Кадмий химические свойства, назначение, производство
Описание
Cadmium is a grey-white, soft, blue-white malleable, lustrous metal. It is insoluble in cold water, hot water, methanol, diethyl ether, and n-octanol. It is stable and incompatible with strong oxidising agents, nitrates, nitric acid, selenium, and zinc, and the powdered metal may be pyrophoric and flammable.
Cadmium is associated with occupations such as industrial processes, metal plating, and production of nickel– cadmium batteries, pigments, plastics, and other synthetics. Cadmium metal is produced as a by-product from the extraction, smelting, and refining of the non-ferrous metals zinc, lead, and copper. In view of the unique properties, cadmium metal and cadmium compounds are used as pigments, stabilisers, coatings, specialty alloys, and electronic compounds.
Химические свойства
Calmium is an odorless, silver-white lustrous metal with a bluish tinge, which is ductile and highly malleable with a melting point of 321 °C. The metal is soft enough to cut with a knife and will tarnish in air; as a powder, cadmium is flammable. Burning cadmium results in an odorless yellowbrown cadmium fume (cadmium monoxide or cadmium oxide fume) composed of finely divided particles dispersed in air. Both cadmium and cadmium oxide are insoluble in water and have a vapor pressure of approximately 0 mmHg. Cadmium is insoluble in water but can be solubilized in acid. Cadmium salts (e.g., cadmium sulfate and cadmium chloride) are soluble in water.
Физические свойства
Cadmium is a soft, blue-white metal that is malleable and ductile although it becomesbrittle at about 80°C. It is also found as a grayish-white powder. It is considered rare and isseldom found by itself as an ore. Its melting point at 320.9°C is considered low. Its boilingpoint is 765°C, and its density is 8.65 g/cm3. Certain alloys of cadmium have extremely lowmelting points at about 70°C.
Изотопы
There are 52 isotopes of cadmium. Forty-four are radioactive and artificiallyproduced, ranging from Cd-96 to Cd-131. Of these 52 isotopes, there are five stableisotopes plus three naturally occurring radioactive isotopes with extremely long half-livesthat are considered as contributing to the element’s natural occurrence in the Earth’scrust. The three naturally radioactive isotopes (Cd-106, Cd-113, and Cd-116) are thelongest known beta emitters. They are two million years older than when the solar systemwas formed about 4.5 billion years ago. The five stable isotopes and their proportionalcontributions to the element’s existence on Earth are as follows: Cd-108 = 0.89%,Cd-110 = 12.49%, Cd-111= 12.80%, Cd-112 = 24.13%, and Cd-114 = 28.73%.
Происхождение имени
The word cadmium is from the Latin word cadmia or the Greek word
kadmeia, meaning the zinc oxide ore “calamine” that contains the element cadmium.
Вхождение
Cadmium is considered a rare element even though it is widely distributed over the Earth’scrust. Its estimated abundance in the Earth’s crust is 1.10-1 milligrams per kilogram. It is consideredthe 65th most abundant element, but it does not occur as a free metal in nature. It isusually found in relationship with other metallic ores. Its abundance is only about 1/1000ththat of zinc. It is found in an ore called greenockite, which is cadmium sulfite (CdS). This oredoes not have a high enough concentration of cadmium to be mined profitably. Cadmiumis found along with zinc, lead, and copper ores. Today, most cadmium is obtained as a byproductfrom the processing and refining of zinc ores. In addition, dust and fumes from roastingzinc ores are collected by an electrostatic precipitator and mixed with carbon (coke) andsodium or zinc chloride. This residue is then treated to recover the cadmium. Other refiningprocesses can obtain up to 40% recovery of cadmium from zinc ores.
Greenockite ore, as well as zinc and other ores, which produce cadmium as a by-product,are found in many countries, including Australia, Mexico, Peru, Zaire, Canada, Korea, andBelgium-Luxembourg and in the central and western United States.
Характеристики
Although cadmium is not considered a transition element in some periodic tables, it is thecentral element of the triad with zinc and mercury. Zinc is just above it and mercury is below itin group 12 of the periodic table. Cadmium’s chemical and physical properties are similar to itsgroup 12 mates. Their electronegativity is very similar: Zn = 1.6, Cd = 1.7, and Hg = 1.9.
Cadmium is resistant to alkalis, but is soluble in acids, mainly nitric acid. Although it isused to electroplate steel to prevent corrosion, it will tarnish in moist air.
Использование
A soft bluish metal, cadmium is extremely toxic, particularly in the compounds used for photography. It is found in zinc ores and in the mineral greenockite (CdS).
Определение
cadmium: Symbol Cd. A soft bluishmetal belonging to group 12 (formerlyIIB) of the periodic table; a.n.48; r.a.m. 112.41; r.d. 8.65; m.p.320.9°C; b.p. 765°C. The element’sname is derived from the ancientname for calamine, zinc carbonateZnCO3, and it is usually found associatedwith zinc ores, such as sphalerite(ZnS), but does occur as themineral greenockite (CdS). Cadmiumis usually produced as an associateproduct when zinc, copper, and leadores are reduced. Cadmium is used inlow-melting-point alloys to make solders,in Ni–Cd batteries, in bearingalloys, and in electroplating (over50%). Cadmium compounds are usedas phosphorescent coatings in TVtubes. Cadmium and its compoundsare extremely toxic at low concentrations;great care is essential wheresolders are used or where fumes areemitted. It has similar chemical propertiesto zinc but shows a greater tendencytowards complex formation.The element was discovered in 1817by F. Stromeyer.
