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article imageAs tellurium demands rises, so do contamination concerns

By Karen Graham     Apr 25, 2018 in Technology
Demands for tellurium, a rare element, are on the rise. Some forms of tellurium are toxic, so as the element finds applications in solar panels, rubber production, electronics and more, there are rising concerns over contamination of the environment.
Tellurium is a rare, versatile, brittle and toxic element chemically related to selenium and sulfur. It is more commonly found in the universe than here on Earth, and its rarity is partly due to its high atomic number and also to its formation of a volatile hydride which caused it to be lost to space as a gas during the hot nebular formation of the planet.
As rare as tellurium may be, it can be found occasionally in its elemental form, as crystalline tellurium - silvery-white with a metallic luster. But it is more often found as the tellurides of gold - such as calaverite, krennerite, and sylvanite.
Science Daily reports that according to the U.S. Geological Survey, Canada is the leading supplier of tellurium to the U.S.
Tellurium crystal on sylvanite. Picture width 2 mm
Tellurium crystal on sylvanite. Picture width 2 mm
Christian Rewitzer
Demand and many uses of tellurium
With advances in technology, tellurium is finding its way into a vast array of applications, including solar panels, rubber production, electronics and more, even though its primary consumer is metallurgy in the making of iron, stainless steel, copper, and lead alloys.
Actually, you may be surprised to learn that tellurium is used as pigments in ceramics, and when mixed with selenium are used with barium peroxide as an oxidizer in the delay powder of electric blasting caps.
Thin-film PV array of cadmium telluride (CdTe) solar modules manufactured by U.S. company First Sola...
Thin-film PV array of cadmium telluride (CdTe) solar modules manufactured by U.S. company First Solar
Tellurite agar is used to identify members of the corynebacterium genus, most typically Corynebacterium diphtheriae, the pathogen responsible for diphtheria, while neutron bombardment of tellurium is the most common way to produce iodine-131.
With all the many uses we have found for tellurium, and the demand for this rare element growing, researchers are becoming concerned about possible environmental contamination. And because some forms of tellurium can be toxic to humans, Johan A. Wiklund, Jane L. Kirk and colleagues wanted to find out how widespread tellurium was in the environment.
The group of scientists represented the Aquatic Contaminants Research Division and National Laboratory of Environmental Testing, Environment Canada, Burlington, Ontario, and the Aquatic Contaminants Research Division, Environment Canada, Saskatoon, Saskatchewan,
American Chemical Society
Using lake sediment cores
The team collected and dated sediment cores from lakes in Canada near metal smelting operations, coal mining facilities, oil sands mining sites, rural locations and remote natural sites.
Concentrations of tellurium were steady or even low in rural Alberta, near oilsands sites. In a remote site in eastern Canada, core testing showed a "modest rise" during the 20th century. However, in a remote location in Toronto, modern tellurium deposit rates were found to be seven-fold higher in the 20th century.
This measurement was found to be compatible with tellurium concentration measurements in precipitation, leading the group to conclude that the atmospheric deposition history of tellurium, as well as anthropogenic activities, have significantly augmented atmospheric tellurium and was documented through the lake sediments.
Sediment cores give scientists a lot of information on past events as well as the concentration of d...
Sediment cores give scientists a lot of information on past events as well as the concentration of different deposits.
Hannes Grobe
How did the scientists come to this conclusion? Actually, it's simple. Using lake sediment cores, they were able to determine that tellurium concentrations were only high enough to be detectable after coal-fired electrical generation began in the area around 1910. The same goes for a copper smelting site. Tellurium concentrations increased over 100 times after the opening of the smelter in 1930.
As tellurium is growing in popularity, the researchers say that this study is a first step toward understanding how the element, a potential pollutant, can build up in the environment.
This very interesting research, "Widespread Atmospheric Tellurium Contamination in Industrial and Remote Regions of Canada," was published in the journal Environmental Science & Technology April 25, 2018.
More about tellurium, rare earth mineral, Canada, toxicity, lake sediments
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