Cadmium,Heavy non-ferrous metalsElement, chemical symbol Cd, atomic number 48, discovered in 1817.The simple substance is silver white metal, which is an absorptionneutronFine metal, which can be made into bars innuclear reactorInternal slowdownfission chain reaction And it is very useful in zinc cadmium battery.itssulfideBright color, used to makeCadmium yellowPigment.
CrustThe ratio of medium to cadmium is 1000000:0.1~1000000:0.5.Is as a by-product from zinc ore orSulfochromiteIt is mainly used to protect other metals from corrosion and rust, such aselectroplateSteel, iron products, copper, brass and other alloys.Another use is to produce a bright yellow pigment called cadmium yellow, which can be used as high-grade paint and painting pigment.
On July 23, 2019, cadmium and cadmium compounds were included in the list of toxic and harmful water pollutants (the first batch).[1]
On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily sorted out for reference. Cadmium and cadmium compounds are included in the list of Class 1 carcinogens.[3]
Chinese name
cadmium
Foreign name
Cadmium
CAS login number
7440-43-9
EINECS login number
231-152-8
Melting point
321 ℃
Boiling point
765 ℃
Density
8.65 g/cm³
Appearance
Silver white metal
Security description
S60；S61
Hazard symbol
R20/21/22；R50/53
Hazard description
Xn
Atomic volume
13.1cmthree/mol
Symbol
Cd
Atomic radius
151 pm
Covalent radius
144±9 pm
Vander Waals radius
158 pm
Heat of fusion
6.21 KJ/mol
Atomic number
forty-eight
Specific heat capacity
(25 °C) 26.020 J/(kg·K)
Electronic layout
[Kr]4dten5stwo
Element Category
transition metal
Cycle
Fifth cycle
family
Family IIB
area
Zone d
Common valence
0，+1，+2
Electronegativity
1.69 (Pauling scale)
Atomic weight
one hundred and twelve point four one one zero zero
In 1817, Stromel, Germany, was not purezinc oxideThe brown powder is separated from thecharcoalCo heating to produce cadmium.
The first person to discover cadmium was Stromel, professor of chemistry and medicine at the University of Gottingen in Germany.He also serves as the inspection commissioner of drug dealers entrusted by the government.It was during his inspection of the drugstore that he observed problems in zinc containing drugs, which prompted him to discover cadmium in 1817.Since the new metals found exist in zinc ores, they are treated as zinc bearing oresSmithsoniteCalamine names it Cadmium, and the element symbol is Cd.
Cadmium was discovered much later than its homologous elements mercury and zinc.Its content in the crust is more than that of mercury, but once mercury appeared, it attracted people's attention with its strong metallic luster, large proportion, special mobility and the attitude of being able to dissolve multiple metals.The content of cadmium in the crust is much less than that of zinc, and it is often contained in zinc ores in a small amount, and rarely mineralizes alone.Cadmium is more volatile than zinc, so when smelting zinc at high temperature, it escapes earlier than zinc, avoiding people's awareness.This means that cadmium cannot be discovered before zinc.
Physical and chemical properties
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physical property
cadmium
Cadmium is a silvery white lustrous metal with melting point of 320.9 ℃, boiling point of 765 ℃ and density of 8650kg/mthree。Toughness andDuctility。Cadmium in humid airSlow oxidationAnd loseMetallic lusterWhen heated, a brown oxide layer is formed on the surface. If heated above the boiling pointCadmium oxideSmoke.Cadmium andhalogenThe reaction is intense, formingCadmium halide。It can also be directly combined with sulfur to formCadmium sulfide。Cadmium is soluble in acid, but insoluble in alkali.CadmiumOxidized stateIs+1,+2.Cadmium oxideandCadmium hydroxideThey are soluble in acid, but insoluble in alkali.Cadmium can form a variety ofCoordination ion, such as Cd (NHthree）, Cd (CN), CdCl, etc.
It can be reduced from cadmium containing soot or cadmium residue (such as coal or carbon or sulfuric acid) by various methodsLeaching methodAnd zinc powder).Available for further purificationElectrolytic refiningAnd vacuum distillation.Cadmium is mainly used for steel, iron, copperbrassAnd other metalselectroplate, YesAlkaline substanceGood corrosion resistance.Cadmium can be used to make batteries with small volume and large capacitance.Cadmium compounds are also widely used in the production of pigments andPhosphor。Cadmium sulfide、Cadmium selenide、Cadmium tellurideFor manufacturingPhotocell。
chemical property
Reaction of cadmium with air
Cadmium can be burned in air to produce cadmium oxide (Ⅱ), and the color of cadmium oxide changes with the reaction conditions.[4]
Reaction of cadmium with halogen
Cadmium fluoride (Ⅱ) (CdF ₂), cadmium bromide (Ⅱ) (CdBr ₂) and cadmium iodide (Ⅱ) (CdI ₂) can be produced by the direct reaction of metal cadmium with fluorine, bromine and iodine.[4]
Determination method
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The cadmium content of most fresh water in the field of environmental engineering is less than 1 μ g/L, and the average solubility of cadmium in seawater is 0.15 μ g/L.The main pollution source of cadmium is wastewater discharged from electroplating, mining, smelting, dyes, batteries and chemical industry.
