Gold mining is a controversial business as it uses cyanide to extract gold from the raw ore and discharges the waste cyanide into a tailing pond or spent heap. If mishandled the cyanide can seep into the ground, causing environmental problems and posing threats to human.
Zhichang Liu, a postdoctoral fellow at Northwestern University, USA, has stumbled upon a solution that uses cornstarch to replace cyanide in the leaching process. It involves some complex chemistry, but it’s cheap, biologically friendly and nasty-ingredient-free.
Before the finding, Liu was trying to make an extended, three-dimensional cubic structure, which could be used to store gases and small molecules. He mixed starch-derived alpha-cyclodextrin with a dissolved gold salt, called aurate, in a beaker at room temperature. Unexpectedly, he obtained needles, which formed rapidly upon mixing the two solutions. Firstly, disappointed with the result. He quickly turned excited and would like to learn more the needle.
After more tests, it was discovered that alpha-cyclodextrin, a cyclic starch fragment composed of six glucose units, was best at isolating gold from the solution. But not only is this process a lot less toxic than the cyanide leaching process, it also appears to be more efficient at isolating gold.