New Gold Extraction Method Involving Corn Starch

Article taken from PopSci, see original here.

I have an interest in gold extraction because I did a bunch of cyanide leaches for that very purpose, while working as a chemist. I’ve read about the various environmental concerns of flooding underground chambers with cyanide to extract gold in-situ, and about the odd accident involving cyanide that occurs at CIP plants. A new method for gold extraction (excluding cyanide) would be well received news.

This article — reproduced below — however, just seems to be grossly overstating the importance of an accidental (albeit awesome) discovery. Without knowing too much about it, I’m sure that there will be a raft of problems involving the industrialization of a process like this, and it’s going to take decades (if ever) for something like this to work. The paper talks about second-sphere coordination chemistry which is highly complex and is going to depend on minute variations in the concentration of species in solution.

It’s frustrating that the article makes it seem like the applications of a really awesome discovery in pure science are mere moments away, rather than explaining why a discovery like this is awesome and encouraging peoples’ interest in supporting research on it.

I appreciate the discovery on its merits and it bothers me that journalists hype this sort of thing; then get frustrated and lose interest in it when it doesn’t show immediate commercial applications. I read just recently about how the science minister of Canada made statements about how the National Research Council isn’t going to pursue projects with immediate commercial applications and it makes me sad. Little curiosities like this can grow into amazing large-scale processes with a bit of support, but a lack of funding threatens to take that away. A public conditioned to a perpetual hype/fatigue cycle are not going to appreciate the merits of pure science and will keep voting in science ministers that lack credibility.


Cornstarch Replaces Cyanide In Clean New gold Extraction Method

Scientists accidentally discover a new way to isolate gold that is much safer than existing processes, which use toxic cyanide.

By Rebecca Boyle


Gold, precious forever but especially lately, is a tricky metal. Bound up in consumer electronics, jewelry and the ores that it comes from, gold is difficult to extract, and most modern processes do it with a highly toxic combination of cyanide salts. The cyanide leaches the gold out, but the cyanide can seep into the ground, causing environmental problems and posing threats to human health.

Researchers at Northwestern University recently stumbled upon a solution that uses cornstarch instead. It involves some complex chemistry, but it’s cheap, biologically friendly and nasty-ingredient-free.

Led by Sir Fraser Stoddart, a chemistry professor at Northwestern, the team discovered this method by accident when looking for something else. A postdoc named Zhichang Liu was trying to make three-dimensional cubes out of gold and starch, aiming to use them as storage containers for gases and small molecules. But a liquid mixture of dissolved gold-bromide salts and a starch-derived sugar didn’t form cubes, it formed needles. This was strange, so the team decided to try to replicate it and tested different forms of sugars.

Alpha-cyclodextrin, a cyclic starch fragment with six glucose molecules, is the best way to isolate gold, they found. “Zhichang stumbled on a piece of magic for isolating gold from anything in a green way,” Stoddart says in a statement. The spontaneous bundle of needles is made of thousands of nanowires, each 1.3 nanometers in diameter, which contain a charged gold atom inside four bromine atoms.

The interaction between the starch fragment and the gold allows the precious metal to be selectively recovered from other materials, including platinum, palladium and others. The researchers already developed a process to isolate gold from scraps, and they hope this will lead to an environmentally friendly, cheap way to recover gold from anything. The research is published in Nature Communications.