastewater using ozonation technology under the condition of adding coagulant. Ozone can change the nature of suspended solids in water, thereby changing the removal effect of the coagulation operation unit. This method can increase the size of suspended particles in water, so that dissolved organic matter can be mixed into gel particles, thereby reducing the dosage of coagulant. Volume, reducing chemical consumption. ^[4]

Ozone-Biochemical

The use of ozone-catalyzed oxidation combined with biological activated carbon filters to treat wastewater has been reported in recent years. It is collectively referred to as the use of ozone to pretreat wastewater to destroy difficult-to-degrade organic matter in the water, improve biodegradability, and then use activated carbon biological filters for further processing. This technology makes full use of the strong oxidizing properties of ozone and also takes advantage of the cost advantage of biological filters. The combined post-treatment effect is good. ^[4]

Ozone-membrane treatment technology

A patent has disclosed an ozone-catalyzed oxidation-ceramic membrane filtration advanced treatment of coking wastewater. A combination of ozone-catalyzed oxidation and ceramic membrane separation has been used to implement the application of powder catalysts in dynamic reactors. ^[4]

The reaction system ensures segmented ozone oxidation and catalytic ozone oxidation in a single reactor, reduces the mass transfer resistance during separate ozone oxidation and catalytic ozone oxidation, improves the utilization rate of hydroxyl radicals and the removal rate of organic substances, and finally achieves coking The COD, chromaticity and turbidity of the effluent from the advanced treatment of wastewater reached the standards. ^[4]

Ozone direct aeration treatment

A two-stage ozone catalytic oxidation treatment method is adopted for the secondary biochemical effluent, that is, the bottom of the first-stage ozone catalytic oxidation pond is connected to the second-stage ozone catalytic oxidation pond, and the second-stage ozone catalytic oxidation pond is provided with a total water outlet to realize energy saving and cost reduction. Can improve COD removal rate by 20%. ^[4]

A patent has disclosed an ozone treatment system that reduces the COD concentration in organic amine wastewater, and uses ozone oxidation to reduce the COD of organic amine wastewater. The system divides the ozone reaction tank into three front, middle and rear contact oxidation reaction tanks, which are divided by partitions, and the three contact oxidation tanks are successively reduced in volume. This method is used to perform oxidation treatment in contact with oxidizing place to realize the treatment of organic amine-containing wastewater and reach the discharge standard. ^[4]

Ozone-hydrogen peroxide combined oxidation

Ozone-hydrogen peroxide system is an advanced oxidation method for wastewater treatment. The synergistic effect of ozone and hydrogen peroxide can generate hydroxyl radicals with strong oxidation, which can effectively remove organic pollutants in water. The mechanism shows that the addition of hydrogen peroxide promotes the generation of hydroxyl radicals, and the effect of pH is also obvious. The concentration of hydrogen peroxide anion is a key factor affecting the generation of hydroxyl radicals, and the pH value also has a large effect on the concentration of hydrogen peroxide anion, so pH is an important condition that affects the reaction; at the same time, the ozone-peroxide ratio also affects organic pollutants A key factor in removing results. In addition, the ozone-hydrogen peroxide process is also effective for removing organic pollutants from natural water bodies. ^[4]

Ozone-Hydrogen Peroxide-UV Photooxidation

Oxidation combined with catalytic oxidation technology UV light oxidation-ozone method is an advanced oxidation process combining ozone with ultraviolet light radiation, which began in 1970. The ozone-hydrogen peroxide-UV photo-oxidation method is more effective in treating difficult-to-oxidize substances, and can increase the oxidation rate by 10 to 10,000 times. ^[4]

The oxidation reaction in the UV photo-oxidation-ozone method is a free radical type, that is, liquid-phase ozone is decomposed under ultraviolet light radiation to generate an · OH radical, and the · OH radical reacts with a dissolved substance in water. ^[4]