Battery production is the largest consumption area of cadmium, accounting for more than 70% of the total consumption of cadmium.Cadmium is used for electroplating of steel, iron, copper, brass and other metals.Cadmium, as a basic component of alloy, can be prepared into many alloys, such as special fusible alloy, wear-resistant alloy and solder alloy, which can be used as electroplating anti-corrosion coating of steel structure, control rod of atomic reactor, photocell and manufacturing pigment, plastic stabilizer, electrical contact material, solder, printed circuit board, optical glass, fluorescent powder, etc.Cadmium compounds can also be used in pesticide, bactericide, paint and other manufacturing industries.Cadmium plays an important role in pigment production, ceramics manufacturing and other fields.[5]
Distribution
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CadmiumSulfochromiteIt occurs in zinc ore, lead zinc ore, copper lead zinc ore.Cadmium resources are mainly distributed in Australia, the United States, China, CanadaKazakhstanMexico, Peru, Japan, Russia, Germany, India and other countries.China's proven cadmium resources account for more than 20% of the world's total cadmium resources, ranking first in the world, mainly distributed in Yunnan, Sichuan, Guangdong, Hunan, Guangxi, Gansu and other provinces and regions.Yunnan accounts for about 50% of China's cadmium reserves.Since cadmium is associated with lead, zinc and copper ores, the resource potential of cadmium ores depends on the resource potential of lead and zinc ores.fromNickel cadmium batteryThe recovered cadmium accounts for more than 15%.[5]
Biotoxicity
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Cadmium will stimulate the respiratory tract. Long term exposure will cause anosmia, gingival macula or gradually forming the yellow circle. Cadmium compounds are not easy to be absorbed by the intestinal tract, but can be absorbed by the body through breathing and accumulated in the liver or kidney, causing harm, especially to the kidney.It can also cause osteoporosis and softening.
harm
Identification of cadmium containing substances
There are acute and chronic poisoning.Inhalation of cadmium gas can cause respiratory symptoms, and oral intake of cadmium can cause liver and kidney symptoms.
Cadmium is not humanRequired Elements。Cadmium in the human body is absorbed from the external environment after birth, and is mainly accumulated in the body through food, water and air.
Absorption and metabolism of cadmium The smoke and dust of cadmium can be inhaled through the respiratory tract.The amount of cadmium absorbed in the lung accounts for 25~40% of the total amount of cadmium.20 cigarettes a day can inhale 2-4 μ g of cadmium.The absorption rate of cadmium through the digestive tract is related to the type and intake of cadmium compounds and whether other metals are taken together.For example, when the intake of calcium and iron is low, the absorption of cadmium can be significantly increased, while when the intake of zinc, the absorption of cadmium can be inhibited.Cadmium absorbed into the blood is mainly related tored blood cellcombination.
The liver and kidney are the two major organs storing cadmium in the body, and the cadmium contained in them accounts for about 60% of the total cadmium in the body.It is estimated that the total amount of cadmium in the body of normal people aged 40-60 is about 30mg, of which 10mg is in the kidney, 4mg is in the liver, and the rest is distributed in the lungs, pancreas, thyroid, testis, hair, etc.Cadmium content in organs and tissues can be determined by regionenvironmental pollutionThe situation varies greatly and increases with age.
Cadmium entering the body is mainly excreted by the kidney through urine, but a considerable amount is also excreted by the liver through bile with feces.The excretion rate of cadmium is very slow. Biology of cadmium in human renal cortexhalf lifeIt is 10 to 30 years.
clinical manifestation
Bone pain and cadmium poisoning
Cadmium and its compounds have certain toxicity.Inhalation of cadmium oxide smoke can produceacute poisoning。Early symptoms of poisoning include sore throat, cough, chest tightness, shortness of breath, dizziness, nausea, body aches, weakness, fever, etcToxic pulmonary edemaOr chemical pneumonia, with obviousdyspnea, chest pain, cough, a lot of foamy blood colored sputum, which may be caused byacute respiratory failure And death.When acidic food or drink is prepared or stored with cadmium plated utensils, cadmium may be contained in the diet, and acute cadmium poisoning may also be caused after ingestion.The incubation period is short, and nausea, vomiting, abdominal pain, diarrhea and other symptoms can occur after 10-20 minutes.In severe cases, dizziness, sweating, prostration, upper limb hypoesthesia, and even convulsion and shock may occur.It usually takes 3-5 days to recover.
