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While there is an estimated eight million tons of gold dissolved in the world’s oceans, the actual concentration of gold in seawater is only about 0.0000000006%, making it uneconomical to extract using any current technology. Gold is rare and unreactive, and large quantities of seawater would have to be evaporated to concentrate it sufficiently to be recovered by any conventional process. The only elements currently produced commercially from seawater are chlorine and bromine. Biological mining could potentially form the basis of future gold production, but this is highly speculative.
Yes, it is theoretically possible to extract gold from seawater, but it is not actually practical to do so. In total, there are estimated to be about eight million tons of gold dissolved in the world’s oceans. While this is a lot, the oceans are huge and the actual concentration of gold in seawater is only about 0.0000000006%. To put it another way, there is between 0.1 and 2.0 mg per ton, depending on location, making it uneconomical to extract using any current technology.
The sea as a source of minerals
Since the sea is fed by rivers that flow over soils containing metals, minerals and ores, a great variety of these can be found in seawater in the form of soluble compounds. Added to this is material from hydrothermal vents, fractures in geologically active areas of the ocean floor through which warm, mineral-rich water flows into the ocean. The concentration of different elements in the oceans depends not only on their abundance in terrestrial rocks, but also on their reactivity and solubility.
By far the most common metals in seawater are sodium, magnesium, calcium, and potassium, in that order. These are all very common, in combined form, in the earth’s crust and can form a variety of very water soluble compounds. Gold, in addition to being a rare element, is also very unreactive and does not readily form compounds that can find their way into the ocean by dissolving in water. For these reasons, the concentration of this metal in sea water is extremely low.
History
Gold was first detected in seawater in 1872 by British chemist S. Sonstadt and since then many people have promoted the idea of extracting the precious metal from the oceans. One of the most notable was the German chemist Fritz Haber, co-inventor of the Haber-Bosch process, who spent a portion of his career trying to devise a practical method of obtaining metal from seawater to pay for postwar Germany. debt. When it became clear how low the gold concentration actually was, he abandoned his efforts. Despite a series of hoaxes and scams, serious interest in the subject continues as gold reserves on the earth’s surface dwindle.
Extraction
Due to the extreme dilution of gold in seawater, there is currently no economically viable method of obtaining the metal from this source. Large quantities of seawater would have to be evaporated to concentrate it sufficiently to be recovered by any conventional process. This in itself would be energy intensive, with more energy and raw materials being consumed in the actual mining process. The cost would amount to much more than the value of the gold obtained.
The only elements currently produced commercially from seawater are the nonmetals chlorine and bromine. In the latter case, most of it is obtained from more concentrated non-marine brine deposits, but some is produced in Israel from the very salty waters of the Dead Sea. The concentrations of these elements in sea water are, however, enormously greater than those of gold.
In the past, iodine was obtained indirectly from the sea by processing seaweed, which concentrated the element. A similar form of biological mining could conceivably form the basis of a future means of gold production. Although algae don’t concentrate the metal, some other organisms, such as some types of bacteria, can. It is therefore possible that organisms of some kind, natural or genetically modified, could be used to recover gold from the sea, but this is highly speculative and may never become viable.
