OZONE (O 3) is an allotropic modification of oxygen, its molecule consists of three oxygen atoms and can exist in all three states of aggregation. The ozone molecule has an angular structure in the shape of an isosceles triangle with an apex of 127 o. However, a closed triangle is not formed, and the molecule has the structure of a chain of 3 oxygen atoms with a distance between them of 0.224 nm. According to this molecular structure, the dipole moment is 0.55 debye. The electronic structure of the ozone molecule contains 18 electrons, which form a mesomerically stable system that exists in various boundary states. The boundary ionic structures reflect the dipole nature of the ozone molecule and explain its specific reaction behavior in comparison with oxygen, which forms a radical with two unpaired electrons. The ozone molecule consists of three oxygen atoms. The chemical formula of this gas is O 3 The reaction of ozone formation: 3O 2 + 68 kcal/mol (285 kJ/mol) ⇄ 2O 3 The molecular weight of ozone is 48 At room temperature, ozone is a colorless gas with a characteristic odor. The smell of ozone is felt at a concentration of 10 -7 M. In the liquid state, ozone is a dark blue color with a melting point of -192.50 C. Solid ozone is black crystals with a boiling point of -111.9 C. At a temperature of 0 deg. and 1 atm. = 101.3 kPa ozone density is 2.143 g/l. In the gaseous state, ozone is diamagnetic and is pushed out of the magnetic field; in the liquid state, it is weakly paramagnetic, i.e. has its own magnetic field and is drawn into the magnetic field.
Chemical properties of ozone
The ozone molecule is unstable and, at sufficient concentrations in the air under normal conditions, spontaneously turns into diatomic oxygen with the release of heat. Increasing temperature and decreasing pressure increase the rate of ozone decomposition. Contact of ozone even with small amounts of organic substances, some metals or their oxides sharply accelerates the transformation. The chemical activity of ozone is very high; it is a powerful oxidizing agent. It oxidizes almost all metals (except gold, platinum and iridium) and many non-metals. The reaction product is mainly oxygen. Ozone dissolves in water better than oxygen, forming unstable solutions, and the rate of its decomposition in solution is 5-8 times higher than in the gas phase than in the gas phase (Razumovsky S.D., 1990). This is apparently not due to the specificity of the condensed phase, but to its reactions with impurities and hydroxyl ion, since the rate of decomposition is very sensitive to the content of impurities and pH. The solubility of ozone in sodium chloride solutions obeys Henry's law. With an increase in the concentration of NaCl in an aqueous solution, the solubility of ozone decreases (Tarunina V.N. et al., 1983). Ozone has a very high electron affinity (1.9 eV), which determines its properties as a strong oxidizing agent, surpassed only by fluorine (Razumovsky S.D., 1990).Biological properties of ozone and its effect on the human body
Its high oxidizing ability and the fact that many chemical reactions involving ozone produce free oxygen radicals make this gas extremely dangerous for humans. How ozone gas affects humans:- Irritates and damages respiratory tissue;
- Affects cholesterol in human blood, forming insoluble forms, which leads to atherosclerosis;
- Long-term exposure to an environment with high ozone concentrations can cause male infertility.
- Maximum single maximum permissible concentration (MPC m.r.) in the atmospheric air of populated areas 0.16 mg/m 3
- Average daily maximum permissible concentration (MPC s.s.) – 0.03 mg/m 3
- The maximum permissible concentration (MPC) in the air of the working area is 0.1 mg/m 3 (at the same time, the threshold of human smell is approximately equal to 0.01 mg/m 3).
Harmful and beneficial properties of ozone
Ozone is present in two layers of the atmosphere. Tropospheric or ground-level ozone, located closest to the Earth's surface layer of the atmosphere the troposphere is dangerous. It is harmful to humans and other living organisms. It has a detrimental effect on trees and crops. In addition, tropospheric ozone is one of the main “ingredients” of urban smog. At the same time, stratospheric ozone is very useful. The destruction of the ozone layer (ozone screen) formed by it leads to the fact that the flow of ultraviolet radiation onto the earth's surface increases. Because of this, the number of skin cancers (including the most dangerous type, melanoma), and cases of cataracts is increasing. Exposure to harsh ultraviolet radiation weakens the immune system. Excessive UV radiation can also be a problem in agriculture, as some crops are extremely sensitive to ultraviolet light. At the same time, it should be remembered that ozone is a poisonous gas, and at a level earth's surface it is a harmful pollutant. In summer, due to intense solar radiation and heat, a particularly large amount of harmful ozone is formed in the air.Interaction of ozone and oxygen with each other. Similarities and differences.
Ozone is an allotropic form of oxygen. Allotropy is the existence of the same chemical element in the form of two or more simple substances. IN in this case Both ozone (O3) and oxygen (O2) are formed by the chemical element O. Obtaining ozone from oxygen Typically, starting material To produce ozone, molecular oxygen (O 2) acts, and the process itself is described by the equation 3O 2 → 2O 3. This reaction is endothermic and easily reversible. To shift the equilibrium towards the target product (ozone), certain measures are used. One way to produce ozone is to use an arc discharge. The thermal dissociation of molecules increases sharply with increasing temperature. So, at T=3000K, the content of atomic oxygen is ~10%. Temperatures of several thousand degrees can be achieved using an arc discharge. However, at high temperatures, ozone decomposes faster than molecular oxygen. To prevent this, you can shift the equilibrium by first heating the gas and then suddenly cooling it. Ozone in this case is an intermediate product during the transition of the O 2 + O mixture to molecular oxygen. The maximum concentration of O 3 that can be obtained with this production method reaches 1%. This is sufficient for most industrial purposes. Oxidative properties of ozone Ozone is a powerful oxidizing agent, much more reactive than diatomic oxygen. Oxidizes almost all metals and many non-metals with the formation of oxygen: 2 Cu 2+ (aq) + 2 H 3 O + (aq) + O 3(g) → 2 Cu 3+ (aq) + 3 H 2 O (1) + O 2 (g) Ozone can participate in combustion reactions, the combustion temperature is higher than during combustion in an atmosphere of diatomic oxygen: 3 C 4 N 2 + 4 O 3 → 12 CO + 3 N 2 The standard potential of ozone is 2.07 V, therefore The ozone molecule is unstable and spontaneously turns into oxygen with the release of heat. At low concentrations, ozone decomposes slowly, at high concentrations it decomposes explosively, because its molecule has excess energy. Heating and contact of ozone with minute amounts of organic substances (hydroxides, peroxides, metals of variable valence, their oxides) sharply accelerates the transformation. On the contrary, the presence of small amounts of nitric acid stabilizes ozone, and in vessels made of glass and some plastics or pure metals, ozone practically decomposes at -78 0 C. The electron affinity of ozone is 2 eV. Only fluorine and its oxides have such a strong affinity. Ozone oxidizes all metals (except gold and platinum), as well as most other elements. Chlorine reacts with ozone to form hypochlorine OCL. Reactions of ozone with atomic hydrogen are the source of the formation of hydroxyl radicals. Ozone has an absorption maximum in the UV region at a wavelength of 253.7 nm with a molar extinction coefficient: E = 2.900 Based on this, the UV photometric determination of ozone concentration together with iodometric titration is accepted as international standards. Oxygen, unlike ozone, does not react with KI.Ozone solubility and stability in aqueous solutions
The rate of ozone decomposition in solution is 5-8 times higher than in the gas phase. The solubility of ozone in water is 10 times higher than that of oxygen. According to various authors, the solubility coefficient of ozone in water ranges from 0.49 to 0.64 ml ozone/ml water. Under ideal thermodynamic conditions, equilibrium obeys Henry's law, i.e. the concentration of a saturated gas solution is proportional to its partial pressure. C S = B × d × Pi where: C S is the concentration of a saturated solution in water; d—ozone mass; Pi—ozone partial pressure; B—dissolution coefficient; The fulfillment of Henry's law for ozone as a metastable gas is conditional. The decomposition of ozone in the gas phase depends on the partial pressure. In the aquatic environment, processes occur that go beyond the scope of Henry's law. Instead, under ideal conditions, the Gibs-Dukem-Margulesdu law applies. In practice, it is customary to express the solubility of ozone in water through the ratio of the concentration of ozone in a liquid medium to the concentration of ozone in the gas phase: Saturation with ozone depends on the temperature and quality of water, since organic and inorganic impurities change the pH of the medium. Under the same conditions, the ozone concentration in tap water is 13 mg/l, in double-distilled water - 20 mg/l. The reason for this is the significant decomposition of ozone due to various ionic impurities in drinking water.Ozone decay and half-life (t 1/2)
