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. If the concentration of phenol is lower than this concentration, it should be treated harmlessly.

cyanide

Cyanides include cyanide, hydrocyanic acid, sodium cyanide, potassium cyanide, ammonium cyanide and nitriles, all of which are highly toxic! Inorganic cyanidation enters and exits in case of acid hydrocyanic acid. Hydrocyanic acid has a specific gravity of 0.687, bitter almond flavor, colorless and transparent liquid, melting point-14℃, boiling point of 25.6℃, and is volatile. Cyanide can cause poisoning when it invades or comes into contact with human body (especially through skin wounds). Mild people have headache, dizziness and difficulty breathing. In severe cases, they will feel dizzy, twitch and their blood pressure will drop. Even they will suddenly faint without warning in two or three minutes, and then die. It is impossible for people cured of cyanide poisoning to have sequelae of nervous system, such as headache, paralysis, aphasia and epilepsy. The lethal dose of hydrocyanic acid to humans is 0.06g, sodium cyanide is 0. 1g, and potassium cyanide is 0. 12g ... Cyanide is harmful to fish. When the cyanide content in water is 0.04 ~ 0. 1ppm, fish can die.

Cyanide-containing wastewater and waste gas mainly come from electroplating, coking, metallurgy, mineral processing, chemical fiber, pharmacy, plexiglass, plastics, gas and other industrial sectors. The main measures to eliminate its harm are: 1, transformation technology. Such as cyanide-free or micro-cyanide electroplating; Cyanide-free mineral processing for mineral processing. 2. Recycling. Such as evaporation concentration, ion exchange and acid volatilization. Wastewater treatment. Mainly include electrolysis, oxidation, dissolution and absorption, biochemical and chemical treatment. , destroying cyanide. For example, liquid chlorine, sodium hypochlorite or bleaching powder are added to waste to convert cyanide into carbon dioxide and nitrogen. Generally, activated sludge aeration tank can be used when cyanide concentration is less than 20mg/L, biological filter can be used when cyanide concentration is 20 ~ 40mg/L, and so on.

cadmium (Cd)

Cadmium is a very toxic heavy metal, and most of its compounds are toxic substances. Cadmium is widely used, such as cadmium salt, cadmium vapor lamp, pigment, smoke bomb, alloy, electroplating, flux, standard battery, metallurgical deoxidizer, neutron rod collector in atomic reactor, etc. For example, the pigment cadmium red consists of cadmium sulfide, cadmium selenide and barium sulfate; Cadmium yellow consists of cadmium sulfide and barium sulfate. Cadmium is very rare in nature and is usually related to lead sulfide, zinc ore, especially sphalerite (ZnS). Mining and smelting of metal ores, electroplating and pigments are the main man-made pollution sources of cadmium. The cadmium content in crude phosphate fertilizer can reach 100 mg/kg, and the cadmium content in calcium superphosphate can reach 50 ~ 170 mg/kg. Cadmium also exists in automobile exhaust. The data show that the cadmium content in soil and grassland on both sides of the road with frequent traffic is significantly higher in the vicinity than in the distance. Tobacco also contains some cadmium.

The "pain" in Japan that shocked the world was caused by cadmium pollution. Mine wastewater containing cadmium pollutes the soil, grain and pasture on both sides of the river, enters the human body through the food chain and slowly accumulates in the kidneys and bones. Will replace the calcium in the bone, so that the bone is severely softened and fractured; Cadmium can cause gastric dysfunction, interfere with the zinc enzyme system in human body and organism, reduce the ratio of zinc to cadmium, and lead to the increase of hypertension. The toxicity of cadmium is potential. Even if the concentration of cadmium in drinking water is as low as 0. 1 mg/L, it can accumulate in human tissues (especially women), and the incubation period can be as long as ten to thirty years, and it is not easy to be detected in the early stage. Data show that the biological half-life of cadmium in human body is 20 ~ 40 years. Cadmium is toxic to human tissues and organs in many ways, which is extremely difficult to treat. Therefore, countries have made very strict regulations on cadmium in industrial "three wastes" discharge. Japan also stipulates that rice with cadmium content exceeding 1 mg/kg is "cadmium rice" and is prohibited from eating. According to the Japanese Environment Agency, the highest normal content of cadmium concentration in rice is 0.3ppm.