Ozone-solid catalyst technology

Ozone-Solid Catalyst Technology Solid catalysts include activated carbon, metals and their oxides. The ozone / activated carbon combined system can significantly improve the removal rate of COD and TOC, and shows a good synergistic effect, which can improve the biodegradability of refractory pharmaceutical organic wastewater. The removal rate of acetophenone by activated carbon adsorption-catalytic ozone oxidation technology increases with the increase of the amount of ozone gas intake and the amount of activated carbon added. Under the optimal process conditions, the removal rate of acetophenone can reach 92.3%. ^[4]

Ozone oxidation treatment of wastewater, whether it is an ozone-ultraviolet combination or ozone-hydrogen peroxide synergistic catalytic oxidation technology, is essentially a hydroxyl radical oxidation degradation of various pollutants in wastewater, does not form secondary pollution, and has a broad application prospect in wastewater treatment .

At present, the main problem affecting the application of advanced ozone oxidation technology is the low utilization rate of ozone. ^[4] The research and application of ozone in various fields of wastewater treatment are increasing. Ozone technology has the characteristics of strong oxidation in the treatment of wastewater, cheap and easy preparation of raw materials, can handle a variety of pollutants, and no secondary pollution occurs after the reaction. Although ozone can oxidize many difficult-to-degrade organics in water, it is not easy to completely decompose organics into CO ₂ and H ₂ O. Its products are often carboxylic acids that are easily biodegradable organics, such as: monoaldehyde, dialdehyde, uronic acid, and monocarboxylic acid. Acids and dicarboxylic acids are small organic molecules. Therefore, in most cases, ozone is more suitable for use with other purification technologies to achieve the ultimate wastewater treatment goal. ^[11]

Ozone flue gas purification

Ozone has broad prospects in the field of flue gas purification: (1) ozone is a clean oxidant and does not produce secondary pollutants; (2) it can achieve high efficiency of mercury on the basis of good desulfurization and denitration Removal; (3) Ozone also has a certain ability to remove chlorides, fluorides, VOCS and dioxins in the flue gas. Its ability to remove multiple pollutants synergistically is the most advantageous advantage in practical applications. ^[12] Although the ozone method is an efficient pollution control method in the field of flue gas purification, the cost of ozone preparation is high at this stage, and the application technology is not mature enough, which limits the widespread promotion of this technology. Therefore, the ozone is highly efficient, energy-saving and environmentally friendly The generator is still the key to the application of the ozone method. ^[12]

Ozone hazard

Ozone tropospheric ozone pollution

About 90% of global ozone is concentrated in the stratosphere, and another 10% is in the troposphere. Ozone is the most critical component of the natural atmosphere in the stratosphere. The peak of ozone concentration occurs at a distance of 10 to 25 km from the ground. The ozone in the stratosphere can absorb short-wave ultraviolet radiation, reduce damage to humans, animals and plants, and is a protective umbrella for the living matter of the earth. The presence of tropospheric ozone not only affects the oxidative properties of the atmosphere, but also due to the strong oxidative properties of ozone, it can participate in the chemical conversion process of a variety of atmospheric pollutants and cause harm to humans, ecosystems, and urban construction. ^[13]

Ozone is harmful to the human body

According to the National Ambient Air Quality Standards (NAAQS), the limiting concentration of ozone that humans can accept within one hour is 260 g / m ³ . Coughing, dyspnea, and decreased lung function can be caused by activity in an ozone environment of 320 g / m ³ for 1 hour. Ozone can also participate in the reaction of unsaturated fatty acids, amino groups and other proteins in the organism, which makes people who have been in direct contact with high concentrations of ozone for a long time appear fatigue, cough, chest tightness, chest pain, skin wrinkling, nausea and headache, pulse acceleration, memory loss, vision Drop and other symptoms. ^[13]

Other hazards of ozone

Ozone will also make plant leaves yellow or even wither, causing damage to plants, and even reducing the yield and economic benefits of agricultural and forestry plants. Ozone can quickly react with indoor building materials (such as surface coatings such as latex coatings), household products (such as cork appliances, carpets, etc.), silk, cotton, cellulose acetate, nylon and polyester. Saturated carbon-carbon bond organic compounds (including rubber, styrene, unsaturated fatty acids and their esters) react, causing dye fading, discoloration of photo and image layers, and aging of tires. ^[13]