In an aquatic environment, ozone decomposition is highly dependent on water quality, temperature and pH of the environment. Increasing the pH of the environment accelerates the decomposition of ozone and thereby reduces the concentration of ozone in water. Similar processes occur with increasing temperature. The half-life of ozone in bidistilled water is 10 hours, in demineralized water - 80 minutes; in distilled water - 120 minutes. It is known that the decomposition of ozone in water is a complex process of reactions of radical chains:
The maximum amount of ozone in an aqueous sample is observed within 8-15 minutes. After 1 hour, only free oxygen radicals are observed in the solution. Among them, the most important is the hydroxyl radical (OH’) (Staehelin G., 1985), and this must be taken into account when using ozonated water for therapeutic purposes. Since ozonated water and ozonated saline solution are used in clinical practice, we assessed these ozonated liquids depending on the concentrations used in domestic medicine. The main methods of analysis were iodometric titration and chemiluminescence intensity using the BHL-06 biochemiluminometer device (manufactured in Nizhny Novgorod) (Kontorschikova K.N., Peretyagin S.P., Ivanova I.P. 1995). The phenomenon of chemiluminescence is associated with recombination reactions of free radicals formed during the decomposition of ozone in water. When 500 ml of bi- or distilled water is treated by bubbling an ozone-oxygen gas mixture with an ozone concentration in the range of 1000-1500 μg/l and a gas flow rate of 1 l/min for 20 minutes, chemiluminescence is detected within 160 minutes. Moreover, in bidistilled water the glow intensity is significantly higher than in distilled water, which is explained by the presence of impurities that dampen the glow. The solubility of ozone in NaCl solutions obeys Henry's law, i.e. decreases with increasing salt concentration. The saline solution was treated with ozone at concentrations of 400, 800 and 1000 μg/L for 15 minutes. The total glow intensity (in mv) increased with increasing ozone concentration. The glow duration is 20 minutes. This is explained by the faster recombination of free radicals and hence the quenching of the glow due to the presence of impurities in the physiological solution. Despite the high oxidation potential, ozone has high selectivity, which is due to the polar structure of the molecule. Compounds containing free double bonds (-C=C-) react instantly with ozone. As a result, unsaturated fatty acids, aromatic amino acids and peptides, primarily those containing SH groups, are sensitive to the action of ozone. According to Krige (1953) (cited from Vieban R. 1994), the primary product of the interaction of the ozone molecule with bioorganic substrates is a 1-3 dipolar molecule. This reaction is the main one in the interaction of ozone with organic substrates at pH< 7,4.
Озонолиз проходит в доли секунды. В растворах скорость этой реакции равна 105 г/моль·с. В первом акте реакции образуется пи-комплекс олефинов с озоном. Он относительно стабилен при температуре 140 0 С и затем превращается в первичный озонид (молозонид) 1,2,3-триоксалан. Другое possible direction reactions—formation of epoxy compounds. The primary ozonide is unstable and decomposes to form a carboxyl compound and carbonyl oxide. As a result of the interaction of carbonyl oxide with a carbonyl compound, a bipolar ion is formed, which is then converted into a secondary ozonide 1,2,3 - trioxalane. The latter, upon reduction, decomposes to form a mixture of 2 carbonyl compounds, with the further formation of peroxide (I) and ozonide (II). 
Ozonation of aromatic compounds occurs with the formation of polymeric ozonides. The addition of ozone disrupts the aromatic conjugation in the core and requires energy, therefore the rate of ozonation of homologues correlates with the conjugation energy. Ozonation of dried hydrocarbons is associated with the incorporation mechanism. Ozonation of sulfur- and nitrogen-containing organic compounds proceeds as follows: 
Ozonides are usually poorly soluble in water, but well soluble in organic solvents. When heated, transition metals decompose into radicals. The amount of ozonides in an organic compound is determined by the iodine number. Iodine number is the mass of iodine in grams added to 100 g of organic matter. Normally, the iodine number for fatty acids is 100-400, for solid fats 35-85, for liquid fats - 150-200. Ozone was first tested as an antiseptic by A. Wolff back in 1915 during the First World War. In subsequent years, information gradually accumulated on the successful use of ozone in the treatment of various diseases. However, for a long time, only ozone therapy methods associated with direct contact of ozone with external surfaces and various body cavities were used. Interest in ozone therapy increased as data accumulated on the biological effects of ozone on the body and reports appeared from various clinics around the world about the successful use of ozone in the treatment of a number of diseases. The history of medical use of ozone dates back to the 19th century. The pioneers of the clinical use of ozone were Western scientists in America and Europe, in particular, C. J. Kenworthy, B. Lust, I. Aberhart, E. Payer, E. A. Fisch, N. N. Wolff and others. In Russia, little was known about the therapeutic use of ozone. Only in the 60-70s Russian literature Several works appeared on inhalation ozone therapy and on the use of ozone in the treatment of certain skin diseases, and since the 80s in our country this method began to be intensively developed and became more widespread. The basis for the fundamental development of ozone therapy technologies was largely determined by the work of the Institute of Chemical Physics of the USSR Academy of Medical Sciences. The book “Ozone and its reactions with organic substances” (S.D. Razumovsky, G.E. Zaikov, Moscow, 1974) was the starting point for many developers to substantiate the mechanisms of the therapeutic effect of ozone. The International Ozone Association (IOA) is widely active in the world, which has held 20 international congresses, and since 1991, our doctors and scientists have taken part in the work of these congresses. Today, the problems of the applied use of ozone, namely in medicine, are being considered in a completely new way. In the therapeutic range of concentrations and doses, ozone exhibits the properties of a powerful bioregulator, a remedy that can greatly enhance the methods of traditional medicine, and often act as a monotherapy agent. The use of medical ozone represents a qualitatively new solution current problems treatment of many diseases. Ozone therapy technologies are used in surgery, obstetrics and gynecology, dentistry, neurology, therapeutic pathology, infectious diseases, dermatology and venereal diseases and a number of other diseases. Ozone therapy is characterized by ease of implementation, high efficiency, good tolerability, virtually no side effects, and it is cost-effective. The healing properties of ozone for diseases of various etiologies are based on its unique ability to affect the body. Ozone in therapeutic doses acts as an immunomodulatory, anti-inflammatory, bactericidal, antiviral, fungicidal, cytostatic, anti-stress and analgesic agent. Its ability to actively correct disturbed oxygen homeostasis of the body opens up great prospects for restorative medicine. A wide range of methodological capabilities allows you to use them with great efficiency medicinal properties ozone for local and systemic therapy. In recent decades, methods associated with parenteral (intravenous, intramuscular, intra-articular, subcutaneous) administration of therapeutic doses of ozone have come to the fore, the therapeutic effect of which is mainly associated with the activation of various vital systems of the body. An oxygen-ozone gas mixture with high (4000 - 8000 μg/l) concentrations of ozone in it is effective in treating heavily infected, poorly healing wounds, gangrene, bedsores, burns, fungal skin infections, etc. Ozone in high concentrations can also be used