Ozone , or trioxygen , is an inorganic molecule with the chemical formula O
3 . It is a pale blue gas with a distinctive stinging smell. This is a much less stable allotrope of oxygen than the allotropes of diatomic O
2 , crashes in the lower atmosphere to O
2 or dioxygen. Ozone is formed from dioxygen by the action of ultraviolet light and also the release of atmospheric electricity, and is present in very low concentrations throughout the Earth's atmosphere (the stratosphere). Its concentration is highest in the area of ​​the atmospheric ozone layer, which absorbs most of the solar ultraviolet (UV) radiation.
The ozone odor is sharp, reminiscent of chlorine, and can be detected by many people at concentrations as small as 100 ppb in the air. The structure of Ozone << sub> 3 was determined in 1865. This molecule was later shown to have a bent structure and became diamagnetic. Under standard conditions, ozone is a pale blue gas that condenses at progressive cryogenic temperatures into dark blue liquids and ultimately solid purple-black. The ozone instability associated with more common dioxygen is such that both concentrated gas and liquid ozone can decompose explosively at high temperatures or rapid warming to the boiling point. It is therefore used commercially only in low concentrations.
Ozone is a powerful oxidant (much better than dioxygen) and has many industrial and consumer applications associated with oxidation. This same high oxidizing potential, however, causes ozone to impair mucus and respiratory tissue in animals, as well as tissue in plants, above concentrations around 100Ã, ppb . This makes ozone a dangerous respiratory and potential pollutant near the soil surface. However, the ozone layer (part of the stratosphere with higher ozone concentrations, from two to eight ppm) is beneficial, preventing destructive ultraviolet rays reaching Earth's surface, for the benefit of plants and animals.
Video Ozone
Nomenklatur
The trivial name ozone is the most commonly used and preferred IUPAC name. Systematic name 2? 4 -trioxidiene
In the appropriate context, ozone can be seen as a trioxidane with two hydrogen atoms removed, and thus, trioxidanylidene can be used as a contextual-specific systematic name, according to the alternate nomenclature. By default, these names do not concern the radicality of ozone molecules. Even in a more specific context, it can also denote the underlying state of the non-radical singletons, while the predicted state is trioxidanediyl .
Trioxidanediyl (or ozonide ) is used, not systematically, to refer to the substituent group (-OOO-). Care should be taken to avoid confusing the group name for a specific context name for the ozone given above.
Maps Ozone
History
In 1785, the Dutch chemist Martinus van Marum was conducting an experiment involving electric sparks on the water when he noticed an unusual odor, which he connected with an electrical reaction, failed to realize that he had actually created ozone.
Half a century later, Christian Friedrich SchÃÆ'Âbebein noticed the same pungent odor and recognized it as the odor often following the lightning. In 1839, he isolated the gas chemicals and named them "ozone", from the Greek word ozein ( ????? ) which means "smell". For this reason, SchÃÆ'¶nbein is generally credited with the discovery of ozone. The formula for ozone, O 3 , was not determined until 1865 by Jacques-Louis Soret and confirmed by SchÃÆ'¶nbein in 1867.
For much of the second half of the nineteenth century and far into the 20th century, ozone is considered a component of a healthy environment by naturalists and health seekers. Beaumont, California has the official slogan "Beaumont: Zone of Ozone", as evidenced on postcards and letterheads of the Chamber of Commerce. Naturalists who work outdoors often assume a higher elevation is beneficial because of their ozone content. "There is a very different atmosphere [at higher altitudes] with enough ozone to maintain the necessary energy [to work]", writes naturalist Henry Henshaw, who works in Hawaii. The air by the sea is considered healthy because it is believed to contain ozone; but this creeping odor is the fact that the metabolism of seaweed is halogenated.
Much of the attraction of ozone appears to result from its "fresh" smell, which evokes associations with purification properties. Scientists, however, noted its harmful effects. In 1873 James Dewar and John Gray McKendrick documented that frogs grew slowly, panting birds, and rabbit blood showed a decrease in oxygen levels after exposure to "ozonized air", which "carried out destructive actions". SchÃÆ'¶nbein himself reported that chest pain, mucous membrane irritation and breathing difficulties occur as a result of inhaling ozone, and small mammals die. In 1911, Leonard Hill and Martin Flack stated in the Proceedings of the Royal Society that a healthy ozone effect had, by just iteration, been part and parcel of the common beliefs, and not necessarily the physiological evidence support of its good effects to date almost entirely desires... The only very definite knowledge of the physiological effects of ozone, so far achieved, is that it causes irritation and pulmonary edema, and death if inhaled in relatively strong concentrations for any time. "
During World War I, ozone was tested at the Queen Alexandra Military Hospital in London as a possible disinfectant for injuries. The gas was immediately applied to the wound for 15 minutes. This results in damage to both bacterial cells and human tissue. Other sanitation techniques, such as irrigation with antiseptics, are found to be better.
Physical properties
Colorless ozone or pale blue gas (blue when liquefied), slightly soluble in water and much more soluble in non-inert polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution. At 161Ã, Â ° K (-112Ã, Â ° C; -170Ã, Â ° F), condenses to form a dark blue liquid. It is very dangerous to allow this liquid to warm to its boiling point, since both concentrated ozone gas and liquid ozone can erupt. At temperatures below 80 ° K (-193.2 ° C; -315.7 ° F), it forms a purple-purple solid.