Ozone ozone pollution control

Ozone ozone pollution source

The sources of ozone are divided into natural and man-made sources. Ozone from natural sources mainly refers to the transmission of the stratosphere. In 1962, Junge research believed that under the radiation condition of ultraviolet light with a wavelength less than 240nm, the ozone in the stratosphere will decompose, and the generated oxygen atoms and oxygen molecules will combine to generate ozone. source. ^[13]

Anthropogenic ozone is mainly produced by the photochemical reaction of anthropogenic emissions of NOx, VOCs and other pollutants. Under sunny conditions and strong ultraviolet radiation, NO ₂ etc. undergo photolysis to generate nitric oxide and triplet oxygen atoms, and triplet oxygen atoms react with oxygen to generate ozone. Ozone is a strong oxidant. In a clean atmosphere, ozone reacts with nitric oxide to form NO ₂ , and ozone decomposes into oxygen. The existence of the above reaction allows ozone to reach an equilibrium state in the atmosphere without causing ozone accumulation. When there are a large number of pollutants such as VOCs in the air, the free radicals generated by VOCs and the like react with nitrogen monoxide to form nitrogen dioxide. This reaction competes with the reaction of ozone and nitric oxide and continuously replaces the consumption of nitrogen dioxide. NO. The peroxy radicals HO ₂ , RO ₂ , H, and OH caused the conversion of NO to NO ₂ , which disrupted the above-mentioned dynamic equilibrium, resulting in the gradual accumulation of ozone and reaching the difficulty level of pollution ^[14] . Ozone precursors such as NOx, VOCs, and CO are all primary pollutants. They mainly come from exhaust emissions from vehicles, industrial pollution sources such as petrochemicals and thermal power generation, and pollution sources from the food, printing, and real estate industries. A large amount of biomass such as straw will also produce a large amount of VOCs and ozone precursors such as NOx. ^[13]

Ozone ozone pollution monitoring

The "Ambient Air Quality Standard" (GB3095-2012) issued in February 2012 in China stipulates that the daily maximum 8-hour average secondary concentration limit of ozone is 160 g / m ³ . As one of the six major pollutants in the air, ozone pollution monitoring is one of the important contents of ozone pollution prediction and prevention. The successful development of the Dobson spectrophotometer in 1929 laid the foundation for ground-level observations of atmospheric ozone. China began to observe the total ozone content in the 1950s, and successively established the Xianghe Ozone Observation Station and the Kunming Ozone Observation Station. The instruments used were Dobson ozone spectrophotometers. There are more than ten methods for measuring ozone, such as test paper colorimetry, differential spectroscopy, coulomb, polarography, gas chromatography, chemiluminescence and fluorescence. ^[13]

The current standard methods for the determination of ozone in China mainly include two methods: "Ambient Air Ozone Determining Sodium Indigo Disulfonate Spectrophotometric Method" (HJ 504-2009) and "Ambient Air Ozone Determining Ultraviolet Photometric Method" (HJ 590-2010). Analytical methods, automatic monitoring methods mainly include ultraviolet fluorescence method and differential absorption spectrum analysis method. ^[13]

At the end of the Twelfth Five-Year Plan period, China has established a national environmental air quality monitoring network. The national ambient air quality monitoring network consists of urban stations, regional stations, and background stations. The monitoring content includes real-time hourly concentration values and daily average concentrations of six monitoring indicators including SO ₂ , NO ₂ , PM10, PM2.5, O ₃ and CO. Value, you can grasp the ozone index data of monitoring points in real time, find out the pollution characteristics of key areas, and improve air quality forecast and early warning capabilities. Technical Requirements and Detection Methods for Continuous Automatic Monitoring System of Gaseous Pollutants in Ambient Air, published on July 30, 2013 (HJ 654-2013), which stipulates the composition, technical requirements and performance indicators of continuous automatic monitoring systems for gaseous pollutants in ambient air And detection methods. Later, the Regulations on the Management of the Transmission of Automatic Monitoring Standards for Ambient Air (Trial) (Environment Office Monitoring Letter [2017] No. 242) and the Implementation Rules for the Operation and Management of Urban Stations of the National Ambient Air Quality Monitoring Network (Environment Office Monitoring Letter [2017] ] No. 290). On October 17, 2017, the Ministry of Environmental Protection also issued the Guideline for Ambient Air Ozone Level One Calibration Operation (Trial), Guideline for Ambient Air Ozone Standard Reference Photometer Indirect Comparison Operation (Trial), and Ambient Air Ozone Transfer Standards Interim step-by-step calibration operation guide (trial) "Ambient air ozone automatic monitoring field comparison and verification operation guide (trial)" 4 work instructions related to ozone monitoring, which has improved the national ozone monitoring quality control system and will Ozone is regularly monitored and inspected under a uniform standard. ^[13]