as a hemostatic agent. Low concentrations of ozone stimulate repair, promote epithelialization and healing. In the treatment of colitis, proctitis, fistulas and a number of other intestinal diseases, rectal administration of an oxygen-ozone gas mixture is used. Ozone dissolved in physiological solution is successfully used for peritonitis for sanitation of the abdominal cavity, and ozonized distilled water in jaw surgery, etc. For intravenous administration, ozone dissolved in physiological solution or in the patient’s blood is used. The pioneers of the European School postulated that the main goal of ozone therapy is: “Stimulation and reactivation of oxygen metabolism without disrupting redox systems,” this means that when calculating dosages per session or course, the ozone therapeutic effect should be within the limits in which radical oxygen metabolites or excessively produced peroxide are enzymatically leveled” (3 Rilling, R. Feeban 1996 in the book Practice of ozone therapy). In foreign medical practice, parenteral administration of ozone mainly uses major and minor autohemotherapy. When carrying out major autohemotherapy, blood taken from a patient is thoroughly mixed with a certain volume of oxygen-ozone gas mixture and immediately injected drip-wise back into the vein of the same patient. In minor autohemotherapy, ozonated blood is injected intramuscularly. The therapeutic dose of ozone in this case is maintained due to fixed volumes of gas and ozone concentration in it. Scientific achievements of domestic scientists began to be regularly reported at international congresses and symposia
- 1991 – Cuba, Havana,
- 1993 – USA San Francisco,
- 1995 – France Lille,
- 1997 – Japan, Kyoto,
- 1998 – Austria, Salzburg,
- 1999 – Germany, Baden-Baden,
- 2001 – England, London,
- 2005 – France, Strasbourg,
- 2009 – Japan, Kyoto,
- 2010 - Spain, Madrid
- 2011 Turkey (Istanbul), France (Paris), Mexico (Cancun)
- 2012 - Spain Madrid
All-Russian scientific and practical conferences with international participation on ozone therapy
I – “OZONE IN BIOLOGY AND MEDICINE” – 1992., N. Novgorod II – “OZONE IN BIOLOGY AND MEDICINE” – 1995., N. Novgorod III – “OZONE AND METHODS OF EFFERENT THERAPY” – 1998., N. Novgorod IV – “OZONE AND METHODS OF EFFERENT THERAPY” – 2000 g., N. Novgorod V – “OZONE IN BIOLOGY AND MEDICINE” – 2003., N. Novgorod VI – “OZONE IN BIOLOGY AND MEDICINE” – 2005., N. Novgorod“I Conference on Ozone Therapy of the Asian-European Union of Ozone Therapists and Medical Equipment Manufacturers” – 2006., Bolshoye Boldino, Nizhny Novgorod region VII – “OZONE IN BIOLOGY AND MEDICINE” – 2007., N. Novgorod U111 – “Ozone, reactive oxygen species and methods of intensive therapy in medicine” - 2009, Nizhny Novgorod By 2000, the Russian school of ozone therapy had finally formed its own approach to the use of ozone as a therapeutic agent, which differs from the European one. The main differences are the widespread use of saline as a carrier of ozone, the use of significantly lower concentrations and doses of ozone, developed technologies for extracorporeal processing of large volumes of blood (ozonated artificial circulation), individual choice of doses and concentrations of ozone during systemic ozone therapy. The desire of most Russian doctors to use the lowest effective concentrations of ozone reflects the basic principle of medicine - “do no harm.” The safety and effectiveness of Russian methods of ozone therapy have been repeatedly substantiated and proven in relation to various fields of medicine. As a result of many years of fundamental clinical research, Nizhny Novgorod scientists have established an unknown pattern in the formation of adaptive mechanisms of the mammalian body under systemic exposure to low therapeutic doses of ozone, which consists in the fact that the triggering mechanism is the influence of ozone on the pro- and antioxidant balance of the body and is caused by a moderate intensification of free- radical reactions, which, in turn, increases the activity of the enzymatic and non-enzymatic components of the antioxidant defense system" (Kontorschikova K.N., Peretyagin S.P.), for which the authors received a discovery (Diploma No. 309 dated May 16, 2006). In the works of domestic scientists, new technologies and aspects of the use of ozone for medicinal purposes have been developed:- Widespread use of physiological solution (0.9% NaCl solution) as a carrier of dissolved ozone
- The use of relatively small concentrations and doses of ozone for systemic exposure (intravascular and intraintestinal administration)
- Intraosseous infusions of ozonated solutions
- Intracoronary administration of ozonated cardioplegic solutions
- Total extracorporeal ozone treatment large volumes blood during artificial circulation
- Low-flow ozone-oxygen therapy
- Intraportal administration of ozonated solutions
- Use of ozone in the theater of operations
- Accompanying systemic ozone therapy with biochemical control methods
- Ozone therapy is a non-drug method of therapeutic intervention that allows one to obtain positive results in pathologies of various origins.
- The biological effect of parenterally administered ozone manifests itself at the level of low concentrations and doses, which is accompanied by clinically pronounced positive therapeutic effects that have a clearly defined dose dependence.
- The experience of the Russian and European schools of ozone therapy indicates that the use of ozone as a therapeutic agent significantly increases the effectiveness of drug therapy and allows, in some cases, to replace or reduce the pharmacological burden on the patient. Against the background of ozone therapy, the sick body's own oxygen-dependent reactions and processes are restored.
- The technical capabilities of modern medical ozonizers, which have ultra-precise dosage capabilities, allow the use of ozone in the range of low therapeutic concentrations, similar to conventional pharmacological agents.
Ozone is a gas. Unlike many others, it is not transparent, but has a characteristic color and even smell. It is present in our atmosphere and is one of its most important components. What is the density of ozone, its mass and other properties? What is its role in the life of the planet?
Blue gas
In chemistry, ozone does not have a separate place in the periodic table. This is because it is not an element. Ozone is an allotropic modification or variation of oxygen. Like O2, its molecule consists only of oxygen atoms, but it has not two, but three. Therefore, its chemical formula looks like O3.
Ozone is a blue gas. It has a clearly noticeable, pungent odor reminiscent of chlorine if the concentration is too high. Do you remember the smell of freshness when it rains? This is ozone. Thanks to this property, it got its name, because from the ancient Greek language “ozone” means “smell”.
The gas molecule is polar, the atoms in it are connected at an angle of 116.78°. Ozone is formed when a free oxygen atom attaches to an O2 molecule. This happens during various reactions, for example, oxidation of phosphorus, electrical discharge or decomposition of peroxides, during which oxygen atoms are released.
Properties of ozone
Under normal conditions, ozone exists with a molecular weight of almost 48 g/mol. It is diamagnetic, meaning it is not able to be attracted to a magnet, just like silver, gold or nitrogen. The ozone density is 2.1445 g/dm³.
In the solid state, ozone acquires a bluish-black color; in the liquid state, it becomes indigo, close to violet. The boiling point is 111.8 degrees Celsius. At a temperature of zero degrees, it dissolves in water (only clean water) ten times better than oxygen. It mixes well with nitrogen, fluorine, argon, and under certain conditions with oxygen.
Under the influence of a number of catalysts, it is easily oxidized, releasing free oxygen atoms. Connecting with it, it immediately ignites. The substance is capable of oxidizing almost all metals. Only platinum and gold are not affected by it. It destroys various organic and aromatic compounds. On contact with ammonia, it forms ammonium nitrite and destroys double carbon bonds.
Present in the atmosphere in high concentrations, ozone spontaneously decomposes. In this case, heat is released and an O2 molecule is formed. The higher its concentration, the stronger the heat release reaction. When the ozone content is more than 10%, it is accompanied by an explosion. When the temperature increases and the pressure decreases or when it comes into contact with organic matter, O3 decomposes faster.
History of discovery
Ozone was not known in chemistry until the 18th century. It was discovered in 1785 thanks to the smell that physicist Van Marum heard next to a working electrostatic machine. Another 50 years later it did not appear in any way in scientific experiments and research.
