ozone
發(fā)布時間:2020-08-18 08:25:45人氣：次
Introduction to ozone
1. What is ozone
Ozone is a molecule (O3) formed by the combination of three atoms of oxygen (o). Ozone is also known as superoxide or hyperoxia, molecular symbol O3, English name ozone. When its concentration is high, it is light blue. The earliest time is 1785. After thunderstorm, van Marum of Germany found that the air was particularly fresh. Because of its unique grass flavor, ozone was known to exist. In 1840, schorbein was named "ozone". "Ozone"
2. Physical properties of ozone:
The ozone density ρ = 2.144g/i, air density = 1.293 g / I. The molecular weight of ozone is 48 and that of air is 29. So ozone is heavier than air. The solubility of ozone in water is about 10-15 times of that of oxygen, and its stability in water and air is relatively poor. Ozone is easy to decompose. The half-life of ozone is 30 minutes at room temperature, and the decay rate of one hour is 61%. In 1% ozone aqueous solution, the half-life is 16 minutes. The higher the temperature, the higher the humidity, the shorter the half-life. Therefore, ozone is not easy to store and needs to be used while producing
3. Chemical properties of ozone:
When ozone is produced, the third atomic oxygen in the molecular structure of ozone will continue to dissociate or escape from this structure. When it is released, it will produce great oxidation effects such as sterilization, detoxification, bleaching and deodorization in an instant. If ozone does not react with other substances, it will decompose into pure oxygen (O2). Ozone is more active than oxygen (O2), its oxidation capacity is only inferior to that of fluorine, and its bactericidal power is 3000 times that of chlorine. Ozone can eliminate the planktonic bacteria in the air and water in time, neutralize and decompose all kinds of toxic substances, remove all malodor, and bleach and clarify the pollutants in water
3.1 sterilization
Ozone is a very strong gas oxidant, bactericide and disinfectant. It can effectively make microbial cells produce a variety of oxidation reactions from outside to inside, directly destroy its RNA or DNA substances, and completely kill bacteria and mold microorganisms. Ozone first acts on the cell membrane, which damages the components of the membrane, resulting in metabolic disorders and inhibiting its growth. Ozone penetrates into the membrane and destroys its structure. Because of the expansion and thinning of cell membrane under high humidity, the tissue is easy to be destroyed by ozone. It can be used in air, water and object surface.
3.2 reaction with inorganic substances
Except platinum, gold, iridium and fluorine, ozone can oxidize almost all the elemental reactions in the periodic table. Ozone can react with K and Na to form oxides or peroxides, in which the anion O3 is essentially a free radical. Ozone can oxidize transition metal elements to higher or highest oxidation state and form more insoluble oxides. People often use this property to remove Fe2 +, Mn2 + and heavy metal ions such as Pb, Ag, CD, Hg and Ni from wastewater. In addition, ozone is also a combustion supporting agent. The combustion of combustibles in ozone is more violent than that in oxygen, and higher temperature can be obtained. It can be applied to decolorization, deodorization and removal of heavy metals in water.
give an example:
A. Reaction of ozone with ferrous iron: 2Fe + O3 → Fe2O3
B. The reaction of ozone and sulfide: H2S + O3 → SO2 + H2O
3.3 reaction with organic matter
Ozone reacts with organic matter in three different ways: one is the ordinary chemical reaction; the other is the formation of peroxide; the third is the decomposition of ozone or the formation of ozone oxides. Such as harmful substances xylene and ozone reaction, the formation of non-toxic water and carbon dioxide. The so-called ozone decomposition refers to the reaction of ozone with polar organic compounds, which is the reaction at the original double bond position of organic compounds to split their molecules into two. The oxidation of ozone causes the breakdown of unsaturated organic molecules into two. Ozone molecules are bound to the double bond of organic molecules to form ozone oxides. The spontaneous division of ozonation produces a carboxyl compound and an amphoteric ion with acid and basic groups. The latter is unstable. Due to the strong oxidation power of ozone, it can not only kill bacteria, but also remove the color, smell and other organic matters in water. This is its advantage. However, its spontaneous decomposition and performance are unstable, so it can only be used as it is used, so it is not suitable for storage and transportation It's a drawback. Of course, from the point of view of water purification and air purification, because of its rapid decomposition and no residual substances, it can be said to be a great advantage of ozone. It can be used in decolorization, deodorization, fresh keeping and chemical experiments.
