Researchers at Northwestern University have discovered a way to extract gold that uses cornstarch instead of a conventional, cyanide-based method.
Everybody seems to have gold fever these days, and with shows like Jungle Gold, Gold Rush, Yukon Gold and Bering Sea Gold filling the tv time slots, it isn't surprising. What sets these programs apart from the real world is that most gold extraction processes today aren't based around washing and panning dirt, but rather use toxic chemical processes involving cyanide salts. The cyanide leeches the gold out of ores, but as a side effect, they can seep into the ground posing threats both to the environment and to human health.
Researchers at Northwestern University have discovered that cornstarch can do the same thing as cyanide salts, while being both cheaper and environmentally friendly. The cornstarch process involves complex chemistry and was discovered by accident while lead researcher Sir Fraser Stoddart, and his team, were looking for something else. Zhichang Liu, a postdoc at the university, was trying to build storage cubes for gases and various molecules using a combination of gold and cornstarch, but when he discovered that his experiment yielded needles, and not cubes, the team decided to investigate.
Sir Fraser Stoddart
The team found that the best way to isolate gold involves a cyclic starch fragment called alpha-cyclodextrin. “Zhichang stumbled on a piece of magic for isolating gold from anything in a green way,” said Stoddart. The needles, the team discovered, was composed of thousands of nanowires of diameter 1.3nm, all containing a structure of one gold atom surrounded by four bromine atoms. The technique can be used to extract gold in similar needle structures from virtually any material.