Scientist Christian Schönbein studied the oxidation of white phosphorus in 1840. During his experiments, he managed to isolate an unknown substance, which he called “ozone.” The chemist began to closely study its properties and described methods for obtaining the newly discovered gas.
Soon other scientists joined the research of the substance. The famous physicist Nikola Tesla even built the first in history. Industrial use of O3 began at the end of the 19th century with the advent of the first installations for supplying drinking water to homes. The substance was used for disinfection.
Ozone in the atmosphere
Our Earth is surrounded by an invisible shell of air - the atmosphere. Without it, life on the planet would be impossible. Components of atmospheric air: oxygen, ozone, nitrogen, hydrogen, methane and other gases.
Ozone itself does not exist and appears only as a result chemical reactions. Close to the Earth's surface, it is formed by electrical discharges from lightning during a thunderstorm. It appears unnaturally due to exhaust emissions from cars, factories, gasoline evaporations, and the action of thermal power plants.
Ozone in the lower layers of the atmosphere is called ground-level or tropospheric ozone. There is also a stratospheric one. It occurs under the influence of ultraviolet radiation coming from the Sun. It is formed at a distance of 19-20 kilometers above the surface of the planet and stretches to a height of 25-30 kilometers.
Stratospheric O3 forms the planet's ozone layer, which protects it from powerful solar radiation. It absorbs approximately 98% of ultraviolet radiation at a wavelength sufficient to cause cancer and burns.
Application of the substance
Ozone is an excellent oxidizer and destroyer. This property has long been used to purify drinking water. The substance has a detrimental effect on bacteria and viruses that are dangerous to humans, and upon oxidation it itself turns into harmless oxygen.
It can kill even chlorine-resistant organisms. In addition, it is used to purify wastewater from environmentally harmful petroleum products, sulfides, phenols, etc. Such practices are common mainly in the United States and some European countries.
Ozone is used in medicine to disinfect instruments; in industry, it is used to bleach paper, purify oils, and produce various substances. The use of O3 for air, water and room purification is called ozonation.
Ozone and man
Despite all its beneficial properties, ozone can be dangerous to humans. If there is more gas in the air than a person can tolerate, poisoning cannot be avoided. In Russia, its permissible limit is 0.1 μg/l.
When this norm is exceeded, typical signs of chemical poisoning appear, such as headache, irritation of the mucous membranes, and dizziness. Ozone reduces the body's resistance to infections transmitted through the respiratory tract, and also reduces blood pressure. At gas concentrations above 8-9 µg/l, pulmonary edema and even death are possible.
At the same time, it is quite easy to recognize ozone in the air. The smell of “freshness”, chlorine or “crayfish” (as Mendeleev claimed) is clearly audible even with a low content of the substance.
GENERAL INFORMATION.
Ozone - O3, an allotropic form of oxygen, is a powerful oxidizer of chemicals and other pollutants that are destroyed on contact. Unlike the oxygen molecule, the ozone molecule consists of three atoms and has longer bonds between the oxygen atoms. In terms of its reactivity, ozone ranks second, second only to fluorine.
History of discovery
In 1785, the Dutch physicist Van Ma-rum, conducting experiments with electricity, drew attention to the smell during the formation of sparks in an electric machine and to the oxidizing properties of air after electric sparks were passed through it.
In 1840, the German scientist Sheinbein, while hydrolyzing water, tried to split it into oxygen and hydrogen using an electric arc. And then he discovered that a new gas, hitherto unknown to science, had formed with a specific odor. The name “ozone” was assigned to the gas by Sheinbein because of its characteristic odor and comes from the Greek word “ozien”, which means “to smell”.
On September 22, 1896, inventor N. Tesla patented the first ozone generator.Physical properties of ozone.
Ozone can exist in all three states of aggregation. Under normal conditions, ozone is a bluish gas. The boiling point of ozone is 1120C, and the melting point is 1920C.
Due to its chemical activity, ozone has a very low maximum permissible concentration in the air (comparable to the maximum permissible concentration of chemical warfare agents) 5·10-8% or 0.1 mg/m3, which is 10 times the olfactory threshold for humans.Chemical properties of ozone.
First of all, two main properties of ozone should be noted:
Ozone, unlike atomic oxygen, is a relatively stable compound. It decomposes spontaneously at high concentrations, and the higher the concentration, the faster the rate of decomposition reaction. At ozone concentrations of 12-15%, ozone can decompose explosively. It should also be noted that the process of ozone decomposition accelerates with increasing temperature, and the decomposition reaction itself 2O3>3O2 + 68 kcal is exothermic and is accompanied by the release of a large amount of heat.
O3 -> O + O 2
O3 + O -> 2 O2
O2 + E- -> O2-Ozone is one of the strongest natural oxidizing agents. The oxidation potential of ozone is 2.07 V (for comparison, fluorine has 2.4 V, and chlorine has 1.7 V).
Ozone oxidizes all metals except gold and the platinum group, oxidizes sulfur and nitrogen oxides, and oxidizes ammonia to form ammonium nitrite.
Ozone actively reacts with aromatic compounds, destroying the aromatic nucleus. In particular, ozone reacts with phenol to destroy the nucleus. Ozone actively interacts with saturated hydrocarbons with the destruction of double carbon bonds.
The interaction of ozone with organic compounds is widely used in chemical industry and in related industries. The reactions of ozone with aromatic compounds formed the basis of deodorization technologies for various environments, premises and wastewater.Biological properties of ozone.
Despite a large number of studies, the mechanism is not well understood. It is known that at high concentrations of ozone, damage to the respiratory tract, lungs and mucous membranes is observed. Long-term exposure to ozone leads to the development of chronic diseases of the lungs and upper respiratory tract.
Exposure to small doses of ozone has a preventive and therapeutic effect and is beginning to be actively used in medicine - primarily for dermatology and cosmetology.
In addition to its great ability to destroy bacteria, ozone is highly effective in destroying spores, cysts (dense membranes that form around unicellular organisms, such as flagellates and rhizomes, during their reproduction, as well as in unfavorable conditions for them) and many other pathogenic microbes.Technological applications of ozone
Over the past 20 years, the applications of ozone have expanded significantly and new developments are underway around the world. Such rapid development of technologies using ozone is facilitated by its environmental cleanliness. Unlike other oxidizing agents, ozone decomposes during reactions into molecular and atomic oxygen and saturated oxides. All these products are generally non-polluting environment and do not lead to the formation of carcinogenic substances as, for example, during oxidation with chlorine or fluorine.Water:
In 1857, with the help of the “perfect magnetic induction tube” created by Werner von Siemens, the first technical ozone installation was built. In 1901, Siemens built the first hydroelectric power station with an ozone generator in Wiesband.
Historically, the use of ozone began with drinking water treatment plants, when the first pilot plant was tested in the city of Saint Maur (France) in 1898. Already in 1907, the first water ozonation plant was built in the city of Bon Voyage (France) for the needs of the city of Nice. In 1911, an ozonation station for drinking water was put into operation in St. Petersburg.
Currently, 95% of drinking water in Europe is treated with ozone. In the USA, the process of converting from chlorination to ozonation is underway. There are several large stations in Russia (in Moscow, Nizhny Novgorod and other cities).Air:
The use of ozone in water purification systems has been proven to be highly effective, but equally effective and proven safe air purification systems have not yet been created. Ozonation is considered a non-chemical cleaning method and is therefore popular among the population. However, the chronic effects of micro-concentrations of ozone on the human body have not been sufficiently studied.