Most people can detect about 0.01? Mol/mol ozone in the air where it has a very specific sharp odor similar to chlorine bleach. Exposure 0.1 to 1? Mol/mol produces headaches, burning eyes and irritation of the respiratory tract. Even low concentrations of ozone in the air greatly damage organic materials such as latex, plastic and animal lung tissue.
Ozone is diamagnetic, which means that all of its electrons are in pairs. In contrast, O 2 is paramagnetic, containing two unpaired electrons.
Structure
According to experimental evidence from microwave spectroscopy, ozone is a bent molecule, with symmetry C 2v (similar to water molecules). Distance O - O is 127.2 pm (1.272 ÃÆ'...). The angle of O - O - O is 116.78 Â °. Central atom sp Ã,² in hybridization with one free pair. Ozone is a polar molecule with a dipole moment of 0.53 D. This molecule can be represented as a resonant hybrid with two contributing structures, each with a single bond on one side and a double bond on the other. This setting has an overall bond order of 1.5 for both parties.
Reaction
Ozone is one of the strongest known oxidizers, much stronger than O 2 . It is also unstable at high concentrations, decaying into ordinary diatomic oxygen. Its beak varies with atmospheric conditions such as temperature, humidity and air movement. In a confined space with a fan that drives the gas, ozone has a half-life of about a day at room temperature. Some unverified claims imply that ozone can have half the life as short as half an hour in atmospheric conditions.
- 2 O
3 -> 3 O
2
This reaction takes place faster with increasing temperature. Ozone deflagation may be triggered by sparks, and may occur at 10% by weight or higher ozone concentrations.
Ozone can also be produced electrochemically on an electrochemical cell anode of oxygen. This reaction can be used to create smaller amounts of ozone for research purposes.
O
3 (g) 2H 2e - <-> O
2 (g) H
2 O EÂ ° = 2.075V
This reaction can be observed as an unwanted reaction in a Hoffman gas appliance during electrolysis of water when the voltage is set above the required voltage.
With metal
Ozone oxidizes most metals (except gold, platinum, and iridium) to metal oxides in the highest oxidation state. As an example:
- Cu O
3 -> CuO O
2
With nitrogen and carbon compounds
Ozon juga mengoksidasi oksida nitrat menjadi nitrogen dioksida:
- NO O
3 -> NO
2 O
2
Reaksi ini disertai dengan chemiluminescence. The NO
2 dapat teroksidasi lebih lanjut:
- NO
2 O
3 -> NO
3 O
2
NO
3 dibentuk dapat bereaksi dengan NO
2 untuk form N
2 O
5 .
Solid nitronium perklorat dapat dibuat dari NO 2 , ClO 2 , dan O
3 gas:
- NO
2 ClO
2 2 O
3 -> NO
2 ClO < br> 4 2 O
2
Ozon tidak bereaksi dengan garam ammonium, tetapi mengoksidasi amonia menjadi amonium nitrat:
- 2 NH
3 4 O
3 -> NH
4 NO < span>
3 4 O
2 H < br> 2 O
Ozone reacts with carbon to form carbon dioxide, even at room temperature:
- C 2 O
3 -> CO
2 2 O
2
With sulfur compound
Ozone oxidizes sulfides to sulfates. For example, lead (II) sulfide is oxidized into lead (II) sulfate:
- PbS 4 O 3 -> PbSO 4 4 O 2
Sulfuric acid can be produced from ozone, water and elemental sulfur or sulfur dioxide: 2 -> H 2 SO 4
In the gas phase, the ozone reacts with hydrogen sulfide to form sulfur dioxide:
- H 2 S O 3 -> SO 2 H 2 O
In aqueous solutions, however, two competing simultaneous reactions occur, one to produce sulfur elements, and one to produce sulfuric acid:
- H 2 -> S O 2 H 2 O
- 3 H 2 -> 3 H 2 SO 4
With alkenes and alkenes
Alken can be oxidatively cleaved by ozone, in a process called ozonolysis, giving alcohols, aldehydes, ketones, and carboxylic acids, depending on the second step of the examination.
Ozone can also break down the alkalo to form anhydride or concreted acid product. If the reaction is carried out in the presence of water, the anhydride is hydrolyzed to produce two carboxylic acids.
Ozonolysis is usually performed in dichloromethane solution, at -78 o C. After the sequence of cleavage and rearrangement, organic ozonides are formed. With reductive work (eg zinc in acetic acid or dimethyl sulphide), ketones and aldehydes will be formed, with oxidative work (eg aqueous hydrogen peroxide or alcohol), carboxylic acids will be formed.
