Cadmium

Extraction

Cadmium is a common impurity in precipitated out of the electrolysis solution.^[1]

Notable characteristics

Cadmium is a soft, malleable, zinc but reacts to form more complex compounds.

The most common oxidation state of cadmium is +2, though rare examples of +1 can be found.

Applications

About three-quarters of cadmium is used in plastics. Other uses include:

• Used in some of the lowest melting alloys.
• Due to a low coefficient of friction and very good fatigue resistance, it is used in bearing alloys.
• 6% of cadmium finds use in electroplating.
• Many kinds of solder contain this metal.
• As a barrier to control nuclear fission.
• Compounds containing cadmium are used in black and white television phosphors and also in the blue and green phosphors for color television picture tubes.
• Cadmium forms various Cadmium selenide can be used as red pigment, commonly called cadmium red. To painters who work with the pigment, cadmium yellows, oranges and reds are the most potent colours to use. In fact, during production these colours are significantly toned down before they are ground with oils and binders, or blended into watercolours, gouaches, acrylics, and other paint and pigment formulations. These pigments are toxic and it is recommended to use a barrier cream on your hands to prevent absorption through the skin when working with them. There is no such thing as cadmium blue, green or violet.
• Used in some HgCdTe is sensitive to infrared.
• Some cadmium compounds are employed in PVC as stabilizers.
• Used to block voltage-dependent calcium channels from fluxing calcium ions in molecular biology.

See also Cadmium compounds.

History

Cadmium (Latin cadmia, Greek καδμεία meaning "calamine", a Cadmium-bearing mixture of minerals, which was named after the Greek mythological character, Κάδμος (Cadmus)) was zinc carbonate (calamine) and for 100 years Germany remained the only important producer of the metal. The metal was named after the Latin word for calamine since the metal was found in this zinc compound. Strohmeyer noted that some impure samples of calamine changed color when heated but pure calamine did not.

Even though cadmium and its compounds are highly toxic, the British Pharmaceutical Codex from 1907 states that cadmium iodide was used as a medicine to treat "enlarged joints, scrofulous glands, and chilblains".

In 1927, the International Conference on Weights and Measures redefined the krypton).

Occurrence

      In 2001, China was the top producer of cadmium with almost one-sixth world share closely followed by South Korea and Japan, reports the British Geological Survey.

Cadmium-containing ores are rare and when found they occur in small quantities. steel scrap. Production in the United States began in 1907 but it was not until after World War I that cadmium came into wide use.

See also Category:Cadmium minerals.

A role of cadmium in biology has been recently discovered. A cadmium-dependent carbonic anhydrase has been found in marine diatoms. Cadmium does the same job as zinc in other anhydrases, but the diatoms live in environments with very low zinc concentrations, thus biology has taken cadmium rather than zinc, and made it work. The discovery was made using x-ray absorption fluoresence spectroscopy (XAFS), and cadmium was characterised by noting the energy of the x-rays which were absorbed.

 

Main article: isotopes of cadmium

Naturally occurring cadmium is composed of 8 radioactive isotopes have half-lives that are less than 2.5 hours and the majority of these have half-lives that are less than 5 minutes. This element also has 8 known meta states with the most stable being ^113mCd (t_½ 14.1 years), ^115mCd (t_½ 44.6 days) and ^117mCd (t_½ 3.36 hours).

The known isotopes of cadmium range in indium).

Toxicity

Main article: Cadmium poisoning

Cadmium is an occupational hazard associated with industrial processes such as metal plating and the production of nickel-cadmium batteries, pigments, plastics and other synthetics. The primary route of exposure in industrial settings is inhalation. Inhalation of cadmium-containing fumes can result initially in metal fume fever but may progress to chemical pneumonitis, pulmonary edema, and death.^[2]

Cadmium is also a potential environmental hazard. Human exposures to environmental cadmium are primarily the result of the burning of fossil fuels and municipal wastes.^[3] However, there have been notable instances of toxicity as the result of long-term exposure to cadmium in contaminated food and water. In the decades following World War II, Japanese mining operations contaminated the Jinzu River with cadmium and traces of other toxic metals. Consequently, cadmium accumulated in the rice crops growing along the riverbanks downstream of the mines. The local agricultural communities consuming the contaminated rice developed Restriction on Hazardous Substances (RoHS) directive, which bans carcinogens in computers.

Cadmium and several cadmium-containing compounds are known carcinogens and can induce many types of cancer.^[5]

Current research has found that cadmium toxicity may be carried into the body by calcium in certain biological systems, although these replacements are rare.

Tobacco smoking is the most important single source of cadmium exposure in the general population. It has been estimated that about 10% of the cadmium content of a cigarette is inhaled through smoking. The absorption of cadmium from the lungs is much more effective than that from the gut, and as much as 50% of the cadmium inhaled via cigarette smoke may be absorbed.

On average, smokers have 4-5 times higher blood cadmium concentrations and 2-3 times higher kidney cadmium concentrations than non-smokers. Despite the high cadmium content in cigarette smoke, there seems to be little exposure to cadmium from passive smoking. No significant effect on blood cadmium concentrations could be detected in children exposed to environmental tobacco smoke.

Precautions

While working with cadmium it is important to do so under a fume hood or with the use of an appropriate respirator to protect against dangerous fumes.^[6] Solder, for example, which may contain cadmium, should be handled with care.

References

1. ^ Cadmium at WebElements.com
2. ^ [1] Principles and Methods of Toxicology (fourth edition). A. Wallace Hayes. Taylor and Francis Publishing Inc.; Philadelphia, 2001.
3. ^ EPA summary on cadmium
4. ^ [2] Environmental cadmium exposure, adverse effects, and preventative measures in Japan. Nogowa et al. Biometals. 2004 Oct; 17(5):581-7.
5. ^ 11th Report on Carcinogens provided by the National Toxicology Program
6. ^ OSHA Solutions for workplace cadmium exposure

• IARC Monograph "Cadmium and Cadmium Compounds"
• National Pollutant Inventory - Cadmium and compounds
• WebElements.com – Cadmium
• Los Alamos National Laboratory – Cadmium
• [3] Warning Moose and Deer Liver
• National Institute for Occupational Safety and Health - Cadmium Page