A research team such as the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has developed a special method for extracting a small amount of "gold" dissolved in hot springs.
Attention is focused on whether it can be established as a new collection method other than mining.
It was developed by a research team of the Japan Agency for Marine-Earth Science and Technology and a major machine manufacturer, IHI.
"Gold" is mainly contained in magma deep underground, and after it melts into the hot water of several hundred degrees that flows around it, it rises to the surface over a long period of time and cools and solidifies. believed to be a mine.
Since gold dissolves in hot water, the research team considered that it is also contained in hot springs, and searched for a way to recover it, focusing on a type of algae called cyanobacteria.
This "cyanobacterium" separates the "gold" dissolved in the hot springs and the chlorine that binds to it, and has the property of adsorbing only "gold". , An experiment was conducted in which a special sheet processed with "cyanobacteria" was soaked, and "gold" was collected.
At the highest concentration, 30 ppm = about 30 grams per ton of sheet.
Since the amount that can be extracted from 1 ton of ore in the world's major gold mines is about 3 to 5 grams, we plan to conduct further experiments as it may become a new method of collecting "gold".
Tatsuo Nozaki, a senior researcher at the Japan Agency for Marine-Earth Science and Technology, said, "Although this was the first analysis, we confirmed that gold gathers in algae. I think it can be used as a new collection method." I would like to successfully develop this technology and connect it to the circulation of resources with the result of exceeding."
Why focus on “hot springs”?
"Gold" is mainly contained in magma deep underground.
The groundwater around the magma has a temperature of several hundred degrees Celsius, and after gold melts into this hot water, it rises to the surface over a long period of time.
After that, it cools down and solidifies, and it is thought to be a vein of "gold", and it is common to mine it in the mountains and take it out.
In the past, a large amount of gold was mined at the Sado Gold Mine in Niigata Prefecture and the Konomai Mine in Hokkaido. It is
Currently, the Hishikari Mine in Kagoshima Prefecture is the only mine in Japan that continues to operate on a commercial scale, and it produces approximately 4 tons of gold annually.
The research team thought, ``If it is dissolved in high-temperature groundwater, it may also be included in hot springs,'' and tried a new method at Tamagawa Onsen in Semboku City, Akita Prefecture.
The reason why Tamagawa Onsen was chosen as the location for the experiment is because of the idea that gold dissolves more easily at high temperatures and strong acidity. It is said to be a top-class strong acidity.
Collecting gold with algae?
The research team focused on the research results of a university announced several decades ago in order to efficiently extract the "gold" that melted into hot springs.
It was revealed that cyanobacteria, a type of algae, have the property of adsorbing gold.
IHI Senior Researcher Yasuyuki Fukushima, who was involved in the development, thought, "By using this 'algae', we can create a material that efficiently absorbs 'gold'," and explored the possibilities of cyanobacteria. rice field.
Fukushima's senior researcher assumed that the "gold" dissolved in the hot water mainly combined with chlorine and existed in the form of a compound. succeeded in separating the
Convinced that it would be possible to recover "gold" by applying this, the "cyanobacteria" were cultivated for about half a year, then chemically powdered, dried, and processed into sheets.
We have developed a method that is different from conventional mining.
In addition to this, the research team also conducted an experiment to extract gold by installing sheets of cyanobacteria using unmanned submersibles in the deep sea, around 700 meters deep, off the coast of Aogashima, Tokyo, where high-temperature hot water is blowing out. going.
The rocks around the hot water spout contain an average of 17 grams of "gold" per ton, so next year we will collect the sheet and confirm the results.