Japan is rich in water-soluble natural gas, which exists underground in the state of methane dissolved in salt water called "brine".About 2,000 times as much iodine as seawater is dissolved as iodide ions in this brackish water, and "iodide ion oxidizing bacteria" that oxidize iodide ions to produce iodine inhabit.On the other hand, it is known that a mixed solution of iodine and iodide ion dissolves gold.

　The research team conceived the leaching of gold from gold ore using the same bacterium.Eight kinds of iodide ion-oxidizing bacterial strains isolated from irrigation were fed with iodide ions and a nutrient source, and cultured at 8 ° C for 0.26 days together with gold ore (gold grade 3.3 wt%, ore amount in medium 30 w / v%). bottom.As a result, the bacterium oxidized a part of the iodide ion to iodine, and triiodide ion was generated from the iodide ion and iodine, and the gold in the ore was dissolved as diiodide gold acid ion.For three of these strains, all the gold contained in the ore was leached out, and using the best strain, all the gold was successfully leached out of the ore in 30 days.

　This is expected to establish a method that can economically leach gold with a small environmental load by using microorganisms and iodide ions that originally exist underground.In addition, it may be possible to develop a method for injecting microorganisms and iodide ions into underground gold ore bodies through wells without mining ore, and then leaching gold underground and recovering it to the ground.

Paper information:[Scientific Reports] Gold Dissolution from Ore with Iodide-Oxidising Bacteria