Other substrate
The three ozone atoms can also react, as in the reaction of tin (II) chloride with hydrochloric acid and ozone:
- 3 SnCl 2 6 HCl O
3 -> 3 SnCl 4 3 H 2 O
Perklorate iodine can be made by treating iodine dissolved in cold anhydrous acids with ozone: 4 4 O 3 sub> 3 3 H 2 O
Burning
Ozone can be used for flammable combustion and combustion gases; ozone provides a higher temperature than dioxigenic burning (O 2 ). The following is a reaction to combustion of carbon subnitrides that can also cause higher temperatures:
- 3 C
4
2
3 span>
2
Ozone can react at cryogenic temperatures. At 77Ã,K (-196.22, Â ° C; -321,1Ã, Â ° F), the hydrogen atom reacts with liquid ozone to form a hydrogen superoxide radical, which dimerizes:
- H O
3 -> HO 2 O - 2 HO 2 -> H
2 O
4
Reduction to ozonides
Ozone reduction provides anion ozonide, O -
3 . The derivatives of these anions are explosive and should be stored at cryogenic temperatures. Ozone for all alkali metals is known. KO 3 , RbO 3 , and CsO 3 can be prepared from their respective superoxides:
- KO 2 O 3 -> KO 3 O 2
Although KO 3 can be formed as above, it can also be formed from potassium hydroxide and ozone:
- 2 KOH 5 O 3 -> 2 KO 3 5 O 2 H 2 O
NaO 3 and LiO 3 should be prepared by CsO 3 in NH 3 or Li : 3 Na -> Cs NaO 3
Calcium solution in ammonia reacts with ozone to be administered to ammonium ozonide instead of calcium ozonide:
- 3 Ca 10 NH 3 6 O
3 -> CaÃ, Â · 6NH 3 Ca (OH) 2 Ca (NOT 3 ) 2 2 NH 4 O 3 2 O 2 H 2
Apps
Ozone can be used to remove iron and manganese from water, forming a filterable precipitate:
- 2 Fe 2 O 3 5 H 2 O -> 2 Fe (OH) 3 (s) O 2 4 H
- 2 Mn 2 2 O 3 4 H 2 O -> 2 MnO (OH) 2 ( s) 2 O 2 4 H
Ozone will also oxidize the dissolved hydrogen sulfide in water to sulfuric acid:
- 3 O
3 H 2 S -> H 2 SO 3 3 O 2
These three reactions are very important in the use of ozone well water treatment.
Ozone will also detoxify cyanide by turning it into a cyanate.
- CN - O 3 -> CNO - O 2
Ozone will also completely decompose urea:
- ( 2 ) 2 CO O 3 -> N 2 CO 2 2 H 2 O
Properties of spectroscopy
Ozone is a bent triathomic molecule with three vibration modes: symmetric stretching (1103,157 cm -1 ), bends (701,42 cm -1 ) and stretching antisymmetric (1042,096 cm -1 ). Symmetrical stretching and twists are weak dampers, but a strong antisymmetric stretch and are responsible for ozone being an important minor greenhouse gas. The IR band is also used to detect ambient and atmospheric ozone although UV-based measurements are more common.
The electronic spectrum of ozone is quite complex. The description can be seen in MPI Mainz UV/VIS Spectral Atlas ofGaseous Molecules of Atmospheric Interest.
All bands are dissociative, which means that the separate molecules become O O 2 after absorbing the photons. The most important absorption is the Hartley ribbon, extending from slightly above 300 m down to slightly above 200 m. This band is responsible for absorbing UV C in the stratosphere.
On the high wavelength side, Hartley's band transitions into what is called the Huggins band, which falls rapidly until it disappears ~ 360 nm. Above 400 m, stretching deep into the NIR, is the Chappius and Wulf bands. There, unstructured absorption bands are useful for detecting high ambient ozone concentrations, but are so weak that they do not have much of a practical effect.
There is an additional absorption band in the distant UV, which rises slowly from 200 nm to a maximum of ~ 120 nm.
Ozone in Earth's atmosphere
The standard way to express total ozone levels (the amount of ozone in a particular vertical column) in the atmosphere is to use the Dobson unit. Point measurements are reported as mole fractions in nmol/mol (parts per billion, ppb) or as in concentrations? G/m 3 . Studies of ozone concentrations in the atmosphere began in the 1920s.
Ozone Layer
Location and production
The highest level of ozone in the atmosphere is in the stratosphere, in an area known as the ozone layer between about 10 km and 50 km above the surface (or between about 6 and 31 miles). However, even in this "layer," the ozone concentration is only two to eight parts per million, so most oxygen is oxygen, O 2 , about 210,000 parts per million volumes.
Ozone in the stratosphere is largely produced from shortwave ultraviolet light between 240 and 160 nm. Oxygen begins to absorb weakly at 240 nm in the Herzberg band, but most of the oxygen is separated by absorption in Schumann-Runge bands between 200 and 160 n where ozone is not absorbed. While shorter wavelengths, extending to the X-Ray boundary, are sufficiently energetic to separate the molecular oxygen, relatively small, and, strong solar emissions in Lyman-alpha, 121 nm, fall at the point where molecular oxygen absorption is minimum.
The process of ozone creation and destruction is called the Chapman cycle and begins with molecular oxygen photolysis
- O
2 photon (radiation? & lt; 240 nm) -> 2 O
followed by the reaction of oxygen atoms with other oxygen molecules to form ozone.
