The oceans are gigantic masses of water. A lot of salt is dissolved in them, but also other minerals - including gold. There have long been considerations of extracting the precious metal from water. But how much gold is actually in the oceans?
At some point someone came up with the idea that there must be more than just salt dissolved in seawater. At the end of the 19th century, it was finally confirmed that gold atoms also float in sea water. Exactly how many was unknown for a long time. Nevertheless, early on people had hopes for fabulous riches that could be salvaged from the sea water.
The German chemist and Nobel Prize winner Fritz Haber wanted to raise the supposed pot of gold in the sea as early as the 1920s. The proceeds were intended to pay off Germany's debts from the First World War. But nothing came of it. Because Haber assumed the wrong gold content. It was not until 1990 that researchers K. Kenison Falkner and J.M. Edmond to accurately determine the concentration of the precious metal in seawater. Which also allowed for a better estimate of the total occurrence. So how much gold is dissolved in sea water?
Nobody knows for sure. But Sylvia Sander, Professor of Marine Mineral Resources at the GEOMAR Helmholtz Center for Ocean Research in Kiel, considers the 1990 study to be a good basis for calculations. However, this revealed a significantly lower gold concentration than had previously been hoped for. "The concentration of most metals in the ocean is extremely low, but especially that of gold," says Sander to ntv.de. On average, it is only ten picograms - trillionths of a gram - of gold per kilogram of seawater. "That's three times nothing."
But the amount of all the water in the world's oceans is enormous. It is estimated at a total of 1.3 trillion tons. In total - despite the vanishingly low concentration - there is still quite a bit of gold. "A total of 10 to 20 thousand tons could be dissolved in the seawater," says Sander. For comparison: Since the beginning of human history, around 200,000 tons of gold have been mined worldwide.
So there is gold floating in the sea worth - based on the current market value - more than 600 billion euros. Which leads to the question: Can't these riches be found? Sander waves it off. "It would take so much energy and effort to extract the gold from seawater that it would be completely uneconomical." The same applies to platinum, which - although also very valuable - can be found in similarly low concentrations in seawater. "It will probably never be possible to extract these raw materials from seawater in a meaningful way," says the expert.
In the 1920s, Nobel Prize winner Fritz Haber also failed due to the enormous costs of extracting sea gold. His project was abandoned after several test runs across the Atlantic. Germany was left with its war debts.
Nevertheless, in the recent past there have been interesting approaches to extracting gold dissolved in water, says Sander. For example, the idea of Swiss chemists to use a molecular sponge to filter gold ions out of the water and form them into small nuggets. The good thing: The production of the material for the sponge is relatively cheap. However, the process works primarily with small amounts of water - the larger it gets, the longer it takes. "It could be used where the concentration of gold is significantly higher for natural reasons, such as in certain rivers or where gold is discharged into water by humans," says Sander.
Incidentally, rivers are the second important natural source of gold in the oceans - in addition to hydrothermal vents on the sea floor, so-called black smokers. The concentration of gold in the sea is particularly high in their vicinity.
By the way: Gold is not the only raw material dissolved in the sea that inspires people's imagination. Around four billion tons of uranium are believed to be in the lake water, which is significantly more than gold. According to calculations, this could cover the energy needs of mankind for the next 10,000 years. Several research groups around the world have tested new materials in recent years to filter uranium from seawater. The yield so far has been low. Still, some see economic potential in marine uranium.
(This article was first published on Saturday, November 12, 2022.)