Because cadmium compounds have different degrees of toxicity, any method to remove cadmium from wastewater can only change its existence, and any method to remove cadmium from wastewater can only change its existing mode and transfer its existing position, but can not eliminate its toxicity. Therefore, the treatment of cadmium-containing wastewater should be combined with resource utilization as much as possible.

arsenic

Arsenic and its soluble compounds are extremely toxic. For example, arsenic is arsenic trioxide. In nature, it mainly exists in the form of compounds and sometimes in the form of simple substances, including FeAsS, realgar (As2S2) and orpiment (As2S3). Many nonferrous metal ores contain arsenic compounds, so arsenic compounds (such as arsenic trioxide) are discharged during the smelting process of nonferrous metals (such as ore roasting). The average arsenic content in coal can reach 25 mg/kg, so the arsenic concentration in the surrounding air can reach 0.02 μ g/m3 due to the combustion of coal. Arsenic compounds are mostly used to make cemented carbide (such as lead bullets containing 35% arsenic), arsenate drugs, pesticides, rodenticides (usually arsenate and arsenite), decolorants in glass industry, depilators and preservatives in fur industry. Therefore, there are arsenic pollution in metallurgy, sulfuric acid, fertilizer, leather, pesticide and other industries. Problem arsenic can enter the human body through breathing, skin contact and diet. Arsenic can bind to protein and sulfhydryl groups in enzymes, inhibit many biochemical processes in vivo, especially bind to sulfhydryl groups of pyruvate oxidase, inactivate it, and cause serious disorder of cell metabolism. The toxic dose of arsenic is 0.01~ 0.052g, and the lethal dose is 0.06 ~ 0.2g. The acute symptoms of arsenic poisoning are: burning sensation in throat, esophagus and gastrointestinal tract, diarrhea, abdominal pain, headache, nausea, vomiting, oral drinking, cyanosis, rapid drop in blood pressure, and severe cases of rapid death. Arsenic poisoning is also cumulative, which can be accumulated in osteoporosis, kidney, liver, spleen, muscle and keratinized tissues (such as hair, skin and nails). In recent years, it has also been found that the incidence of skin cancer and lung cancer in workers who are often exposed to arsenic-containing substances is higher than that in other industries; Skin ulcer and perforation of nasal septum are common.

Arsenic-containing waste gas should be strictly smoke-eliminated and dust-removed, and recovered in the flue. The treatment method of arsenic-containing waste is generally to add lime, ferrous sulfate and liquid chlorine (or bleaching powder) to precipitate arsenic. The removal efficiency of arsenic in drinking water by various methods is 85% by lime softening method, 70% by charcoal filtration method, 94% by iron sulfide filter bed, 80% by ferric sulfate coagulation method, 98% by ferric chloride coagulation method and 94 ~ 96% by ferric hydroxide precipitation method. If people and animals are poisoned by eating arsenic by mistake, they can take fresh iron hydroxide suspension produced by strong stirring of magnesium oxide and ferrous sulfate solution to detoxify.

smoke and dust

In addition to the dust produced by industrial processes, smoke and dust are mainly the products of fuel combustion. The smoke exhaust of industrial coal is about 3 ~ 18% of the combustion weight, lignite is 1 1%, and anthracite is 8 ~ 9%. For the same ton of coal, the dust produced by residential use is 2 ~ 3 times more than that produced by industrial use. Dust usually contains toxic gases and dust, such as oxides of sulfur, nitrogen and carbon. Dust particles larger than 10 meters will soon settle to the ground, which is called dustfall; Particles smaller than 10 micron are called floating dust, and a considerable part of them are smaller than bacteria, which can float in the atmosphere for hours, even days and years, especially floating dust with a diameter of 0.5 ~ 5 micron, which can not be blocked by human nose hair or excluded by respiratory mucus, but can directly reach alveoli and be carried to the whole body by blood. Some floating dust is accompanied by benzo (a) pyrene or some toxic metal compounds (such as chromium, beryllium and nickel), asbestos and arsenic compounds, which can cause cancer. Half of fine floating dust will attach to lung cells after it enters the human body with the respiratory tract, which is an important cause of respiratory diseases of human beings, animals and plants. Smoke and dust will also weaken sunlight and visibility, absorb the ultraviolet part of sunlight, and increase rickets in children.