- O O
2 M -> O
3 M
where "M" represents the third body that carries excess energy from the reaction. The ozone molecule can then absorb UV-C photons and dissociate
O
3 -> O O
2 kinetik energi
Excess kinetic energy heats the stratosphere when the O atoms and molecular oxygen fly apart and collide with other molecules. Conversion of UV rays into this kinetic energy heats the stratosphere. The oxygen atoms generated in ozone photolysis then react with other oxygen molecules as in the previous step to form more ozone. In a clear atmosphere, with only nitrogen and oxygen, ozone can react with atomic oxygen to form two molecules of O 2
- O
3 O -> 2 O
2
The approximate level of this termination step for the oxygen cycle of atoms back to ozone can be found simply by taking the ratio from the concentration of O 2 to O 3 . The termination reactions are catalyzed by the presence of certain free radicals, the most important being hydroxyl (OH), nitric oxide (NO) and atomic chlorine (Cl) and bromine (Br). In the second half of the 20th century the amount of ozone in the stratosphere was found to decrease, in large part due to increased concentrations of chlorofluorocarbons (CFC) and chlorinated organic and brominated organic molecules. Concerns over the health effects of the decline led to the Montreal Protocol of 1987, a ban on the production of many ozone depleting chemicals and in the first and second decades of the early 21st century from the restoration of stratospheric ozone concentrations.
The importance of surface life on Earth
Ozone in the ozone layer filters the wavelength of sunlight from about 200 nm of UV rays to 315 nm, with absorption of the ozone peak at about 250 nm. UV absorption of ozone is important for life, therefore expanding UV absorption by ordinary oxygen and nitrogen in the air (which absorbs all wavelengths & lt; 200 nm) through lower UV-C (200-280 nm) and all UV-B band (280-315 nm). The remaining unabsorbed minor part of UV-B after passing ozone causes skin to burn in humans, and direct DNA damage to living tissue in both plants and animals. The effect of ozone on UV-B mid-range light is illustrated by its effect on UV-B at 290nm, which has a radiation intensity of 350 million times stronger in the upper atmosphere as on the surface. However, enough UV-B radiation at the same frequency reaches the ground causes some sunburn, and this same wavelength is also among those responsible for the production of vitamin D in humans.
The ozone layer has little effect on longer UV wavelengths called UV-A (315-400Ã, nm), but this radiation does not cause sunburn or direct DNA damage, and while it may not cause long-term skin damage to humans certain, it is harmless to the plants and health of organisms living on the surface of the earth in general (see ultraviolet for more information on near ultraviolet).
Low level ozone
Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not transmitted directly by car engines or by industrial operations, but is formed by the reaction of sunlight in the air that contains hydrocarbons and nitrogen oxides that react to form ozone directly at pollution sources or many miles under the wind.
Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins removing them from the air, but the product itself is a major component of the smog. Ozone photovolysis by UV rays causes the production of hydroxyl radicals HOo and this plays a part in the removal of hydrocarbons from the air, but is also the first step in the manufacture of smoke haze components such as peroxyacyl nitrate, which can be a strong eye. irritation. The life span of tropospheric ozone atmosphere is about 22 days; the main removal mechanism is deposited onto the soil, the above mentioned reactions give HOo, and by reaction with OH and the peroxy radical HO 2 o.
There is evidence of significant decline in agricultural yields due to increased ground level ozone and pollution that interfere with photosynthesis and inhibit the overall growth of some plant species. The US Environmental Protection Agency proposes a secondary regulation to reduce crop damage, in addition to key regulations designed to protect human health.
Examples of specific cities with high ozone readings are Houston, Texas, and Mexico City, Mexico. Houston has a reading of about 41 nmol/mol, while Mexico City is much more dangerous, with readings of about 125 nmol/mol.
Ozone crack
Ozone gas attacks any polymer having olefin or double bonds in the chain structure, such as natural rubber, nitrile rubber, and styrene- butadiene rubber. Products made using this polymer are very susceptible to attack, which causes cracks to grow longer and deeper over time, the rate of crack growth depends on the load carried by the rubber component and the ozone concentration in the atmosphere. Such materials can be protected by adding antiozonants, such as waxes, which bind the surface to create protective films or blend into the material and provide long-term protection. Ozone cracking is usually a serious problem with car tires, but the problem is now only seen on very old tires. On the other hand, many important products, such as gaskets and O-rings, can be attacked by ozone produced in compressed air systems. Fuel lines made of reinforced rubber are also susceptible to attack, especially inside the engine compartment, where some ozone is generated by electrical components. Storing rubber products near DC electric motors can accelerate ozone cracking. The motor commutator produces sparks which in turn produce ozone.
Ozone as a greenhouse gas
Although ozone is present in the soil surface before the Industrial Revolution, peak concentrations are now much higher than pre-industrial levels, and even the background concentrations far from sources of pollution are much higher. Ozone acts as a greenhouse gas, absorbing some of the infrared energy emitted by the earth. Measuring the potential of greenhouse gases from ozone is difficult because it does not exist in uniform concentration around the world. However, the most widely accepted scientific assessment related to climate change (eg, the Intergovernmental Panel on Third Changes of Climate Change Reports) shows that coercion of tropospheric ozone radiation is about 25% of carbon dioxide.
The annual global warming potential of tropospheric ozone is between 918-1022 tons of carbon dioxide/tons of tropospheric ozone equivalent. This means on a per-molecular basis, the ozone in the troposphere has the effect of forcing radiation about 1,000 times stronger than carbon dioxide. However, tropospheric ozone is a short-lived greenhouse gas, which decays in the atmosphere much faster than carbon dioxide. This means that over the span of 20 years, the global warming potential of tropospheric ozone is much less, about 62-69 tons of carbon dioxide/tons of tropospheric ozone equivalent.