With a very low concentration of ozone, the air in the room feels pleasant and fresh, and unpleasant odors are much less noticeable. Contrary to the popular belief about the beneficial effects of this gas, which is attributed in some brochures to ozone-rich forest air, in reality ozone, even when highly diluted, is a very toxic and dangerous irritant gas. Even small concentrations of ozone can have an irritating effect on mucous membranes and cause disorders of the central nervous system, which leads to bronchitis and headaches.Medical uses of ozone
In 1873, Focke observed the destruction of microorganisms under the influence of ozone, and this unique property of ozone attracted the attention of doctors.
The history of the use of ozone for medical purposes dates back to 1885, when Charlie Kenworth first published his report in the Florida Medical Association, USA. Brief information the use of ozone in medicine was discovered before this date.
In 1911, M. Eberhart used ozone in the treatment of tuberculosis, anemia, pneumonia, diabetes and other diseases. A. Wolf (1916) during the First World War used an oxygen-ozone mixture in the wounded for complex fractures, phlegmon, abscesses, and purulent wounds. N. Kleinmann (1921) used ozone for the general treatment of “body cavities”. In the 30s 20th century E.A. Fish, a dentist, begins ozone treatment in practice.
In the application for the invention of the first laboratory device, Fish proposed the term "CYTOZON", which is still listed on ozone generators used in dental practice today. Joachim Hänzler (1908-1981) created the first medical ozone generator, which allowed precise dosing of the ozone-oxygen mixture, and thus made it possible to widely use ozone therapy.
R. Auborg (1936) revealed the effect of scarring of colon ulcers under the influence of ozone and drew attention to the nature of its general effect on the body. Work on studying the therapeutic effects of ozone during the Second World War actively continued in Germany; the Germans successfully used ozone for local treatment of wounds and burns. However, after the war, research was interrupted for almost two decades, due to the advent of antibiotics and the lack of reliable, compact ozone generators and ozone-resistant materials. Extensive and systematic research in the field of ozone therapy began in the mid-70s, when ozone-resistant polymer materials and easy-to-use ozonation units appeared in everyday medical practice.
Research in vitro , that is, under ideal laboratory conditions, they showed that when interacting with the cells of the body, ozone oxidizes fats and forms peroxides - substances that are harmful to all known viruses, bacteria and fungi. In terms of its action, ozone can be compared to antibiotics, with the difference that it does not damage the liver and kidneys and has no side effects. But unfortunately, in vivo - in real conditions everything is much more complicated.
Ozone therapy was very popular at one time - many considered ozone almost a panacea for all ailments. But a detailed study of the effects of ozone showed that along with the sick, ozone also affects healthy cells of the skin and lungs. As a result, unexpected and unpredictable mutations begin in living cells. Ozone therapy never took root in Europe, and in the USA and Canada the official medical use of ozone is not legalized, with the exception of alternative medicine.
In Russia, unfortunately, official medicine has not abandoned such a dangerous and insufficiently proven method of therapy. Currently, air ozonizers and ozonizer units are widely used. Small ozone generators are used in the presence of people.OPERATING PRINCIPLE.
Ozone is formed from oxygen. There are several ways to produce ozone, the most common of which are: electrolytic, photochemical and electrosynthesis in gas discharge plasma. In order to avoid unwanted oxides, it is preferable to obtain ozone from pure medical oxygen using electrosynthesis. The concentration of the resulting ozone-oxygen mixture in such devices is easy to vary - either by setting a certain power of the electrical discharge, or by regulating the flow of incoming oxygen (the faster the oxygen passes through the ozonizer, the less ozone is formed).Electrolytic The ozone synthesis method is carried out in special electrolytic cells. Solutions of various acids and their salts (H2SO4, HClO4, NaClO4, KClO4) are used as electrolytes. The formation of ozone occurs due to the decomposition of water and the formation of atomic oxygen, which, when added to an oxygen molecule, forms ozone and a hydrogen molecule. This method produces concentrated ozone, but it is very energy intensive and is therefore not widely used.
Photochemical The method of producing ozone is the most common method in nature. Ozone is formed when an oxygen molecule dissociates under the influence of short-wave UV radiation. This method does not produce high concentration ozone. Devices based on this method have become widespread for laboratory purposes, in medicine and the food industry.
Electrosynthesis ozone is most widespread. This method combines the ability to obtain high concentrations of ozone with high productivity and relatively low energy costs.
As a result of numerous studies on the use of various types of gas discharge for ozone electrosynthesis, devices using three forms of discharge have become widespread:
- Barrier discharge - most widely used, is a large set of pulsed microdischarges in a gas gap 1-3 mm long between two electrodes separated by one or two dielectric barriers when the electrodes are powered by alternating voltage high voltage frequency from 50 Hz to several kilohertz. The productivity of one installation can range from grams to 150 kg of ozone per hour.
- Surface discharge - close in shape to a barrier discharge, which has become widespread in the last decade due to its simplicity and reliability. It is also a set of microdischarges developing along the surface of a solid dielectric when the electrodes are powered with alternating voltage with a frequency of 50 Hz to 15-40 kHz.
- Pulse discharge - as a rule, a streamer corona discharge that occurs in the gap between two electrodes when the electrodes are powered with a pulse voltage lasting from hundreds of nanoseconds to several microseconds.
- Effective in cleaning indoor air.
- Do not produce harmful by-products.
- Facilitates conditions for allergy sufferers, asthmatics, etc.
In 1997, ozonizer manufacturing companies Living Air Corporation, Alpine Industries Inc. (now “Ecoguest”), Quantum Electronics Corp. and others who violated the US FTC order were administratively punished by the courts, including a ban on further activities some of them in the United States. At the same time, private entrepreneurs who sold ozone generators with recommendations for using them in rooms with people received prison sentences ranging from 1 to 6 years.
Currently, some of these Western companies are successfully developing active sales of their products in Russia.Disadvantages of ozonizers:
Any sterilization system using ozone requires careful safety monitoring, testing of ozone concentration constants with gas analyzers, and emergency management of excessive ozone concentrations.
The ozonizer is not designed to work in:
- environment saturated with electrically conductive dust and water vapor,
- places containing active gases and vapors that destroy metal,
- places with relative humidity above 95%,
- in explosion and fire hazardous areas.
Application of ozonizers for indoor air sterilization:
- lengthens the time of the sterilization process,
- increases toxicity and oxidation of the air,
- leads to a danger of explosion,
- The return of people to a disinfected room is possible only after the ozone has completely decomposed.
SUMMARY.
Ozonation is highly effective for sterilizing surfaces and indoor air, but there is no effect of purifying the air from mechanical impurities. The impossibility of using the method in the presence of people and the need to carry out disinfection in a sealed room seriously limits the scope of its professional application.
How is ozone useful?
Ozone, being a strong oxidizing agent, is widely used in various areas of our life. It is used in medicine, in industry, in everyday life
What kind of gas is ozone?
During a thunderstorm, when electrical discharges of lightning “pierce” the atmosphere, we feel the resulting ozone as fresh air. Ozone really cleans our air! Being a strong oxidizing agent, it decomposes many toxic impurities in the atmosphere into simple safe compounds, thereby disinfecting the air. That’s why after a thunderstorm we feel pleasantly fresh, we can breathe easily, and we see everything around us more clearly, especially the blue of the sky.
Ozone is a blue gas with a characteristic odor and a very strong oxidizing agent. The molecular formula of ozone is O3. It is heavier than oxygen and our usual air.
The formation of ozone is as follows: Under the influence of an electric discharge, some oxygen molecules O2 disintegrate into atoms, then atomic oxygen combines with molecular oxygen and ozone O3 is formed. In nature, ozone is formed in the stratosphere under the influence of ultraviolet radiation from the Sun, as well as during electrical discharges in the atmosphere.
Household ozonation devices provide a safe concentration of ozone for humans. With help you will always breathe fresh and clean air
Where is ozone used today?
