Source :
http://www.chem-is-try.org/artikel_kimia/kimia_lingkungan/dampak-pencemaran-udara-oleh-belerang-oksida-sox/
Keywords: sulfur oxides, corrosive
Written by Edy Saputra Yoky on 15-10-2009
pollutants-sulfur oxides or belerangGas often written with the Sox made up of gases SO2 and SO3 gases that they both have different qualities. Strong-smelling gas SO2 and non-flammable, whereas SO3 gas is highly reactive. SO3 gas easily reacts with the water vapor in the air to form sulfuric acid or H2SO4. Sulfuric acid is highly reactive, easy to react (to eat) other objects that cause damage, such as perkaratan process (corrosion) and other chemical processes.
Sox have a characteristic strong smell, are corrosive (causes rust), toxic because it is always in the oxygen to reach the stability of gas phasa. Sox cause respiratory system disorders, if the level of 400-500 ppm would be very dangerous, 8-12 ppm cause eye irritation, smelly 3-5 ppm.
SO2 gas concentrations in the air will begin to be detected by human senses (smell the smell) when kensentrasinya ranged from 0.3 to 1 ppm. So in this case is the dominant gas SO2. However, the gas will be met with existing oxygen in the air and then SO3 gas formed through the following reaction:
2SO2 + O2 (air) -> 2SO3
The use of coal as a fuel in some industrial activities such as those in Western European countries and the United States, causing the gas levels in the air increases Sox. The reaction between gases Sox with water vapor in the air to form sulfuric acid and acid sulfite. If the sulfuric acid and acid sulfite down to earth with the fall of rain, there was what is known or denagn Acid Rain acid rain. Acid rain is very harmful because it can damage crops and soil fertility. In some industrialized countries, has a lot of acid rain became a very serious problem because it is damaging. The forest bare by the fall of acid rain will cause more severe environment.
Sox air pollution mainly comes from the use of new coal used in industrial activities, transportation, and so forth. Sulfur in the form of mineral coal iron peritis or FeS2 and can also form metal sulfide minerals such as PBS, HgS, ZnS, CuFeS2 and Cu2S. In the process of iron and steel industry (metal furnace) generated a lot of Sox because the minerals are bound metals in the form of many sulfide. In the process of melting metal sulfide converted into metal oxide. This process also eliminates sulfur and metals because of the sulfur content of the metal impurities. At high temperature metal sulfide easy dioxide into metal oxides through the following reaction:
2ZnS + 3O2 -> 2SO2 + 2ZnO
2PbS + 3O2 -> 2SO2 + 2PbO
Besides depending on the solution used coal as fuel, gas distribution Sox, into the environment also tergnatung drai meteorological conditions and local geography. Air humidity also affects the speed of change in the Sox into sulfuric acid and acid sulfite which will gather together the cloud that would eventually fall as acid rain. Acid rain is causing damage to forests in Europe (especially in Germany) because many industries of iron and steel smelting involving the use of coal or oil in the country.
Sources and exposure patterns
Although natural sources (volcanic or geothermal) may be present in some places, anthropogenic sources, the burning of fossil fuels containing sulfur, dominate the urban areas. These include:
* Source of basic (power plants, factories burning, mining and metal processing)
* Source regions (domestic and district heating)
* Source mobile (diesel engine)
Paparandan duration patterns often show regional differences and a significant season, depending on the dominant source and distribution space, the weather and the spread. At high concentrations, which lasted for several days during winter, the winter months which is stable when the spread is limited, still occurs in many parts of the world where coal is used for the heating. Sources usually dominate the area on several occasions, results in a homogeneous pattern of concentration and exposure / opening.
In contrast, the distance events, a short time from minutes to hours may occur as a result of fumigation, dissemination or direction of the wind from the primary source. The results of exposure patterns vary substantially, depending on the altitude emissions, and weather conditions. Variable while the ambient concentrations are often high in certain circumstances, particularly for local sources.