Because of its short-lived nature, tropospheric ozone does not have a strong global effect, but has the effect of forcing very strong radiation on a regional scale. In fact, there are areas in the world where tropospheric ozone has radiative forcing up to 150% of carbon dioxide.
Health effects
Ozone air pollution
Ozone precursors are a group of pollutants, especially those emitted during burning fossil fuels. Earth-level ozone pollution (tropospheric ozone) is made near the surface of the Earth by daylight UV rays on these precursors. Earth-level ozone is primarily derived from fossil fuels precursors, but methane is a natural precursor, and the natural level of very low ozone surface at the soil surface is considered safe. This section examines the health effects of burning fossil fuels, which increases the ozone level above the background level.
There is ample evidence to suggest that ozone at ground level can harm lung function and irritate the respiratory system. Exposure to ozone (and the pollutants that produce it) is associated with premature death, asthma, bronchitis, heart attacks, and other cardiopulmonary problems.
Long-term exposure to ozone has been shown to increase the risk of death from respiratory diseases. A study of 450,000 people living in US cities saw a significant correlation between ozone levels and respiratory diseases during 18 years of follow-up. The study revealed that people living in cities with high ozone levels, such as Houston or Los Angeles, had more than a 30% increased risk of death from lung disease.
Air quality guidelines such as those from the World Health Organization, the United States Environmental Protection Agency (EPA) and the European Union are based on detailed studies designed to identify levels that can cause measurable health effects.
According to scientists with the US EPA, vulnerable people can be affected by ozone levels as low as 40 nmol/mol. In EU, the current target value for ozone concentration is 120 Âμg/m 3 which is about 60 nmol/mol. This target applies to all Member States in accordance with Directive 2008/50/EC. The concentration of ozone is measured as an average daily average maximum of 8 hours and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. While the directives require in the future strict compliance with 120 Âμg/m 3 limit (ie the average ozone concentration is not exceeded on any given day of the year), no date is set for this requirement and this is treated as a long-term goal.
In the US, the Clean Air Act directs the EPA to set National Air Quality Standards for some pollutants, including ground-level ozone, and countries that do not meet these standards should take steps to reduce their level. In May 2008, under a court order, the EPA lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. This move proved controversial, as the scientists and advisory boards of the agency itself have recommended to lower the standard to 60 nmol/mol. Many public health and environmental groups also support the standard 60 nmol/mol, and the World Health Organization recommends 51 nmol/mol.
On January 7, 2010, the US Environmental Protection Agency (EPA) announced a revision filed with the National Air Quality Standard (NAAQS) for pollutant ozone, a major component of smog:
- ... EPA suggests that the primary standard rate of 8 hours, set at 0.075? mol/mol in the final rule of 2008, should be set to a lower level in the range of 0.060 to 0.070? mol/mol, to provide better protection for children and other '' at risk 'populations of the O
3 - related adverse health effects that range from decreased lung function and increased respiratory symptoms for serious indicators of respiratory morbidity including visits to the emergency department and home acceptable pain for respiratory causes, and possibly cardiovascular-related morbidity as well as total non-accidental and cardiopulmonary deaths.
On October 26, 2015, the EPA issued a final rule with the effective date of December 28, 2015 which revised the main NAAQS 8 hours from 0.075 ppm to 0.070 ppm.
The EPA has developed an Air Quality Index (AQI) to help explain air pollution levels to the general public. Below the current standard, the average ozone mole fraction of eight hours from 85 to 104 nmol/mol is described as "unhealthy for the sensitive group", 105 nmol/mol to 124 nmol/mol as "unhealthy", and 125 nmol/mole to 404 nmol/mol as "very unhealthy".
Ozone can also be present in indoor air pollution, in part as a result of electronic equipment such as photocopiers. Connections have also been known to exist among increased pollen, mold spores, and ozone caused by storms and hospital admission with asthma.
In the Victorian era, one of the British people's myths claimed that odor was caused by ozone. In fact, the characteristic "odor of the sea" is caused by dimethyl sulfide, a chemical produced by phytoplankton. The Victorian English people are considered the odor produced "corroborating".
Heat wave
Ozone production increases during heat waves, because plants absorb less ozone. It is estimated that ozone uptake is limited by the plants responsible for the loss of 460 lives in the UK in the summer of 2006. Similar investigations to assess the combined effects of ozone and heat during the European heat wave in 2003, concluded that apparently additive.
Physiology
Ozone, along with reactive oxygen forms such as superoxide, singlet oxygen, hydrogen peroxide, and hypochlorite ions, are naturally produced by white blood cells and other biological systems (such as marigold roots) as a means to destroy foreign bodies. Ozone reacts directly with organic double bonds. Also, when ozone decomposes into dioxygen, it generates oxygen-free radicals, which are highly reactive and capable of damaging many organic molecules. In addition, it is believed that the strong oxidizing properties of ozone can be a contributing factor to inflammation. The causal relationship of how ozone is made in the body and what it does is still under consideration and is still subject to various interpretations, because other bodily chemical processes can trigger some of the same reactions. A team led by Paul Wentworth Jr. from the Department of Chemistry at the Scripps Research Institute have shown evidence linking an antibody-catalyzed water oxidation pathway from the human immune response to ozone production. In this system, ozone is produced by the production of trioxidane catalyzed by antibodies from water and singlet oxygen produced by neutrophils.
