If you’ve ever seen pictures of the California Gold Rush, you might remember images of men sitting by a river pouring water through a grated pan. If they got lucky, they might find a golden nugget or two. Most such prospectors came back unsuccessful, so nowadays we typically get gold from mining for ore instead. Mining for gold is expensive and uses a lot of material to make a small amount of gold. That could soon change. A team of chemists from Switzerland has developed a tool that can capture individual gold ions from water sources. It functions almost like a microscopic gold-pan.
The tool is called a type of MOF, or Metal Organic Framework. In a MOF, a small set of organic molecules surround a metal atom, in this case, iron, like a cage. This new MOF is exposed to a polymer, a long chain of repeating molecular units, and the MOF causes the polymer to swell up into a porous structure. The polymer then grabs gold ions from water and adds an extra electron to form metallic gold. Unable to leave, the metallic gold is then stuck in the polymer. It’s almost like the MOF works as a pan fishing out a single atom of gold at a time, instead of a larger rarer nugget.
The researchers found that each combined gram of polymer and MOF put into the solution could remove almost one gram of gold before becoming saturated. They then tested their new material in a variety of water sources, including water used to extract metals from old or broken electronic devices, rivers near mining operations, and wastewater shown to have high levels of gold. They were able to remove between 90 and 99 percent of the gold in each solution, often in as little as two minutes. Furthermore, the material didn’t remove many non-gold metals in the water and the gold had a purity of 23.9 Karats. The researchers hope to further refine their material to remove gold from the ocean, which is particularly challenging because the ocean has very low levels of gold and very high levels of other salts.
Managing Correspondent: Emily Kerr