It is such a strong oxidizing agent that it can stimulate redox processes in the human body, and this is the essence of life. It enhances the function of the immune system two to four times. OZONE is a natural antibiotic! When interacting with the cells of the body, it oxidizes fats and forms peroxides - substances that are destructive to all known viruses, bacteria and fungi.Most common application- for water purification. Ozone effectively destroys bacteria and viruses, eliminates organic water contaminants, eliminates odors, can
be used as a bleaching agent.
Special role allocated to ozone in the food industry. A highly disinfectant and chemically safe agent, it is used to prevent the biological growth of unwanted organisms in food products
and on food processing equipment. Ozone has the ability to kill microorganisms without creating new harmful chemicals.
All chemicals that are in the air, reacting with ozone, break down into harmless compounds: carbon dioxide, water and oxygen.
What is it needed for ?
- Air purification in living areas, bathrooms and toilets.
- Elimination of unpleasant odors in the refrigerator, wardrobes, pantries, etc.
- Purification of drinking water, ozonation of bathtubs, aquariums.
- Food processing (vegetables, fruits, eggs, meat, fish).
- Disinfection and elimination of dirt and unpleasant odors when washing clothes.
- Cosmetology procedures, care for the oral cavity, facial skin, hands and feet.
- Eliminating the smell of tobacco smoke, paint, varnish
Ozone in medicine
Ozone in therapeutic doses acts as an immunomodulatory, anti-inflammatory, bactericidal, antiviral, fungicidal, cystostatic, anti-stress and analgesic agent.
Ozone therapy is successfully used in almost all areas of medicine: in emergency and purulent surgery, general and infectious therapy, gynecology, urology,
dermatology, hepatology, gastroenterology, dentistry, cosmetology, etc.
What are the effects of ozone therapy?
- Activation of detoxification processes. The activity of external and internal toxins is suppressed.
- Activation of metabolic processes (metabolic processes).
- Normalization of the process of lipid peroxidation (fat metabolic processes).
The use of ozone increases the consumption of glucose by tissues and organs, increases the saturation of blood plasma with oxygen, reduces the degree of oxygen starvation,
improves microcirculation.
Ozone has a positive effect on the metabolism of the liver and kidneys, supports the functioning of the heart muscle, reduces the respiratory rate and increases tidal volume.
Positive influence ozone for people with diseases of the cardiovascular system (the level of cholesterol in the blood decreases, the risk of blood clots decreases, and the process of cell “breathing” is activated).
Ozone therapy for treatment herpes allows you to significantly reduce the course and dose of antiviral drugs.
At decreased immunity Ozone therapy stimulates the body's resistance to diseases such as flu, sore throat, ARVI, acute respiratory infections so popular in the autumn-winter period.
In case of illness" chronic fatigue syndrome caused by cytomegalovirus And herpes virus, ozone therapy helps get rid of headaches, fatigue, increases performance and overall vitality. Ozone therapy gives the same effect in the treatment of ordinary fatigue, chronic lack of sleep, overwork, almost instantly relieving the syndromes.
Ozone therapy (autohemotherapy with ozone) is widely used in cosmetology For wrinkle correction general "rejuvenation" of the skin, treatment of problem skin and acne, including teenage acne, acne.
With the help of ozone, extra pounds are lost! In order to lose weight, cure cellulite and remove volume on the abdomen, hips, and buttocks, systemic and local use of ozone is recommended.
Are there any contraindications to the use of ozone therapy?
Yes, there are contraindications. Therefore, be very careful when prescribing ozone therapy, consult your doctor, discuss the methods and methods of influence, possible reactions of the body.
Ozone therapy should not be used for acute myocardial infarction, internal bleeding, hyperthyroidism, a tendency to seizures, or thrombocytopenia.
Scientists first learned about the existence of an unknown gas when they began experimenting with electrostatic machines. This happened in the 17th century. But they began to study the new gas only at the end of the next century. In 1785, Dutch physicist Martin van Marum obtained ozone by passing electric sparks through oxygen. The name ozone appeared only in 1840; it was invented by the Swiss chemist Christian Schönbein, deriving it from the Greek ozon - smelling. The chemical composition of this gas did not differ from oxygen, but it was much more aggressive. Thus, it instantly oxidized colorless potassium iodide, releasing brown iodine; Schönbein used this reaction to determine ozone by the degree of blueness of paper soaked in a solution of potassium iodide and starch. Even mercury and silver, which are inactive at room temperature, are oxidized in the presence of ozone.
It turned out that ozone molecules, like oxygen, consist only of oxygen atoms, but not two, but three. Oxygen O2 and ozone O3 are the only example of the formation of two gaseous (under normal conditions) simple substances by one chemical element. In the O3 molecule, the atoms are located at an angle, so these molecules are polar. Ozone is obtained as a result of the “sticking” of free oxygen atoms to O2 molecules, which are formed from oxygen molecules under the influence of electrical discharges, ultraviolet rays, gamma rays, fast electrons and other high-energy particles. There is always a smell of ozone near operating electric machines, in which brushes “spark,” and near bactericidal mercury-quartz lamps that emit ultraviolet light. Oxygen atoms are also released during certain chemical reactions. Ozone is formed in small quantities during the electrolysis of acidified water, during the slow oxidation of moist white phosphorus in air, during the decomposition of compounds with high content oxygen (KMnO4, K2Cr2O7, etc.), when water is exposed to fluorine or barium peroxide is exposed to concentrated sulfuric acid. Oxygen atoms are always present in the flame, so if you direct a stream of compressed air across the flame of an oxygen burner, the characteristic smell of ozone will be detected in the air.
The reaction 3O2 → 2O3 is highly endothermic: to obtain 1 mole of ozone, 142 kJ must be consumed. The reverse reaction occurs with the release of energy and is carried out very easily. Accordingly, ozone is unstable. In the absence of impurities, ozone gas decomposes slowly at a temperature of 70° C and quickly above 100° C. The rate of ozone decomposition increases significantly in the presence of catalysts. They can be gases (for example, nitric oxide, chlorine), and many solids (even the walls of a vessel). Therefore, pure ozone is difficult to obtain, and working with it is dangerous due to the possibility of explosion.
It is not surprising that for many decades after the discovery of ozone, even its basic physical constants were unknown: for a long time no one was able to obtain pure ozone. As D.I. Mendeleev wrote in his textbook Fundamentals of Chemistry, “with all methods of preparing ozone gas, its content in oxygen is always insignificant, usually only a few tenths of a percent, rarely 2%, and only at very low temperatures does it reach 20%.” Only in 1880 did the French scientists J. Gotfeil and P. Chappuis obtain ozone from pure oxygen at a temperature of minus 23 ° C. It turned out that in a thick layer ozone has a beautiful blue color. When the cooled ozonated oxygen was slowly compressed, the gas turned dark blue, and after quickly releasing the pressure, the temperature dropped even further and dark purple droplets of liquid ozone formed. If the gas was not cooled or compressed quickly, then the ozone instantly, with a yellow flash, turned into oxygen.
Later, a convenient method for ozone synthesis was developed. If a concentrated solution of perchloric, phosphoric or sulfuric acid is subjected to electrolysis with a cooled platinum or lead(IV) oxide anode, the gas released at the anode will contain up to 50% ozone. The physical constants of ozone were also refined. It liquefies much easier than oxygen - at a temperature of -112° C (oxygen - at -183° C). At –192.7° C ozone solidifies. Solid ozone is blue-black in color.
Experiments with ozone are dangerous. Ozone gas can explode if its concentration in the air exceeds 9%. Liquid and solid ozone explode even more easily, especially when in contact with oxidizing substances. Ozone can be stored at low temperatures in the form of solutions in fluorinated hydrocarbons (freons). Such solutions are blue in color.
Chemical properties of ozone.