When inhaled, ozone reacts with compounds lining the lungs to form specific metabolites derived from cholesterol that are thought to facilitate the buildup and pathogenesis of atherosclerotic plaques (a form of heart disease). This metabolite has been confirmed as naturally occurring in the human atherosclerotic artery and categorized into a class of sekosterol called atheronals , produced by cholesterol double-ozonolysis double bond to form 5.6 secosterol as well as secondary condensation. products through aldolization.
Ozone has had adverse effects on plant growth: "... ozone reduces total chlorophyll, carotenoids and carbohydrate concentrations, and increases in 1-aminocyclopropane-1-carboxylic content (ACC) and ethylene production." In treated plants, ascorbic leaf ponds decrease , while lipid peroxidation and soluble leakage were significantly higher than in ozone-free controls.The data suggest that ozone triggers a protective mechanism against oxidative stress in citrus. "
Security rules
Due to the highly oxidizing nature of ozone, ozone is a primary irritant, which primarily affects the eyes and respiratory system and can be harmful at low concentrations. Canada Occupational Health and Safety Center reports that:
"Even very low ozone concentrations can be harmful to the upper respiratory tract and lungs.The severity of the injury depends on both by the concentration of ozone and the duration of exposure.Small and permanent lung injury or death can result from even very short term exposure on relatively low concentrations. "
To protect workers potentially exposed to ozone, the US Occupational Safety and Health Administration has set a permitted 0.1 (PEL) exposure limits? Mol/mol (29 CFR 1910.1000 table Z-1), calculated as a weighted average of 8 hours of time. Higher concentrations are very dangerous and NIOSH has set a Life and Health Limit (IDLH) of 5? Mol/mol. The work environment in which ozone is used or where it is possible to be produced should have adequate ventilation and it is wise to have a monitor for ozone that will alarm if the concentration exceeds OSHA PEL. Continuous monitoring of ozone is available from several suppliers.
Increased ozone exposure may occur on passenger planes, with levels dependent on altitudes and atmospheric turbulence. The Federal Aviation Authority Regulations of the United States set a limit of 250 nmol/mol with an average maximum of four hours 100 nmol/mol. Some aircraft are equipped with ozone converters in the ventilation system to reduce passenger exposure.
Production
Ozone generators are used to produce ozone to clean air or remove the smell of smoke in uninhabited rooms. This ozone generator can produce more than 3 g ozone per hour. Ozone is often formed in nature under conditions where O 2 will not react. Ozone used in industry is measured in? Mol/mol (ppm, parts per million), nmol/mol (ppb, parts per billion) ,? G/m 3 , mg/h (milligrams per hour) or percent weight. The concentration regimens applied range from 1% to 5% (in the air) and from 6% to 14% (in oxygen) to older generation methods. The new electrolytic method can reach 20% to 30% of the concentration of ozone dissolved in the output water.
Temperature and moisture play a big role in how much ozone is produced using traditional generation methods (such as corona release and ultraviolet light). The old generation method will produce less than 50% of nominal capacity if operated with damp ambient air, compared to very dry air. The new generator, using electrolytic methods, can achieve higher purity and dissolution through the use of water molecules as a source of ozone production.
Corona discharge method
This is the most common type of ozone generator for most industrial and personal uses. While variations in the ozone coronal release method of ozone-producing heat, including medical classes and industrial grade ozone generators, these units typically work with corona release tubes. They are usually cost-effective and do not require an oxygen source other than the surrounding air to produce a 3-6% ozone concentration. Ambient air fluctuations, due to weather or other environmental conditions, cause variability in ozone production. However, they also produce nitrogen oxide as a by-product. The use of air dryers can reduce or eliminate the formation of nitric acid by removing moisture and increasing ozone production. The use of oxygen concentrators can further increase ozone production and further reduce the risk of formation of nitric acid by removing not only water vapor, but also most of the nitrogen.
Ultraviolet light
The UV ozone generator, or ultraviolet vacuum ozone generator (VUV), uses a light source that produces a narrow ultraviolet light, the part produced by the Sun. UV The sun supports the ozone layer in the Earth's stratosphere.
UV ozone generators use ambient air for ozone production, no air preparation system is used (air dryers or oxygen concentrators), therefore these generators tend to be less expensive. But UV ozone generators typically produce ozone with concentrations of about 0.5% or lower that limit the production rate of potential ozone. Another disadvantage of this method is that it requires ambient air (oxygen) to be exposed to UV sources for longer periods, and any gas that is not exposed to UV sources will not be treated. This makes UV generators impractical for use in situations related to airflow or rapid water flow (in-duct air sterilization, for example). Ozone production is one of the potential dangers of ultraviolet germ radiation. The VUV ozone generator is used in pool and spa applications ranging from millions of gallons of water. The VUV ozone generator, unlike corona release generators, does not produce harmful nitrogen byproducts and unlike corona discharge systems, the VUV ozone generator works very well in humid air environments. There is usually no need for expensive off-gas mechanisms, and no air dryers or oxygen concentrators require additional costs and maintenance.