Impact of Pollution by Sulfur Oxide (Sox)
Most of the gas pollution by sulfur oxides (SOX) comes from burning fossil fuels, especially coal. The presence of water vapor in the air will result in the formation reaction of sulfuric acid and acid sulfite. His reaction is as follows:
SO2 + H2O -> H2SO3
SO3 + H2O -> H2SO4
If the sulfuric acid and acid sulfite is joined in the air condenses and then falls together so that rain water in the form of acid rain pollution can not be avoided anymore. This acid rain can damage crops, with the exception of forest plants. This forest destruction will result in the erosion of fertile soil layers.
Although the concentration of gas dispersed Sox to a low-yield environment, but if the contact time of the plant long enough damage to plants can occur. Concentration of about 0.5 ppm was able to wet the plants, even more so when the concentration of the Sox in the air environment can be seen from the emergence of spots on the leaf surface. If a long exposure time, then it will fall leaves. This will result in decreased plant productivity.
Polluted air has caused human Sox will experience a disruption in pernapasaannya system. This is because the gas is easily Sox became the acid attacks the mucous membranes in the nose, throat and other respiratory tract to the lungs. Sox gas attack that causes irritation of the affected body part.
SO2 layer and the dangers to health
SO2 has a strong influence on the health of acute and chronic. in the form of gas, SO2 can irritate the respiratory system; at high exposure (short time) affects lung function.
SO2 is a by-product H2SO4 affecting the respiratory system. Compounds, consisting of ammonium salts polinuklir or organosulfat, affect the alveoli, and as a soluble chemicals, they passed through the mucus membrane lining of the respiratory system in living organisms.
Particulate aerosols formed by gas to particle formation was found to join with the many health effects.
Globally, the sulfur compounds in a large amount into the atmosphere through human activity around 100 million metric tons of sulfur each year, primarily as a SO2 from burning coal and gas combustion exhaust gases. Large amount of sulfur compounds are also produced by volcanic activity in the form of H2S, the reform process organic materials, and biological sulfate reduction. The amount generated by these biological processes may exceed 1 million metric tons per year H2S.
Some of H2S that reaches the atmosphere quickly changed to SO2 via the reaction:
H2S + 3 / 2 O2 SO2 + H2O
reaction starts from the release of hydrogen ions by hydroxyl radicals,
HO-H2S + HS-+ H2O
which then continued with the following reaction to produce SO2
HS-+ O2 + HO-SO
SO2 + O2 SO + O
Almost half of the sulfur contained in coal in the form pyrit, FeS2, and the other half in the form of organic sulfur. Sulfur dioxide is produced by changes pyrit through the following reaction:
4FeS2 + 11O2 2 Fe2O3 + 8 SO2
Basically, all the sulfur that enters the atmosphere changed in the form of SO2 and only 1% or 2% only as SO2
Although SO2 is produced by human activities is only a small part of the SO2 is diatmosfer, but the effect is very serious because of SO2 can be directly toxic to the surrounding creatures. SO2 is diatmosfer tract irritants pernapasandan increase mucus secretion. People who have weak breathing very sensitive to high SO2 content diatmosfer. With the concentration of 500 ppm, SO2 can cause death in humans.
High enough pollution by SO2 has caused serious havoc. As happened in the valley Nerse Belgium in 1930, SO2 levels reach 38 ppm in the air and cause acute toxicity. During this period caused the death of 60 people and cattle.
Sulfur dioxide is also harmful to plants. The existence of this gas at high concentrations can kill the leaf tissue. edge of the leaf and the area between the bones of damaged leaves. Chronic SO2 causes khlorosis. Iniakan crop damage worsened with the increase of air humidity. SO2 in the air will turn into sulfuric acid. Therefore, the regions with the pollution by SO2 is high enough, the plants will be damaged by sulfuric acid aerosols.
Damage was also experienced by the building materials such as limestone, marble, dolomite will be destroyed by the SO2 from the air. The effect of this damage will appear in his appearance, structural integrity, and age of the building.