Общее описание
Silver-white blue tinged lustrous metallic solid.
Реакции воздуха и воды
The finely divided metal is pyrophoric. Slowly oxidized by moist air to form CADMIUM oxide. Insoluble in water.
Профиль реактивности
A violent explosion occurred 30 minutes after placement of a CADMIUM rod into hydrazoic acid [Mellor 8 Supp. 2:50 1967]. Fused ammonium nitrate with powdered metal often produces a violent explosive reaction. Reactivity similar to zinc. May be incompatible with oxidants.
Опасность
Cadmium powder, dust, and fumes are all flammable and toxic if inhaled or ingested.Cadmium and many of its compounds are carcinogenic.
Severe illness and death can occur from exposure to many cadmium compounds. It isabsorbed in the gastrointestinal tract. However, it can be eliminated in the urine and fecesin young, healthy people.
Пожароопасность
Flammable in powder form. Combustible.
Промышленное использование
Cadmium (symbol Cd) is a silvery-white crystallinemetal that has a specific gravity of 8.6,is very ductile, and can be rolled or beaten intothin sheets. It resembles tin and gives the samecharacteristic cry when bent, but is harder thantin. A small addition of zinc makes it very brittle.It melts at 320°C and boils at 765°C. Cadmiumis employed as an alloying element insoft solders and in fusible alloys, for hardeningcopper, as a white corrosion-resistant platingmetal, and in its compounds for pigments andchemicals. It is also used for Ni–Cd batteriesand to shield against neutrons in atomic equipment;but gamma rays are emitted when theneutrons are absorbed, and these rays requirean additional shielding of lead.
Most of the consumption of cadmium is forelectroplating. For a corrosion-resistant coatingfor iron or steel a cadmium plate of 0.008 mmis equal in effect to a zinc coat of 0.025 mm.The plated metal has a silvery-white color witha bluish tinge, is denser than zinc, and harderthan tin, but electroplated coatings are subjectto H2 embrittlement, and aircraft parts are usuallycoated by the vacuum process. Cadmiumplating is not normally used on copper or brasssince copper is electronegative to it, but whenthese metals are employed next to cadmium-plated steel a plate of cadmium may beused on the copper to lessen deterioration.
Профиль безопасности
Confirmed human
carcinogen with experimental carcinogenic,
tumorigenic, and neoplastigenic data. A
human poison by inhalation and possibly
other routes. Poison experimentally by
ingestion, inhalation, intraperitoneal,
Канцерогенность
Cadmium and cadmium compounds are known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans, including epidemiological and mechanistic studies. Cadmium and cadmium compounds were first listed as reasonably anticipated to be human carcinogens in the First Annual Report on Carcinogens in 1980, based on sufficient evidence of carcinogenicity from studies in experimental animals. The listing was revised to known to be human carcinogens in the Ninth Report on Carcinogens in 2000.
Экологическая судьба
Cadmium inhibits plasma membrane calcium channels and
Ca2t-ATPases. It also inhibits repair of DNA damaged by
various chemicals, an effect which is believed to be associated
with the induction of tumors. Although cadmium forms
a metallothionein, the preformed cadmium metallothionein is
nephrotoxic (toxic to the kidneys); it is suggested that effects
occur when, at some stage in the kidney, the cadmium is
dissociated from the metallothionein. In Itai-Itai disease (see
Human under Chronic Toxicity section), patients were found
to have chromosome abnormalities.
Cadmium has an affinity for sulfhydryl groups, and hence
can inhibit enzymes; however, cells treated with cadmium
showed proliferation of peroxisomes, which contain catalase,
an enzyme. It appears that cadmium at first inhibits catalase
activity and then, after a time, enhances that activity. In addition,
cadmium inhibits enzymes involved in gluconeogenesis
(the generation of glycogen for energy production from noncarbohydrate
precursors). It also inhibits oxidative phosphorylation
(energy production) and depresses trypsin inhibitor
capacity.
хранилище
Cadmium should be kept stored in a tightly closed container in a cool place. It should be
kept stored in a separate locked safety storage cabinet
Перевозки
UN2570 Cadmium compounds, Hazard Class:
6.1; Labels: 6.1-Poisonous materials, Technical Name
Required.
Методы очистки
Any oxide contaminant is removed by filtering the molten metal, under vacuum, through quartz wool. Its solubility in Hg is 5.2% (18o), and it is soluble in mineral acids. [Wagenknecht & Juza in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1092 1965.]
Структура и конформация
The space lattice of Cadmium belongs to the hexagonal system, and its closely-packed hexagonal lattice has lattice constants of a=0.2973 nm and c=0.5607 nm.
Несовместимости
Air exposure with cadmium powder may
cause self-ignition. Moist air slowly oxidizes cadmium
forming cadmium oxide. Cadmium dust is incompatible
with strong oxidizers, ammonium nitrate; elemental sulfur;
hydrazoic acid; selenium, zinc, tellurium. Contact with
acids cause a violent reaction, forming flammable hydrogen
gas.
Утилизация отходов
With cadmium compounds in
general, precipitation from solution as sulfides, drying and
return of the material to suppliers for recovery is recommended. Cadmium may be recovered from battery scrap as
an alternative to disposal. In accordance with
40CFR165, follow recommendations for the disposal of
pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting
your local or federal environmental control agency, or by
contacting your regional EPA office.
Меры предосторожности
On exposures to cadmium, wash the skin immediately with plenty of water and a nonabrasive soap. Workers should cover the exposed skin with an emollient.
Кадмий препаратная продукция и сырье
сырьё
препарат