Example: Ozone Preservation, reaction with ethylene (C2H4): h2c-ch2 + 2O3 → 2co2 + 2H2O
4. Ozone safety
Ozone has strong oxidation, ozone is a strong oxidizing gas, is a non-toxic gas, the so-called toxic, in fact, after the human body inhaled a large number of ozone on the human respiratory tract serious damage caused by the "ozone accident.". The concentration that can be sensed by smell in the air is 0.02ppm. The maximum concentration allowed for workers to work in ozone environment for a long time (8 hours) is 0.15ppm. The concentration of ozone harmful to human body is ≥ 2ppm.
2、 Brief introduction of ozone generator
We are familiar with the natural conditions to produce ozone is thunder, because at that time, high pressure will be generated, oxygen O2 will be reduced to oxygen atom 0 under high pressure, and the combination of three oxygen atoms will form an ozone molecule O3. In fact, a certain amount of ozone gas will be generated around machines and equipment that can generate high pressure, such as printers and plastic film production equipment.
The artificial methods can be divided into chemical method, electrolysis method, ultraviolet irradiation method and silent discharge method. Among them, the silent discharge method is the most widely used and has the highest efficiency.
1. High voltage discharge ozone generator:
1.1 according to the high voltage electric frequency of the generator, there are three kinds: power frequency (50-60Hz), intermediate frequency (400-1000hz) and high frequency (> 1000Hz).
1.2 according to the gas raw materials used, there are oxygen type and air type. Oxygen type is usually supplied by oxygen cylinder or oxygen generator. Air type usually uses air (such as compressed air) as raw material. Because ozone is produced by oxygen, and the content of oxygen in the air is only 21%, so the concentration of ozone produced by air generator is relatively low, and nitrogen compounds can be derived at the same time. The oxygen purity of bottled or oxygen generator is more than 90%, so the ozone concentration of oxygen generator is higher. Air generator is usually used in air disinfection. In water treatment, priority should be given to oxygen generator.
1.3 according to the cooling mode, there are water cooling type and air cooling type. When the ozone generator works, it will produce a lot of heat energy, which needs to be cooled. Otherwise, ozone will decompose at the same time because of high temperature. The water-cooled generator has good cooling effect, stable operation, no attenuation of ozone, and can work continuously for a long time, but the structure is complex and the cost is slightly higher. The air-cooled cooling effect is not ideal, and the ozone attenuation is obvious. High performance ozone generators with stable overall performance are usually water-cooled. Air cooling is generally only used for low and medium grade ozone generators with small ozone production. When selecting the generator, the water-cooled type should be selected as far as possible.
1.4 according to the dielectric materials, the common types are quartz glass tube, ceramic plate, ceramic tube and enamel tube. Quartz tube is often used by some high performance ozone generators because of its high dielectric constant, uniform wall thickness, good ellipticity, high temperature resistance and humidity resistance. The ceramic plate is easy to crack, so it is only suitable for some small generators. It is difficult to control the wall thickness and ellipticity of ceramic tubes, which leads to the problem of uneven discharge. Enamel tube has low dielectric constant, poor high temperature resistance, easy to burst, and the cost is much higher than other types, only used in some large equipment.
1.5 according to the structure of ozone generating parts, there are two types: closed type and open type. The structure characteristic of the closed generator is that the sealing body itself is the electrode, and ozone can be used intensively, such as for water treatment. The electrode of the open generator is exposed in the air, and the ozone generated can not be used intensively. It is usually only used for air purification in small space or disinfection of some small objects. Closed generator can replace open generator. The cost of closed generator is much higher than that of open generator
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