COBALT

EKKEHARD SCHWAB, BASF

The name of the element cobalt has deep roots in the mythology of medieval mining. Mining was the basis for considerable wealth and power in regions where valuable metal ores were discovered. Myths were connected with the discovery of mineral resources, their extraction, and their processing. If one imagines medieval mining conditions--miners worked in almost complete darkness and under extremely dangerous circumstances--then it's not surprising that ghosts and demons were prevalent in people's minds in those days.

The word "cobalt" is derived from "Kobold," the name of a mischievous goblin in German mythology who, by the way, was closely related to another sprite called "Nickel." Kobold was not really evil, but he loved to tease humans. Typically, like Nickel, he was blamed when ores that looked like those of valuable metals could not be smelted. An example of such an ore is the mineral cobaltite [(Co,Fe)AsS], which is sometimes found together with elemental silver, and the following story is connected with this.

At the end of the 16th century, the yield of the silver mines in the German region of Saxony declined from year to year. Kobold was blamed for stealing the silver and leaving behind worthless rock. Around this time, a young man skilled in the art of smelting arrived in Schneeberg, one of the main mining towns, and started to experiment with the strange dead rock that was assumed to be silver ore. Because he often did this at night and behind closed doors, he aroused the suspicions of the townspeople. They were just about to arrest and sentence him as a wizard when he found a way to prepare a brilliant blue pigment. The people of Schneeberg quickly realized that although the young man had not found silver, he had discovered a valuable new material--cobalt blue, which is still one of the technical uses for cobalt.

In 2000, more than 35,000 tons of refined cobalt were produced worldwide, according to the British Geological Survey. The U.S. Geological Survey estimates that 45% is currently used in superalloys (chiefly for aerospace uses), 9% in magnet alloys, 9% in cemented carbides, 6% in other alloys including steel, and 30% in chemical and ceramic uses. In the field of audio and videotapes, addition of a few percent of cobalt allows magnetic iron oxides to be used for high-density recording. Consumption sectors that are expected to show strong growth in the future are hard-facing (cutting) alloys, carbides, catalysts, and rechargeable lithium-ion batteries, although here, however, cobalt is in competition with materials based on manganese and nickel. The irreplaceable material properties of superalloys and high-performance permanent magnets containing cobalt have caused the U.S. Defense Logistics Agency to stockpile strategic reserves of this once-undervalued element.

In the chemical industry, cobalt is an essential constituent in important catalysts. Together with molybdenum, it is used in hydrodesulfurization catalysts for the manufacture of clean fuels. Cobalt catalysts are employed in the production of Fischer-Tropsch hydrocarbons and in a number of special hydrogenation processes (for example, for the production of amines.) Last but not least, they are key components in the multi-million-pound technology of hydroformylation; that is, the catalytic transformation of olefins into aldehydes using homogeneous catalysts.

Finally, cobalt is an essential trace element in humans: About 40 ng of cobalt is required every day to meet the recommended dietary allowance of 2.4 mg of vitamin B₁₂.

Looking at the history of cobalt, it's clear that the element has undergone a significant transformation from an "ugly duckling" of no interest to miners into a "swan" of strategic industrial importance.

Ekkehard Schwab is a research director at BASF, Ludwigshafen, Germany. His research focuses on heterogeneous catalysis.

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