John Emsley, University of Cambridge, takes you on a tour of the periodic table: Not just another form of silver, it's pure platinum
Platinum has a variety of different uses. Most of the metal ends up in catalytic convertors for car exhausts, each of which contains less than 2 g but this provides a Pt surface area inside the convertor that is greater than the area of a football pitch. The metal catalyses the complete combustion of unburned hydrocarbons in exhaust fumes into CO2 and water. Platinum's other uses are as cancer medicines, industrial catalysts and in jewellery.
The use of platinum can be traced back to the ancient Egyptians and South Americans. News of the metal first reached Europe in 1726 when José Sánchez de la Torre y Armas, who was the assayer at the royal mint in Bogota, discovered that it was a new metal and not just a form of silver. Alluvial deposits in South America, and especially from the river Pinto, in Columbia, were rich in the metal, which was called platina del Pinto (silver of Pinto) from which platinum got its name.
Setting the standard
Platinum is so stable and resistant to corrosion that it was chosen for the standard kilogram, which is housed at the International Bureau of Weights and Measures, Paris, France. A replica kilogram weight is kept in Russia, which was originally standardised against the one in Paris. When the replica was checked a century later it was found to have decreased in weight by 17 mg (0.0017 per cent). This was probably caused by the loss of traces of osmium in the metal, which had been oxidised to volatile osmium tetroxide.
When platinum deposits were found in the Urals in 1822 it looked as though the metal might be as abundant as silver. The Russian Government even minted 1.5 million rouble coins before the project was abandoned as the price of the metal rose and exceeded the value of the coins. Today more than 70 per cent of the world's platinum comes from South Africa, where it occurs as cooperite (platinum sulfide, PtS). World production of the metal is around 185 tonnes per year.
The versatile metal
© Jupiterimages |
Cisplatin
In 1962, the US chemist Barnett Rosenberg was investigating the effects of electromagnetic fields on cell division using platinum electrodes. He found cells were not dividing normally and he traced this to cis-dichlorodiamminoplatinum(II), PtCl2(NH3)2, cisplatin, which had formed as a result of the chloride and ammonium ions reacting with the electrodes.
Cisplatin was approved as a cancer treatment in 1978 and has been used to treat thousands of patients with testicular, breast, head, and neck cancers, with a cure rate of over 90 per cent. Cisplatin, and similar platinum anticancer drugs, work by bonding strongly to DNA at any point where there are two guanine bases next to each other. The bound complex distorts the DNA, making replication impossible, and the platinum cannot be dislodged by DNA repair enzymes.
Industrial catalysts
Platinum acts as an efficient catalyst. For example, if platinum wire is held in methanol vapour it soon glows red hot as it catalyses the oxidation of methanol to methanal. Platinum can also cause mixtures of oxygen and hydrogen to explode, as if they had been sparked. In the chemical industry fine platinum gauze catalysts are used in the manufacture of nitric acid from ammonia. The production of silicones, benzene and xylenes also use platinum catalysts.
Platinum's success as a catalyst is not its only industrial application. Proton exchange membrane (PEM) fuel cells rely on platinum-coated carbon electrodes. Being a strong metal which resists corrosion, platinum is also used to coat turbine blades in jet engines, in balloon catheters, and pacemakers - where a 90/10 platinum/osmium alloy is used - and in some dental alloys. Like gold, platinum can be hammered into sheets of less than a micron thick and these have been used to coat the cones of space vehicles to protect against intense electromagnetic radiation.
With a growing emphasis on recycling and conserving dwindling natural resources it is important to recover as much platinum as possible to re-use. For example, of the platinum that goes into catalytic convertors, around a quarter is recovered, with the US leading the way in this form of recycling.
Fact file
© Murray Robertson/Visual Elements
Atomic number 78; atomic weight 195.078; melting point 1772ºC; boiling point ca 3800ºC. Platinum is a lustrous, silvery-white, malleable, ductile metal in Group 10 of the Periodic Table. Platinum is unaffected by air and water, but it dissolves in hot concentrated acids such as phosphoric and sulfuric acids, and in molten alkali.
4MnO2 + 4KOH + 2CO2 