Ozone is characterized by extremely high reactivity. Ozone is one of the strongest oxidizing agents and is second in this regard only to fluorine and oxygen fluoride OF2. The active principle of ozone as an oxidizing agent is atomic oxygen, which is formed during the decay of the ozone molecule. Therefore, acting as an oxidizing agent, the ozone molecule, as a rule, “uses” only one oxygen atom, and the other two are released in the form of free oxygen, for example, 2KI + O3 + H2O → I2 + 2KOH + O2. The oxidation of many other compounds also occurs. However, there are exceptions when the ozone molecule uses all three oxygen atoms it has for oxidation, for example, 3SO2 + O3 → 3SO3; Na2S + O3 → Na2SO3.
A very important difference between ozone and oxygen is that ozone exhibits oxidizing properties already at room temperature. For example, PbS and Pb(OH)2 do not react with oxygen under normal conditions, while in the presence of ozone, sulfide turns into PbSO4, and hydroxide into PbO2. If a concentrated ammonia solution is poured into a vessel containing ozone, White smoke– ozone oxidized ammonia to form ammonium nitrite NH4NO2. Particularly characteristic of ozone is the ability to “blacken” silver items with the formation of AgO and Ag2O3.
By adding one electron and becoming a negative O3– ion, the ozone molecule becomes more stable. “Ozone acid salts” or ozonides containing such anions have been known for a long time - they are formed by all alkali metals except lithium, and the stability of ozonides increases from sodium to cesium. Some ozonides of alkaline earth metals are also known, for example, Ca(O3)2. If a stream of ozone gas is directed onto the surface of a solid dry alkali, an orange-red crust containing ozonides is formed, for example, 4KOH + 4O3 → 4KO3 + O2 + 2H2O. At the same time, solid alkali effectively binds water, which protects ozonide from immediate hydrolysis. However, with an excess of water, ozonides decompose rapidly: 4KO3+ 2H2O → 4KOH + 5O2. Decomposition also occurs during storage: 2KO3 → 2KO2 + O2. Ozonides are highly soluble in liquid ammonia, which made it possible to isolate them in pure form and study their properties.
Organic substances that ozone comes into contact with are usually destroyed. Thus, ozone, unlike chlorine, is capable of splitting the benzene ring. When working with ozone, you cannot use rubber tubes and hoses - they will instantly become leaky. Reactions of ozone with organic compounds release large amounts of energy. For example, ether, alcohol, cotton wool soaked in turpentine, methane and many other substances spontaneously ignite when in contact with ozonated air, and mixing ozone with ethylene leads to a strong explosion.
Application of ozone.
Ozone does not always “burn” organic matter; in some cases it is possible to carry out specific reactions with highly dilute ozone. For example, when oleic acid is ozonated (it is found in large quantities in vegetable oils), azelaic acid HOOC(CH2)7COOH is formed, which is used to produce high-quality lubricating oils, synthetic fibers and plasticizers for plastics. Adipic acid is obtained similarly, which is used in the synthesis of nylon. In 1855, Schönbein discovered the reaction of unsaturated compounds containing double C=C bonds with ozone, but only in 1925 did the German chemist H. Staudinger establish the mechanism of this reaction. An ozone molecule attaches to a double bond to form an ozonide - this time organic, and an oxygen atom replaces one of the C=C bonds, and an –O–O– group takes the place of the other. Although some organic ozonides are isolated in pure form (for example, ethylene ozonide), this reaction is usually carried out in a dilute solution, since free ozonides are very unstable explosives. The ozonation reaction of unsaturated compounds is held in high esteem by organic chemists; Problems with this reaction are often offered even at school competitions. The fact is that when ozonide decomposes with water, two aldehyde or ketone molecules are formed, which are easy to identify and further establish the structure of the original unsaturated compound. Thus, chemists at the beginning of the 20th century established the structure of many important organic compounds, including natural ones, containing C=C bonds.
An important area of application of ozone is the disinfection of drinking water. Usually water is chlorinated. However, some impurities in water under the influence of chlorine turn into compounds with a very unpleasant odor. Therefore, it has long been proposed to replace chlorine with ozone. Ozonated water does not acquire any foreign smell or taste; When many organic compounds are completely oxidized by ozone, only carbon dioxide and water are formed. Ozone also purifies wastewater. Ozone oxidation products of even such pollutants as phenols, cyanides, surfactants, sulfites, chloramines are harmless, colorless and odorless compounds. Excess ozone disintegrates quite quickly to form oxygen. However, water ozonation is more expensive than chlorination; In addition, ozone cannot be transported and must be produced at the point of use.
Ozone in the atmosphere.
There is little ozone in the Earth's atmosphere - 4 billion tons, i.e. on average only 1 mg/m3. The concentration of ozone increases with distance from the Earth's surface and reaches a maximum in the stratosphere, at an altitude of 20–25 km - this is the “ozone layer”. If all the ozone from the atmosphere were collected at the Earth's surface at normal pressure, the resulting layer would be only about 2–3 mm thick. And such small amounts of ozone in the air actually support life on Earth. Ozone creates " protective screen", preventing hard ultraviolet rays from the sun, which are destructive for all living things, from reaching the surface of the Earth.
In recent decades, much attention has been paid to the appearance of so-called “ozone holes” - areas with significantly reduced levels of stratospheric ozone. Through such a “leaky” shield, harsher ultraviolet radiation from the Sun reaches the Earth’s surface. That's why scientists have been monitoring ozone in the atmosphere for a long time. In 1930, the English geophysicist S. Chapman, to explain the constant concentration of ozone in the stratosphere, proposed a scheme of four reactions (these reactions were called the Chapman cycle, in which M means any atom or molecule that carries away excess energy):
О2 → 2О
O + O + M → O2 + M
O + O3 → 2O2
O3 → O2 + O.
The first and fourth reactions of this cycle are photochemical, they occur under the influence of solar radiation. To decompose an oxygen molecule into atoms, radiation with a wavelength of less than 242 nm is required, while ozone disintegrates when light is absorbed in the region of 240–320 nm (the latter reaction precisely protects us from hard ultraviolet radiation, since oxygen does not absorb in this spectral region) . The remaining two reactions are thermal, i.e. go without the influence of light. It is very important that the third reaction, leading to the disappearance of ozone, has an activation energy; this means that the rate of such a reaction can be increased by the action of catalysts. As it turned out, the main catalyst for ozone decomposition is nitric oxide NO. It is formed in the upper layers of the atmosphere from nitrogen and oxygen under the influence of the harshest solar radiation. Once in the ozonosphere, it enters a cycle of two reactions O3 + NO → NO2 + O2, NO2 + O → NO + O2, as a result of which its content in the atmosphere does not change, and the stationary ozone concentration decreases. There are other cycles that lead to a decrease in ozone content in the stratosphere, for example, with the participation of chlorine:
Cl + O3 → ClO + O2
ClO + O → Cl + O2.
Ozone is also destroyed by dust and gases that enter the atmosphere in large quantities during volcanic eruptions. Recently, it has been suggested that ozone is also effective in destroying hydrogen released from earth's crust. The combination of all reactions of ozone formation and decay leads to the fact that the average lifetime of an ozone molecule in the stratosphere is about three hours.
It is believed that in addition to natural, there are also artificial factors that affect the ozone layer. Fine famous example– freons, which are sources of chlorine atoms. Freons are hydrocarbons in which hydrogen atoms are replaced by fluorine and chlorine atoms. They are used in refrigeration technology and for filling aerosol cans. Ultimately, freons enter the air and slowly rise higher and higher with air currents, finally reaching the ozone layer. Decomposing under the influence of solar radiation, freons themselves begin to catalytically decompose ozone. It is not yet known exactly to what extent freons are to blame for the “ozone hole”, and, nevertheless, measures have long been taken to limit their use.
