Fluorine is the most active element and can interact with almost any other element at room temperature. Even gold can burn in fluorine gas after heating, and it can also burn in fluorine gas after heating in nature. There is no monomer fluorine in nature. Fluorine gas is light yellow, which is very irritating and cultural. Fluorine pollution in industry mainly occurs in the form of hydrogen fluoride and other fluorides. Fluorine is widely distributed in nature, accounting for about two-tenths of the total land cover. The heaviest fluorine minerals are fluorite (calcium fluoride, CaF2) and cryolite (na3a1a6). The fluorine content of apatite is about 3%[ calcium fluorophosphate, Ca5F(PO4)3, (for example, the average content of apatite in Morocco is 42% of phosphorus pentoxide and 3.7% of fluorine)], and the fluorine content of clay is about 0.02-10.50 billion tons, which is the largest amount of toxic gas and the focus of air pollution prevention and control. Density 2.3, colorless, non-flammable, with strong irritating suffocation. It can be liquefied into colorless liquid by adding four atmospheres at room temperature. 57% of sulfur dioxide in the environment exists in nature, but it will not cause pollution because of its dispersion and low concentration, and 43% comes from human factors such as industrial production, which will cause air pollution because of its concentrated source and high concentration. Among the anthropogenic carbon dioxide emissions, coal combustion accounts for 70%, heavy oil combustion accounts for 16%, metallurgical industry accounts for 1 1%, and oil refining industry accounts for 4%. In cities, industrial and domestic coal is the main source of sulfur dioxide. After the sulfur dioxide is discharged from the high chimney, more than 50% of it exceeds 700km after 24 hours under the influence of the high-altitude wind of 1.5km, and it can spread to100 km after 60 hours. After sulfur dioxide enters the atmosphere, if the atmosphere is dry and clean, it can stay for 1 ~ 2 weeks; If the air is polluted or wet, it will be converted into sulfur trioxide and fall to the ground. When sulfur dioxide stays in the atmosphere.

sulphur dioxide

Strong irritation to eyes, nose, throat and respiratory tract; Harmful to liver, kidney and heart. Can reduce the sense of smell and taste, leading to atrophic rhinitis, chronic bronchitis, conjunctivitis and gastritis. Acute poisoning can lead to laryngeal edema, pulmonary edema and even suffocation. Sulfur dioxide is often harmful to the environment with dust and water vapor. The Donora incident in the United States, the smog incident in London, England, and the four-day incident in Japan are all inseparable from sulfur dioxide. For people who are particularly sensitive, the concentration of sulfur dioxide in the air can be detected when it reaches 4 mg/L. Even if the concentration of sulfur dioxide is one in ten thousand, it has obvious effects on cotton, wheat and barley.

The prevention and control measures of sulfur dioxide include: 1, the low sulfur of urban domestic and industrial fuels, and the gradual promotion of low sulfur coal, oil and gas, natural gas and even electricity as energy sources when conditions permit. 2. Fuel desulfurization. Such as strengthening coal washing and coal liquefaction. 3. Flue gas desulfurization. For example, washing flue gas with lime or limestone; Lime or dolomite mixed with coal is used as boiler fuel. 4, high chimney emissions. 5. Transform technology and make comprehensive use of it. For example, sulfuric acid plants use two-to-two absorption instead of one-to-one absorption; Recovery of high concentration sulfur dioxide from tail gas of nonferrous metallurgy to produce sulfuric acid. Wait a minute.

chrome

Chromium is a silvery white luster metal, which is non-toxic and chemically stable. Stainless steel contains more than 12% chromium. Common chromium compounds include hexavalent chromic anhydride, potassium dichromate, sodium dichromate, potassium chromate and sodium chromate. Trivalent chromium trioxide (chromium green, Cr2O3); Bivalent chromium oxide. Among chromium compounds, hexavalent chromium is the most toxic, followed by trivalent chromium. According to research, chromium is a trace element necessary for the life and health of mammals. Lack of chromium can lead to atherosclerosis. Adults need 500-700 micrograms of chromium every day, but the general diet can only provide 50- 100 micrograms. Brown sugar, whole grain brown rice, unrefined oil, millet, carrot and pea have higher chromium content. Chromium can stimulate plant growth, and trace chromium can increase plant yield; However, a slightly higher concentration will inhibit the nitrification of organic matter in soil. Chromic acid, dichromate and its salts can irritate and burn human sticky mold and skin, and lead to injury and contact dermatitis. These compounds enter the human body in the form of steam or dust, which will lead to perforation of nasal septum, gastrointestinal diseases, leukopenia and lung diseases like asthma. Skin contact with chromium compounds can lead to "chrome sores", which heal very slowly. When the concentration of chromic anhydride in the air reaches 0. 15 ~ 0.3 1mg/m3, the nasal septum can be perforated. Trivalent chromium is also a protein coagulant. Some people think that hexavalent chromium can induce lung cancer. In addition, hexavalent chromium, especially chromic acid, has a strong cultivation effect on metal pipes in sewage system, and sodium dichromate with a concentration of 2.3 1 mg/L can corrode pipes. Irrigation with trivalent chromium wastewater containing 3.4- 17.3mg/l can poison all plants.

