Can Gold be Extracted from Seawater?

In the early portion of the 20th century, chemists hoped they could develop a process to recover pure gold from large quantities of seawater, making themselves and their countries rich. German chemist Fritz Haber, famous co-inventor of the Haber-Bosch process, spent a portion of his career attempting to extract gold from the sea to pay for Germany’s post-WWI debt.

It is a fact that a typical cubic mile of seawater contains, on average, 1-2 parts per million (ppm) of gold. The problem lies in getting the gold separated from the water. A cubic mile (1.6 cubic km) of seawater is an almost unimaginable quantity from the human perspective. It would take decades for us to process it, considering the current capacities of our technology. From the perspective of chemists in the early 20th century, it must have seemed like an even larger quantity. Nevertheless, the lure of gold is great, and throughout history people have spent their lives trying to get it, whether through stealing it, transmuting it from lead, or extracting it from seawater.

Of course, these chemists failed in their endeavor. Successfully extracting the gold would require a series of massive centrifuges, so costly that the gold extracted would never be able to pay for their construction.

It turns out that the only mineral that can be extracted from the ocean profitably is salt. A cubic mile of seawater’s worth of salt, it turns out, is enough to supply the entire world for upwards of a year �128 million tons. We extract it by collecting it in areas where seawater evaporates, leaving salt deposits behind. The ancient Chinese did this as long as three thousand years ago. Today, we get most of our salt from brine wells and salt domes, which were created millions of years ago when ancient seas evaporated.

The only metal that has ever been successfully isolated in significant quantities from seawater is manganese. In some areas of the world, the ocean bottom is covered in many trillions of manganese nodules, the dust of which is dissolved in the sea water. In fact, as much as 1/1000th of seawater, by weight, is manganese.

There is so much manganese in the ocean that it is the primary source for many large countries, such as the United States. The extraction process is simple. It may not be gold, but it does come in handy.