The main measures to prevent smoke pollution are: 1, changing fuel composition and combustion mode. Such as using pollution-free or less polluting fuels (natural gas, coal gas, petroleum refinery gas or other energy sources such as sunlight, biogas, wind and tide) instead of coal; Technical transformation of the existing furnace. 2. Regional central heating, large coal-fired power stations are connected in parallel for heating and power supply, and centralized high-efficiency boilers replace decentralized low-efficiency boilers; 3, adopt a variety of smoke and dust removal methods. Wait a minute.

flyash

The ash collected from the chimney of coal-fired boiler is called fly ash. Many thermal power plants discharge fly ash together with the sediment (slag) at the bottom of the boiler, that is, fly ash. China's coal-fired power plants emit nearly 40 million tons of fly ash every year, which is an important pollution source. It not only occupies a lot of land for accumulation, but also often discharges rivers, which makes the river silting worse. The main components of coal ash are silicate, aluminosilicate, silica, sulfate and so on. And the iron content is quite high. It has no hydraulic cementing performance, but after grinding, it can react with chemicals such as lime to form hydraulic cementing materials under the condition of moisture, so fly ash is widely used, mainly for making building materials. Many western countries are opposed to recycling ash resources as a part of national policies. The United States even lists ash as the seventh mineral resource, and 24. 1% (about 65.438+0.64 1 10,000 tons) is sold as a commodity in 65.438+0.978. Recently, China has also formulated the national standard of fly ash cement and listed it as a formal product. Fly ash can also be used as active admixture of cement, admixture of concrete, sintered fly ash ceramsite (artificial aggregate), masonry cement (mortar cement), filler and road building material. The comprehensive utilization of fly ash needs the unified understanding of power, building materials, construction, environmental protection and other departments, and the construction of fly ash utilization industry in China. The pollution and utilization of fly ash can be solved from the development of dust removal technology and dry ash discharge technology in coal-fired power stations to waste recycling, resource productization and product serialization.

Pyrite slag

Also known as cinder, it is produced when pyrite is roasted in the process of producing sulfuric acid. Generally, every 10,000 tons of sulfuric acid can produce about 7,000 tons of pyrite slag. Because there is residual sulfur in coal cinder, drainage will seriously acidify it and corrode bridges and ships.

The iron content of coal cinder is generally 40% ~ 45%, which can be increased to 50% ~ 60% after magnetic separation and gravity separation (desulfurization at the same time). It is a good raw material for ironmaking. About 4000 tons of iron-making raw materials can be selected for every 10,000 tons of pyrite cinder, and the residue can also be used in cement plants. In addition, there are many valuable metals in slag, which should be considered for comprehensive utilization. At present, most of the burning slag in our province has not been treated except for some used in cement plants, which deserves attention.

Steel slag and blast furnace slag

For every ton of pig iron produced, 0.75 tons of blast furnace slag is discharged (it has been reduced to 0.3 tons abroad due to the improvement of high crushing scale and the improvement of ore grade); For every ton of steel produced, 0.25 ton of steel slag is discharged. The chemical composition of blast furnace slag is close to cement, with stable activity, good wear resistance, good hydration and water absorption, mature water quenching process, easy processing and economic recovery. At present, the utilization rate of blast furnace slag in China reaches 60%. However, steel slag is hard, bulky and not easy to be broken, and the water quenching technology is immature and difficult to use. Blast furnace slag is generally used to make slag cement, slag phosphate fertilizer, cast stone, slag fiber, glass-ceramics and so on. The steel slag of alkaline iron smelting furnace (such as Thomas furnace) forms small particles after water quenching, which can be recovered by magnetic separation. The residue is made into phosphate fertilizer and cement (the cost is only half of ordinary cement). Steel slag phosphate fertilizer contains phosphorus and various trace elements, which is suitable for acid soil and can improve the soil, and can be used as a beverage additive. Its effective phosphorus pentoxide is 14 ~ 18%. The utilization of steel slag abroad focuses on water quenching in front of the furnace to make it granulate first; Or adopt a large-area layered slag laying method (thermal splashing method). Generally, steel slag returns to sintering or directly to blast furnace to replace limestone as cosolvent.

Radioactive material

The unstable nuclei of some elements undergo metamorphosis, releasing rays such as A, B (β) and C (in the form of energy) and becoming new atoms. This unstable element is called radioactive element, including natural (such as actinium, thorium and uranium) and man-made (plutonium, actinium and holmium). Substances containing radioactive elements are radioactive substances, which are of great value in industry, agriculture, medicine and national defense. However, it enters the human body through air, diet and other ways, and harms human health through internal or external irradiation. The human body is exposed to radioactive hazards, such as dizziness, fatigue, alopecia, erythema, leukopenia or increase, and thrombocytopenia; However, high-dose radiation can also cause leukemia, bone cancer, lung cancer and thyroid cancer and even death. Radioactivity can also cause gene mutation and chromosome aberration. Different rays do different harm to people. For example, the radioactive substance of σ- 1 particle will cause deep radioactive damage to the tissues it contacts; And-rays are mainly caused by external radiation; The penetration ability of β -rays is between the two, which can not only cause external radiation burns and skin deterioration, but also cause internal radiation damage through external tissues.