Chromium pollution is mainly caused by industry. Chromium compounds will be discharged from mining, smelting, manufacturing chromium salts, electroplating, metalworking, tanning, painting, pigment and printing and dyeing industries. For example, in the tanning industry, it is generally necessary to mail 50-60 tons of wastewater containing chromium 4 10mg/l to treat one ton of hides. If ten tons of hides are treated every day, 72-86 tons of chromium will be discharged every year.

The prevention and control of chromium pollution should be considered from the aspects of process reform and comprehensive utilization, such as electroplating and chromium fog recovery of low chromium plating; Using chromium slag to make cast stone, blue brick and chromium lignin; Chromium hydroxide was recovered from chromium plating wastewater and then treated with bright green.

mercury

Mercury, or mercury, is a liquid metal. Specific gravity 13.6, melting point -39.3℃, boiling point 357℃. Mercury can evaporate at room temperature, and its vapor is colorless and tasteless, which is 7 times heavier than air. Mercury and its compounds are very toxic, especially the organic compounds of mercury are more toxic. Fish will be poisoned if they live in water with mercury content of 0.0 1-0.02 mg/L; If people eat 0. 1 g of mercury, they will be poisoned to death. Mercury and its compounds can invade human body through respiratory tract, skin or digestive tract. After entering human body, mercury accumulates in liver, kidney, brain, heart and bone marrow, causing neurotoxicity and deep tissue pathological changes, causing fatigue, dizziness, trembling, gingival bleeding, baldness, paralysis of hands and feet, neurasthenia and other symptoms, even insanity, and then crazy convulsions and death. Organic mercury can also enter the placenta, causing fetal congenital mercury poisoning, or malformation, or dementia. The toxicity of mercury is cumulative, and it usually takes years or longer to react. The food chain has a considerable ability to enrich mercury. For example, the enrichment multiples of freshwater fish and phytoplankton are 1000, freshwater invertebrates are10000, marine plants are1000, and marine animals are 200,000.

Mercury is widely used, such as barometer, manometer, thermometer, mercury vacuum pump, fluorescent lamp, rectifier, mercury-based caustic soda, mercury catalyst, mercuric chloride disinfectant (one thousandth of mercurous chloride is used as disinfectant for surgical instruments), mercuric chloride (mercuric fulminate, explosion initiator), pigments (such as cinnabar, cinnabar, i.e. mercuric sulfide red pigment and inkpad), and pesticides (such as Heineken and Saisai). Mercury pollution also comes from these aspects. When nonferrous metals are smelted, mercury (such as mercury sulfide) in ores will also cause serious mercury pollution. Problems Wastes of catalysts containing mercury (such as mercurous chloride catalyst supported by activated carbon) in organic synthesis industry will also pollute the environment.

Chlorine (Cl2)

Chlorine is a strongly irritating yellow-green gas, which is 2.43 times heavier than air, easily soluble in water (the volume ratio of water to chlorine is 1:2.5) and easily absorbed by activated carbon. Liquefied to liquid chlorine at room temperature and six atmospheric pressures, and its specific gravity is 1.56 times that of water. Chlorine is widely used, mostly for self-disinfection of water, pulp bleaching, bromine production, bleaching powder (calcium hypochlorite), bhc, rubber, ink pigments, grease, polyvinyl chloride, hydrochloric acid, pesticides and so on. Chlorination treatment in metallurgical industry, chlor-alkali industry and so on also has a large amount of chlorine gas emissions. For every ton of liquid chlorine produced, diaphragm electrolysis will emit 9.45 kg of chlorine gas, and mercury electrolysis will emit 65,438+08-72.5 kg of chlorine gas.