Long term inhalation of cadmium can cause chronic poisoning and kidney damage, which is mainly manifested in the presence of a large amount of low molecular weight protein in the urine. Although the filtration function of the glomerulus is mostly normal, the recovery function of the renal tubules is reduced, and the excretion of cadmium in the urine is increased.
Emphysema, anemia and bone changes of cadmium exposed workers have also been reported, but the exact relationship between these changes and cadmium exposure is still uncertain.It is also reported abroad that the incidence of prostate cancer among workers exposed to cadmium oxide is high.
acute
It is not difficult to diagnose acute cadmium poisoning according to exposure history and respiratory symptoms.In addition to occupational history and clinical symptoms, the diagnosis of chronic cadmium poisoning was made by combining chest radiograph, pulmonary function, renal tubular function and urinary cadmium.
Acute cadmium poisoning is caused by inhalation. The symptoms of upper respiratory tract mucous membrane irritation first appear, and the above symptoms will be alleviated after disengagement.After the incubation period of 4 to 10 hours, cough, chest tightness, dyspnea, chills, muscle and joint pain in the back and limbs, flaky shadows and thickened lung markings were found in chest X-ray examination.Severe patient has pulmonary edema andheart failure。The clinical manifestations of poisoning caused by oral cadmium compounds are similarAcute gastroenteritis, nausea, vomiting, abdominal pain, diarrhea, general weakness, muscle soreness, and collapse in severe cases.
chronic
The early renal damage of chronic cadmium poisoning is manifested by low molecular protein in urine（β 2-microglobulin、Vitamin A binding protein, lysozyme, ribonuclease, etc.), and glucose urine, high amino acid urine and high phosphate urine may also appear.Occurrence of advanced patientsChronic renal failure。Pulmonary manifestations are chronic and progressiveObstructive emphysema, eventually leading to the decline of lung function.Chronic poisoning patients are often accompanied by macula in the neck of teeth, loss of olfaction, ulcer and atrophy of nasal mucosa, and othersAnorexiaNausea, weight loss and hypertension.The incidence of lung cancer was increased in long-term exposure to cadmium.
Japan reported that a chronic cadmium poisoning caused by ingestion of cadmium contaminated water sources is called "pain".The clinical manifestations are back and leg pain, abdominal distension andindigestion, multiple in severe patientsPathological fracture。Laboratory examination showed renal tubular reabsorption dysfunction, increased urinary calcium and phosphate excretion, and decreased blood calcium.The epidemiological investigation of pain is related to cadmium.Pain is more common in women of childbearing age, so it is considered that there are stillNutritional deficiency, calcium loss and endocrine factors.
prevention and cure
The treatment of acute poisoning caused by inhaling a large amount of cadmium oxide smoke is the same as that of common irritating gas poisoning.The key is to prevent pulmonary edema.
Evacuate the accident site as soon as possible, keep quiet, lie in bed and breatheoxygenKeep the respiratory tract unblocked, use 10% silicone atomization inhalation to eliminate foam,Adrenocortical hormoneIt can reduce the permeability of capillaries and should be used quantitatively at an early stage.Limit fluid intake and give antibiotics to preventSecondary infectionIn case of acute ingestive cadmium poisoning, symptomatic treatment is mainly adopted, and a large amount of fluid infusion and atropine injection are given to stop vomiting and eliminate abdominal pain.
In case of kidney damage caused by chronic cadmium poisoning, the intake of calcium and phosphate should be increased in the diet, and sufficient zinc, protein and metal complexing agent should be providedCalcium disodium edetate（CaNatwo-EDTA) can increase the excretion of cadmium, but can aggravate renal damage.It is not recommended to use in case of acute or chronic poisoning.Reported oralAzotriacetic acid(NTA) can promote the excretion of cadmium (mainly through feces), thus reducing the accumulation in the body without damaging the renal function.
In order to prevent cadmium poisoning, places where cadmium and its compounds are smelted and used should have good ventilation and airtight devices.In addition to the necessary ventilation equipment, the welding and electroplating processes shall wear personal gas masks during operation.Do not eat or smoke in the production site.The maximum allowable concentration of cadmium oxide in production sites specified by China is 0.1mg/mthree。
Cadmium pollution of soil can cause public nuisance, pain and disease.The pollution of cadmium to soil mainly comes in two forms: one is that the cadmium in industrial waste gas diffuses around with the wind and accumulates in the soil around the factory after natural sedimentation; the other is that the industrial waste water containing cadmium irrigates farmland to pollute the soil with cadmium.Therefore, in order to prevent cadmium from polluting the environment, we must do a good job in environmental protection and strictly implement the environmental health standards of cadmium.
safety standards
european union
The EU lists cadmium as a highly hazardous toxic substance and carcinogenic substance and regulates it.
