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Cornstarch Replaces Cyanide

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I've seen this pop up in the news here and there.Using cornstarch to isolate gold.Has anyone had any experience with this?Does anyone have the ability or knowhow to test this?Came across this article today and started thinking about it again.



Cornstarch Replaces Cyanide In Clean New Gold Extraction Method

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.


Read more here.




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Why is bromine considered green and HCN isn't?

If bromine is "green" (actually a brown liquid at room temperature), then why not its more active cousin halogens like chlorine and flourine?

From the article:

"We have managed (see Fig. 8 and Methods) to convert two scrap gold-bearing alloys containing 58% wt of Au and 42% wt of other metals (Zn, Cu and Ag) into HAuBr4 by dissolving them with a mixture of concentrated HBr and HNO3 as the etchant solution."

At the bottom of the cited article is a great comment by Melvyn Lintern especially re: aqua regia (HCl and HNO3).


Did anyone read the editorial policy for Nature Communications? I did.

Nuf said.

However thanks for the interesting post.


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Hi I am new to all of this. would be thankful for any help.

I have tried asking around and cant find any help. One company who test the stuff said that its loaded with microns but did not say what the other stuff was or how to refine it.

I would love to know more and if this would be able to remove micron gold from very heavy black beach sands and cons from a sluice that are also micron sized, here in Australia there is heavy minerals that make it extremely hard to get down to the gold. Of late I have been ending up with a substance at the end that looks like icing sugar that has not dissolved in water white silver in appearance. With a few tiny specks in it of gold but seems the same weight. Tried heating it up to see if its mercury but it stayed the same. No one can tell me what this is. Out of a 20 ltr bucket i end up with about 5 table spoons of this and 20 bits that i cant seperate. I am sure there is also gold microns that i can not see in there also. how would i be able to use the starch to get the Gold out. Thank you 

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