The human stomach contains five thousandths of hydrochloric acid, which helps digestion and kills germs. Chlorine is a very active element, which can be directly combined with almost all ordinary metals and nonmetals except carbon, nitrogen and oxygen (it does not react with iron in the absence of water, so liquid chlorine is filled in steel cylinders). Low concentrations of chlorine (hydrogen chloride) in the atmosphere can irritate eyes, nose and throat; Air containing one tenth of chlorine will seriously affect people's health. Inhalation of chlorine can poison respiratory tract and skin mucosa. In mild poisoning, there are burning and oppressive feelings, itchy laryngitis, dyspnea, stinging eyes and tears. High concentration of chlorine (hydrogen chloride) can cause chronic poisoning, leading to rhinitis, bronchitis, emphysema and so on. Some may be allergies, dermatitis, eczema, etc. Chlorine is highly volatile, and water vapor in the air can react with it to generate hydrochloric acid mist and hypochlorous acid, which corrodes articles and harms people, animals and plants everywhere. Therefore, the production and use places of chlorine gas should be strictly managed, and the process equipment should be improved to prevent chlorine gas leakage and comprehensive utilization. For chlorine-containing waste gas, when the concentration exceeds 65438 0%, carbon tetrachloride or sulfur monochloride can be used as absorbent to absorb and concentrate, and then desorb and recover; Chlorine with diluted concentration can be absorbed by water, alkali liquor and iron-containing compounds, but attention should be paid to secondary pollution.

phenol

There are many kinds of phenolic compounds, including phenol, cresol, aminophenol, nitrophenol, naphthol and chlorophenol, among which phenol and cresol are the most prominent. Phenol, also called carbolic acid for short, is slightly acidic (corrosive). It can volatilize at room temperature, giving off a special pungent smell and turning pink in the air. Lysol disinfectant commonly used in hospitals is a dilute solution of sodium phenolate. Cresol, also known as coal phenol, has similar chemical activity and toxicity to phenol and often exists at the same time. According to the number of hydroxyl groups directly connected to the aromatic ring of phenol, phenol can be divided into monohydric phenol and polyhydric phenol. According to its volatility, it can be divided into volatile phenol and nonvolatile phenol. Monophenols are volatile (boiling point below 230℃).

Phenolic compounds are typical poisons and have toxic effects on all living things. Protein can be solidified, so it has a strong bactericidal effect. Its aqueous solution is easy to cause systemic poisoning through the skin; Its vapor is inhaled from the respiratory tract, which is more harmful to the nervous system. Long-term inhalation of phenol vapor or water polluted by phenol can cause chronic cumulative poisoning; Inhalation of high-concentration phenol vapor or splash of phenol liquid or splash of a large amount of phenol liquid on the skin will cause acute poisoning. If not rescued in time, it can lead to nerve center paralysis within three to eight hours. Chronic phenol poisoning usually includes vomiting, diarrhea, loss of appetite, dizziness, anemia and various nervous system diseases. Phenol is toxic to aquatic products, abiotic microorganisms and crops. When the phenol content in water is 0. 1 ~ 0.2 mg/L, the fish will smell and be edible. At 6.5 ~ 9.3 mg/L, it can destroy the gills and pharynx of fish, causing abdominal bleeding, splenomegaly and even death. Direct irrigation of wastewater with phenol concentration higher than 100 mg/L will cause crop death and yield reduction. The lethal oral dose of human p-phenol is 530 mg/kg body weight.

Phenol manufacturing, coking, oil refining, metallurgy, plastics, chemical fiber, insulation materials, phenolic resin, medicine, explosives, pesticides and other industries will have high concentration of phenol-containing wastewater. For example, for every ton of coke produced, 0.2 ~ 0.3 cubic meters of phenol-containing wastewater can be produced.

The ways to solve the phenol-containing wastewater are as follows: first, transform the process to reduce the phenol concentration in wastewater, or recycle water, reduce waste, improve the phenol concentration in wastewater, and facilitate recycling; The second is recycling. The main methods are extraction, adsorption, stripping, ion exchange, chemical precipitation, chemical oxidation, reverse osmosis and biochemical treatment. Generally speaking, for wastewater with phenol concentration above 1000 mg/L, firstly, phenol should be recovered and then destroyed to realize harmless discharge. The concentration of phenol is lower than this concentration,