U.S.A
The United States Environmental Protection Agency limits the amount of cadmium discharged into lakes, rivers, abandoned sites and farmland, and bans cadmium in pesticides.The United States Environmental Protection Agency allows 10 ppb of cadmium in drinking water, and intends to reduce the limit to 5 ppb.The United States Food and Drug Administration stipulates that the cadmium content of food coloring shall not exceed 15ppm.The US Occupational Safety and Health Administration stipulates that the cadmium content in the air of the working environment is 100 μ g/m3 in smoke and 200 μ g/m3 in cadmium dust.The United States Occupational Safety and Health Administration plans to limit the content of all cadmium compounds in the air to 1 to 5 micrograms/cubic meter. The National Institute of Occupational Safety and Health hopes that workers will breathe as little cadmium as possible to prevent lung cancer.
Pollution incident
From 1930 to 1960, some cadmium pollution occurred in the Shentongchuan River Basin, Toyama Prefecture, Japan.Cadmium containing wastewater discharged from Shiyuan Zinc Smelting Plant has polluted the surrounding farmland and water sources.
In May 2004, employees of two battery factories in Huizhou, Guangdong Province were tested for high levels of cadmium in blood and urine. As of August 3 of the same year, 1021 employees of two enterprises had been tested, 177 of whom had exceeded the cadmium standard, and 2 had cadmium poisoning.
In August 2009, the cadmium pollution in Zhentou Town, Liuyang City, Hunan Province was caused by the production of secondary zinc oxide and zinc sulfate in Changsha Xianghe Chemical Plant, but there was no complete sewage discharge facilities.As of August 2, 2009, the plant was permanently closed.
In January 2012, Guangxi Longjiang River was polluted by cadmium.On January 31, 2012, experts involved in the accident disposal from the Guangxi Longjiang River Emergency Response Headquarters for Environmental Emergencies estimated that the cadmium leakage in this cadmium pollution event was about 20 tons.Experts said that the amount of cadmium leakage is rare in all previous heavy metal environmental pollution incidents in China, and the pollution incident will affect about 300 kilometers of the river.
In February 2012, a report on the "hidden hazards of heavy metals in cosmetics" by the Canadian environmental protection organization tested 49 well-known brands of cosmetics, including Clinique's foundation and L'Oreal mascara.The researchers mainly tested whether these cosmetics contained eight toxic substances, namely arsenic, cadmium, lead, mercury, beryllium, nickel, selenium and thallium. Among them, the last four chemicals are prohibited in Canada.It was found that, except for mercury, almost all cosmetics tested contained the other seven toxic substances.Among them, Clinique's magic oil control foundation liquid contains six toxic substances: arsenic, beryllium, cadmium, nickel, lead and thallium. Another well-known cosmetics brand, L'Oreal's mascara "Bare Natural", has also been detected to contain six toxic substances like Clinique.In addition, Cover Girl's ultra perfect eyeliner contains beryllium, cadmium, nickel and lead.[2]
On June 17, 2012, Rizhao Inspection and Quarantine Bureau of Shandong Province implemented the return treatment for a batch of 24 tons of imported saury from Japan with excessive heavy metal cadmium content.According to reports, this batch of saury was reported for inspection in May, with a total of 2400 cases and 24000 kg, worth 4.56 million yen (about 310000 yuan).
On March 4, 2013, a star product of the famous Japanese cosmetics brand Shiseido, "Anresa Sunscreen", was detected to contain cadmium. Anresa series has been popular in China for many years and has won the first place in the sales list of merchants for many times. Its products include golden bottle sunscreen, whitening sunscreen, bright sunscreen, mild sunscreen, etc.
In May 2013, according to the food sampling inspection in Guangzhou catering sector, 45% of Hunan rice and rice products were found to have exceeded the cadmium standard.
security information
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Safety terminology
S60：This material and its container must be disposed of as hazardous waste.
The substance and its container must be disposed of as hazardous waste.
S61：Avoid release to the environment. Refer to special instructions / safety data sheets.
Avoid release to the environment.Refer to Special Instructions/Safety Data Sheet.
Risk terminology
R20/21/22：Harmful by inhalation, in contact with skin and if swallowed.
Harmful by inhalation, skin contact and if swallowed.
R50/53：Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
It is extremely toxic to aquatic organisms and may have long-term adverse effects on the water environment.