Calculations show that in 60–70 years, the ozone concentration in the stratosphere may decrease by 25%. And at the same time, the concentration of ozone in the ground layer – the troposphere – will increase, which is also bad, since ozone and the products of its transformations in the air are poisonous. The main source of ozone in the troposphere is the transfer of stratospheric ozone with air masses to the lower layers. Every year, approximately 1.6 billion tons of ozone enter the ground layer. The lifetime of an ozone molecule in the lower part of the atmosphere is much longer - more than 100 days, since the intensity of ultraviolet solar radiation that destroys ozone is lower in the ground layer. Usually there is very little ozone in the troposphere: in clean fresh air its concentration averages only 0.016 μg/l. The concentration of ozone in the air depends not only on altitude, but also on terrain. Thus, there is always more ozone over the oceans than over land, since ozone decays more slowly there. Measurements in Sochi showed that the air near the sea coast contains 20% more ozone than in a forest 2 km from the coast.
Modern people inhale significantly more ozone than their ancestors. The main reason for this is the increase in the amount of methane and nitrogen oxides in the air. Thus, the content of methane in the atmosphere has been constantly increasing since the mid-19th century, when the use of natural gas began. In an atmosphere polluted with nitrogen oxides, methane enters into a complex chain of transformations with the participation of oxygen and water vapor, the result of which can be expressed by the equation CH4 + 4O2 → HCHO + H2O + 2O3. Other hydrocarbons can also act as methane, for example, those contained in car exhaust gases during incomplete combustion of gasoline. As a result, the concentration of ozone in the air of large cities has increased tenfold over the past decades.
It has always been believed that during a thunderstorm, the concentration of ozone in the air increases sharply, since lightning promotes the conversion of oxygen into ozone. In fact, the increase is insignificant, and it does not occur during a thunderstorm, but several hours before it. During a thunderstorm and for several hours after it, the ozone concentration decreases. This is explained by the fact that before a thunderstorm there is a strong vertical mixing of air masses, so that an additional amount of ozone comes from the upper layers. In addition, before a thunderstorm, the electric field strength increases, and conditions are created for the formation of a corona discharge at the tips of various objects, for example, the tips of branches. This also contributes to the formation of ozone. And then, as a thundercloud develops, powerful upward air currents arise beneath it, which reduce the ozone content directly below the cloud.
An interesting question is about the ozone content in the air of coniferous forests. For example, in the Course of Inorganic Chemistry by G. Remy, you can read that “ozonized air of coniferous forests” is a fiction. Is it so? Of course, no plant produces ozone. But plants, especially conifers, emit many volatile organic compounds into the air, including unsaturated hydrocarbons of the terpene class (there are many of them in turpentine). So, on a hot day, pine releases 16 micrograms of terpenes per hour for every gram of dry weight of needles. Terpenes are released not only by conifers, but also by some deciduous trees, including poplar and eucalyptus. And some tropical trees are capable of releasing 45 mcg of terpenes per 1 g of leaf dry weight per hour. As a result, one hectare of coniferous forest can release up to 4 kg of organic matter per day, and about 2 kg of deciduous forest. The forested area of the Earth is millions of hectares, and all of them emit hundreds of thousands of tons of various hydrocarbons, including terpenes, per year. And hydrocarbons, as was shown with the example of methane, under the influence of solar radiation and in the presence of other impurities contribute to the formation of ozone. As experiments have shown, terpenes, under suitable conditions, are indeed very actively involved in the cycle of atmospheric photochemical reactions with the formation of ozone. So ozone in a coniferous forest is not a fiction at all, but an experimental fact.
Ozone and health.
How nice it is to take a walk after a thunderstorm! The air is clean and fresh, its invigorating streams seem to flow into the lungs without any effort. “It smells like ozone,” they often say in such cases. “Very good for health.” Is it so?
Ozone was once considered beneficial to health. But if its concentration exceeds a certain threshold, it can cause a lot of unpleasant consequences. Depending on the concentration and time of inhalation, ozone causes changes in the lungs, irritation of the mucous membranes of the eyes and nose, headache, dizziness, and decreased blood pressure; Ozone reduces the body's resistance to bacterial respiratory tract infections. The maximum permissible concentration in the air is only 0.1 μg/l, which means that ozone is much more dangerous than chlorine! If you spend several hours in a room with an ozone concentration of only 0.4 μg/l, chest pain, cough, insomnia may appear, and visual acuity may decrease. If you breathe ozone for a long time at a concentration of more than 2 μg/l, the consequences can be more severe - even torpor and decline in cardiac activity. When the ozone content is 8–9 μg/l, pulmonary edema occurs within a few hours, which can be fatal. But such tiny amounts of a substance are usually difficult to analyze using conventional chemical methods. Fortunately, a person feels the presence of ozone even at very low concentrations - about 1 μg/l, at which starch iodine paper is not yet going to turn blue. To some people, the smell of ozone in low concentrations resembles the smell of chlorine, to others - to sulfur dioxide, to others - to garlic.
It's not just ozone itself that is toxic. With its participation in the air, for example, peroxyacetyl nitrate (PAN) CH3–CO–OONO2 is formed - a substance that has a strong irritant, including tear-producing, effect, making breathing difficult, and in higher concentrations causing cardiac paralysis. PAN is one of the components of the so-called photochemical smog formed in summer in polluted air (this word is derived from the English smoke - smoke and fog - fog). The ozone concentration in smog can reach 2 μg/l, which is 20 times more than the maximum permissible level. It should also be taken into account that the combined effect of ozone and nitrogen oxides in the air is tens of times stronger than each substance separately. It is not surprising that the consequences of such smog in large cities can be catastrophic, especially if the air above the city is not blown through by “drafts” and a stagnant zone is formed. Thus, in London in 1952, more than 4,000 people died from smog within a few days. And smog in New York in 1963 killed 350 people. There were similar stories in Tokyo and other large cities. It's not just people who suffer from atmospheric ozone. American researchers have shown, for example, that in areas with high levels of ozone in the air, the service life of car tires and other rubber products is significantly reduced.
How to reduce the ozone content in the ground layer? It is hardly realistic to reduce the release of methane into the atmosphere. There remains another way - to reduce emissions of nitrogen oxides, without which the cycle of reactions leading to ozone cannot proceed. This path is also not easy, since nitrogen oxides are emitted not only by cars, but also (mainly) by thermal power plants.
Sources of ozone are not only on the street. It is formed in X-ray rooms, in physiotherapy rooms (its source is mercury-quartz lamps), during the operation of copying equipment (copiers), laser printers (here the reason for its formation is a high-voltage discharge). Ozone is an inevitable companion to the production of perhydrol and argon-arc welding. To reduce the harmful effects of ozone, it is necessary to have ventilation equipment near ultraviolet lamps and good ventilation of the room.
And yet it is hardly correct to consider ozone as absolutely harmful to health. It all depends on its concentration. Studies have shown that fresh air glows very faintly in the dark; The cause of the glow is oxidation reactions involving ozone. The glow was also observed when shaking water in a flask into which ozonized oxygen had previously been introduced. This glow is always associated with the presence of small amounts of organic impurities in the air or water. When fresh air was mixed with a person’s exhaled breath, the intensity of the glow increased tenfold! And this is not surprising: microimpurities of ethylene, benzene, acetaldehyde, formaldehyde, acetone, and formic acid were found in the exhaled air. They are “highlighted” by ozone. At the same time, “stale”, i.e. completely devoid of ozone, although very clean, the air does not produce a glow, and a person perceives it as “musty.” Such air can be compared to distilled water: it is very clean, practically free of impurities, and drinking it is harmful. So the complete absence of ozone in the air, apparently, is also unfavorable for humans, since it increases the content of microorganisms in it and leads to the accumulation of harmful substances and unpleasant odors, which ozone destroys. Thus, it becomes clear the need for regular and long-term ventilation of rooms, even if there are no people in it: after all, ozone that enters a room does not stay in it for a long time - it partially disintegrates, and largely settles (adsorbs) on the walls and other surfaces. It is difficult to say how much ozone there should be in the room. However, in minimal concentrations, ozone is probably necessary and beneficial.
Ilya Leenson