Cold Plasma
In the cold plasma method, pure oxygen gas is exposed to the plasma created by dielectric dissolution. Diatomic oxygen is divided into single atoms, which are then rejoined in triplets to form ozone.
The cold plasma machine uses pure oxygen as the input source and generates a maximum concentration of about 5% ozone. They produce ozone in much larger quantities in a given time space compared to ultraviolet production. However, since cold plasma ozone generators are very expensive, they are found less frequently than the previous two types.
The output manifests as the transfer of the electron filament (micro discharge) in the gap between the two electrodes. To evenly distribute micro emissions, a dielectric insulator should be used to separate metal electrodes and to prevent arcing.
Some cold plasma units also have the ability to produce short-term allotrope oxygen which includes O 4 , O 5 , O 6 , O 7 , etc. This species is even more reactive than O
3 .
Electrolytes
The generation of ozone electrolyte (EOG) divides the water molecules into H 2 , O 2 , and O 3 . In most EOG methods, hydrogen gas is removed to leave oxygen and ozone as the only reaction product. Therefore, the EOG can achieve higher dissolution in water without any other competing gas found in corona release methods, such as nitrogen gas present in the ambient air. This generation method can reach 20-30% concentration and does not depend on air quality because water is used as the source material. The production of ozone by electrolysis is usually unfavorable because of the high overpotential required to produce ozone compared with oxygen. This is why ozone is not produced during typical water electrolysis. However, it is possible to increase oxygen overpotential by careful selection of catalysts such as ozone that are preferably produced under electrolysis. The catalysts typically chosen for this approach are lead or dioxide boron-doped diamond.
Special considerations
Ozone can not be stored and transported like other industrial gases (because it rapidly decays into diatomic oxygen) and therefore must be produced on site. The available ozone generators vary in the setting and design of high voltage electrodes. At a production capacity higher than 20 kg per hour, the gas/water cylinder heat exchanger can be used as a ground electrode and assembled with a tubular high-voltage electrode on the gas side. The typical gas pressure regime is about 2 bar (200 kPa) absolute in oxygen and 3 bars (300 kPa) absolute in the air. Several megawatts of electrical power can be installed in large facilities, applied as a single phase AC current at 50 to 8000 Hz and a peak voltage between 3,000 and 20,000 volts. The applied voltage is usually inversely proportional to the applied frequency.
The dominant parameter affecting the efficiency of ozone generation is the gas temperature, which is controlled by cooling water temperature and/or gas speed. The cooler the water, the better the ozone synthesis. The lower the gas speed, the higher the concentration (but the lower the net ozone it generates). Under typical industrial conditions, nearly 90% of the effective power is dissipated as heat and must be removed with sufficient cooling water flow.
Due to the high reactivity of ozone, only some materials can be used such as stainless steels (quality 316L), titanium, aluminum (for no moisture), glass, polytetrafluorethylene, or polyvinylidene fluoride. Viton can be used with a constant mechanical force restriction and absence of moisture (the restriction of moisture applies depending on the formulation). Hypalon can be used with the restriction that no water is in contact with it, except for normal atmospheric levels. Embrittlement or shrinkage is a common mode of elastomer failure with ozone exposure. Ozone rift is a common mode of failure of elastomeric seals such as O-rings.
Silicone rubbers are usually sufficient to be used as gaskets in ozone concentrations below 1 wt%, as in equipment to accelerate aging of rubber samples.
Incidental production
Ozone can be formed from O
2 by the release of electricity and by the action of high-energy electromagnetic radiation. Unexpressed spikes in electrical contacts, motor brushes, or mechanical switches break the chemical bonds of atmospheric oxygen surrounding the contact O
2 -> 2O]. Oxygen free radicals in and around the arc recombine to create ozone [ O
3 ]. Certain electrical appliances produce significant ozone levels. This is especially true for high voltage devices, such as ionic air purifiers, laser printers, photocopiers, tasers and arc welders. Electric motors using brushes can produce ozone from repeated sparks inside the unit. Large brush-using motors, such as those used by elevators or hydraulic pumps, will produce more ozone than smaller motors.
Ozone is also formed in the Catatumbo lightning storm phenomenon on the Catatumbo River in Venezuela, although ozone instability makes it doubtful that it has an effect on ozonosphere. It is the largest natural ozone generator in the world, the call borrowing for it is designated as a UNESCO World Heritage Site.
Production lab
In the laboratory, ozone can be produced by electrolysis using a 9 volt battery, graphite pencil rod cathode, platinum wire anode and 3 molar electrolytic sulfuric acid. Half-cell reactions are:
- 3 H 2 O -> O 3 6 H 6 e - (? E o = -1.53 ​​V)
- 6 H 6 e - -> 3 H 2 (? E o = 0 V) ​​
- 2 H 2 4 H 4 e - (? E o = 1.23 V)
In a clean reaction, three water equivalents are converted to one ozone equivalent and three equivalents of hydrogen. The formation of oxygen is a competitive reaction.
It can also be generated by a high voltage arc. In its simplest form, high-voltage AC, such as the output of the Neon-Sign transformer is connected to two metal rods with the ends placed close enough to each other to allow the arc. The resulting arc will convert atmospheric oxygen into ozone.