On February 22, 2018, in order to implement the "Monitoring Plan for Volatile Organic Compounds in Environmental Air in Key Areas in 2018", the Ministry of Ecology and Environment issued the "Technical Requirements for Manual Monitoring of Ozone Precursor Organic Compounds in Ambient Air (Trial)" (Environmental Office Monitoring Letter [ 2018] No. 240) to further standardize manual monitoring of ambient air ozone precursor organic matter. ^[13]

Ozone Ozone Forecast

As early as the 1970s, the European Medium-Term Weather Forecasting Platform (ECMWF) was established. In 1979, for the first time, Europe successfully released a medium-term numerical forecast. At the end of the 20th century, the Institute of Atmospheric Physics of the Chinese Academy of Sciences established a "Numerical Air Quality Numerical Simulation System" and carried out numerical predictions of air pollutants in Tianjin, Shenyang and other cities. On December 16, 2007, the Shanghai Meteorological Observatory released daily ozone forecasts for the first time. At that time, in order to assess the impact of the atmospheric environment on ecology and human health, similar forecasts have been developed in Europe and the United States, among which ozone forecasting is one of the main products of weather forecasting. ^[13]

With the increasing degree of ozone pollution and the deepening of people's understanding of the dangers of ozone, accurate prediction of ozone is particularly important. Provinces such as Shanghai and Guangdong have been conducting ozone forecasting for many years. On January 16, 2018, the person in charge of the China Meteorological Administration stated that the national ozone weather forecast will be carried out in 2018 to provide support for the ecological environment department. ^[13]

Ozone control measures

China's control of ozone pollution is still in its infancy. Ozone pollution is different from smog. Its generation mechanism is complex and it is difficult to control. At the public level, we must not only pay attention to personal health protection, but also actively participate in ozone prevention and control. When ozone is contaminated, wearing a mask can hardly block the inhalation of ozone. Therefore, when ozone pollution is serious, children and the elderly should try to avoid going out when the sun is strong in the afternoon, stay away from the roadside, and the place with serious pollution pollution. At the national level, it is currently necessary to establish a coordinated control mechanism for ozone and PM2.5, and to develop effective ozone pollution control measures. ^[13]

Volatile organic compound pollutants and nitrogen oxides are important precursors for the formation of ozone. To control ozone pollution, we must coordinately control the emissions of volatile organic compounds and nitrogen oxides. Such as: using natural gas, solar energy, wind energy, biomass energy and other clean energy sources, rectifying all kinds of scattered pollution enterprises, limiting the total consumption of coal, etc .; optimizing development methods, improving process design, in thermal power, steel, cement building materials, coking, nonferrous metals Key industries such as oil refining, chemicals, pesticides, packaging, printing, etc. implement clean production to reduce pollutant emissions; control the number of urban vehicles, further tighten exhaust emission standards, encourage the purchase and use of clean energy vehicles, and reduce motor vehicle exhaust emissions . According to the "Air Pollution Prevention and Control Action Plan", by adopting comprehensive prevention and control measures, adhere to the combination of government regulation and market regulation, comprehensive advancement and key breakthroughs, regional coordination and territorial management coordination, total emissions reduction and quality improvement, A new air pollution prevention mechanism under government control, corporate governance, market drive, and public participation was formed. ^[13]