EIACP (PC-RP) on Environmental Problems of Mining

Date: May 16, 2013

Gold mining has often been associated with serious environmental issues. Miners often use highly poisonous cyanides to extract the precious metal, which can lead to the contamination of the environment. Now, though, researchers have found a way to mine gold that's both environmentally friendly and cheap--by using cornstarch.

The new method that researchers developed has the potential to extract gold from crude sources while leaving behind other metals that are often found together with crude gold. In addition to mining, though, the process could potentially be used to snag gold from consumer electronic waste, which uses small amounts of gold in its creation.

Cornstarch, though, isn't the only ingredient that they're using for this new method--though it is part of it. Zhichang Liu, a postdoctoral fellow and first author of the paper, wanted to make an extended, three-dimensional cubic structure that could be used to store gases and small molecules through the use of solutions. In order to accomplish this, Liu took two test tubes containing aqueous solutions--one made of the starch-derived alpha-cyclodextrin and the other made of a dissolved gold salt, called aurate. Liu then mixed them together in a beaker at room temperature.

Unfortunately, the solutions didn't produce the cubes that Liu hoped for. Instead, the experiment produced small needles that formed rapidly after the two solutions were mixed. That didn't deter Liu, though. He examined the composition of the needles in order to find out exactly what his solutions produced.

"Nature decided otherwise," said Fraser Stoddart, senior author of the paper, in a news release. "The needles, composed of straw-like bundles of supramolecular wires, emerged from the mixed solutions in less than a minute."

Liu wasn't done yet, though. He then screened six different complexes, each combined with aqueous solutions of potassium tetrabromaurate or potassium tetrachloroaurate. In the end, he discovered a solution that isolated gold the best of all--alpha-cyclodextrin, which is a cyclic starch fragment composed of six glucose units.

"The elimination of cyanide from the gold industry is of the utmost importance environmentally," said Stoddart in a news release. "We have replaced nasty reagents with cheap, biologically friendly material derived from starch."

So exactly how environmentally friendly is this new solution? It's "relatively environmentally benign," according to Stoddart. At the very least, it's probably better than cyanide. The findings could certainly help the gold mining industry, and make it just a bit more benign to the surrounding environment.

The findings are published in the journal Nature Communications.

(Source: http://www.scienceworldreport.com/)