It is often desirable to contain ozone. This can be done with an apparatus consisting of two concentric glass tubes sealed together at the top with a gas port at the top and bottom of the outer tube. The inner core must have a metal sheet inserted into it that is connected to one side of the power source. The other side of the power source should be connected to another sheet of foil wrapped around the outer tube. Dry source O
2 applied to bottom port. When high voltage is applied to the lead foil, electricity will flow between the dry dioxide in the middle and form the O
3 and O
2 that will flow out of the top port. The reactions can be summarized as follows:
- 3 O
2 - power -> 2 O
3
Applications
Industry
The largest use of ozone is in the preparation of drugs, synthetic lubricants, and many other commercially useful organic compounds, where it is used to break carbon-carbon bonds. It can also be used for bleaching agents and to kill microorganisms in air and water sources. Many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine. Ozone has a very high oxidation potential. Ozone does not form organochlorine compounds, nor does it remain in the water after treatment. Ozone may form suspected carcinogen bromates in source water with high bromide concentrations. The US Safe Drinking Water Act mandates that this system introduces a certain amount of chlorine to maintain a minimum of 0.2? Mol/mol residual chlorine free in the pipe, based on the results of routine testing. Where power is abundant, ozone is a cost-effective method for water treatment, as it is produced on demand and does not require the transportation and storage of hazardous chemicals. After decaying, do not leave a taste or smell in drinking water.
Although low ozone levels have been advertised as the use of disinfectants in residential homes, the concentrations of ozone in dry air are required to have a substantial rapid effect on airborne pathogens exceeding the safe levels recommended by the US Occupational Safety and Health Administration of the US Environmental Protection Agency. The moisture control can greatly increase the killing power of the ozone and the rate at which it decays back into oxygen (more moisture allows more effectively). The spores of most pathogens are highly tolerant of atmospheric ozone in concentrations where asthma patients begin to experience problems.
Industrially, ozone is used for:
- Disinfecting laundry in hospitals, food factories, nursing homes etc.;
- Disinfect water in chlorine place
- Eliminates the smell of air and objects, such as after a fire. This process is widely used in fabric restoration
- Kill bacteria on food or on the contact surface;
- Clean pool and spa
- Kill insects in stored items
- Scrub the yeast and airborne spores from the air at the food processing plant;
- Wash fresh fruits and vegetables to kill yeast, fungi, and bacteria;
- Chemically attack contaminants in water (iron, arsenic, hydrogen sulfide, nitrite, and organic complexes incorporated as "colors");
- Provide relief for flocculation (molecular agglomeration, which aids in filtration, in which iron and arsenic are removed);
- Producing chemical compounds through chemical synthesis
- Clean fabrics and bleach (formerly used in fabric restoration, patent last use);
- Act as antichlor in chlorine-based bleaching;
- Help in plastic processing to enable adhesion of ink;
- The age of the rubber sample to determine the life of a rubber batch;
- Eradicate parasites containing water such as Giardia lamblia and Cryptosporidium in surface water treatment plants.
Ozone is a reagent in many organic reactions in laboratory and in industry. Ozonolysis is the division of alkene compounds into carbonyls.
Many hospitals around the world use large ozone generators to decontaminate operating rooms between operations. The rooms are cleaned and then sealed airtight before being filled with ozone that effectively kills or neutralizes all the remaining bacteria.
Ozone is used as an alternative to chlorine or chlorine dioxide in bleaching wood pulp. It is often used in conjunction with oxygen and hydrogen peroxide to eliminate the need for chlorine-containing compounds in the manufacture of high quality white paper.
Ozone can be used to detoxify cyanide waste (eg from gold and silver mining) by oxidizing cyanides to cyanates and eventually into carbon dioxide.
Consumer
Devices that produce high levels of ozone, some of which use ionization, are used to clean and remove the smell of unoccupied buildings, rooms, requiring ducts, wood, boats and other vehicles.
In the US, low ozone-depleting air cleaners have been sold. This type of air purifier is sometimes claimed to mimic the natural way of purifying unfiltered air and to clean the surface and the household. The United States Environmental Protection Agency (EPA) has stated that there is "evidence to show that at concentrations not exceeding public health standards, ozone is ineffective at removing many odor-causing chemicals" or "viruses, bacteria, fungi, or" other biological pollutants " Furthermore, his report states that "the results of some controlled studies show that ozone concentrations are much higher than this [human safety] standard is possible even when a user follows the manufacturer's operating instructions".
Ozone water is used for washing clothes and for cleaning food, drinking water, and surfaces at home. According to the US Food and Drug Administration (FDA), it is "changing the food additive regulations to provide safe use of ozone in the gas and water phase as an antimicrobial agent in foods, including meat and poultry." Studies at California Polytechnic University show that 0.3? Mol/mol ozone level dissolved in the filtered tapwater can result in a reduction of more than 99.99% in food-borne microorganisms such as salmonella, E. coli 0157: H7 and Campylobacter . This quantity is 20,000 times the WHO recommended limit stated above. Ozone can be used to remove pesticide residues from fruits and vegetables.
Ozone is used in homes and hot tubs to kill bacteria in the water and to reduce the amount of chlorine or bromine needed by reactivating them to their free state. Because ozone is not in the water long enough, ozon itself is not effective to prevent cross contamination between baths and should be used in conjunction with halogens. Ga
Source of the article : Wikipedia
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