[WorkingWithPGMs]

Hello,
Shade tree, hobbyist gold refiner here.

I'm using -200 powdered Zinc as per imprecise instructions, to adsorb (right word?)
gold from a base solution.

How much gold per gram of added zinc will the zinc hold? 

My goal is to not waste powdered zinc.  I've been told it is now on the Consumer Protection list as a 1# per calendar year restricted basis in this fine grind particle size.

All assistance is appreciated.

[Fleaker]

Cementation isn't the same as ab/adsorption.

It's reduction.

try http://www.goldrefiningforum.com

[WorkingWithPGMs]

Thanks for your reply, especially since you are the only one who did.  That's better than that forum you provided the url to.  That is one big clique over there, and no one responds.

If I'm using the wrong words, I'm sorry.  Do you know what it is I'm trying to say?
Do you have the answer to my question as to how much zinc it takes to pull gold out of solution?

I'd sure appreciate it.

[zxt]

Thanks for your reply, especially since you are the only one who did.  That's better than that forum you provided the url to.  That is one big clique over there, and no one responds.

If I'm using the wrong words, I'm sorry.  Do you know what it is I'm trying to say?
Do you have the answer to my question as to how much zinc it takes to pull gold out of solution?

I'd sure appreciate it.

Caculate upon this equilibrium:
            Au²⁺+Zn :rarrow:Zn²⁺+Au

[Fleaker]

That equation is incorrect.

Using zinc for reducing gold out from gold bearing solutions (be they cyanide or acidic) is a method to be used only for recovering gold, not for refining it. To refine it requires a selective precipitant (i.e. sodium metabisulfite, oxalic acid, etc.) Zinc will reduce gold, copper, silver, lead, and a variety of other metals above it on the reduction table.

Realistically, if you don't want to waste zinc powder (an exceedingly cheap resource which you should have no issue obtaining from numerous suppliers, CPSC silliness or not), you will only use it for pure gold solutions, so that all of the available zinc will go to reducing Au⁺³ to Au⁰. You see, if you have a solution containing quite some copper and other metals, and perhaps only a gram of gold per liter, it is ill-advised to use zinc, because then you're left with many base metals that need to be dissolved away before you're left with the gold. Much better is to use a selective precipitant, or perhaps solvent extraction (i.e. dibutyl carbitol) to obtain the values and keep costs down.


I find it interesting that you don't like that forum, as it is the preeminent resource for precious metals refining, recovery, and handling on the internet. I'm keen to hear why it's such a clique. The only thing with that place is that they don't like people who refuse to read what has been written...and your question has been answered there.

[WorkingWithPGMs]

Thank you zxt and Fleaker both. I have a better understanding now.  As for your concerns re: contaminating base metals, i personally address that by first a thorough rinsing of the ppt, prior follow-on H2SO4 rinse.  You asked about the clique I spoke of on that other forum.  I've observed behaviors from Harold which are dismissive, arrogant, and repetitively monotonous, but which always result in backslapping and kudos from the other 5 main players.  Obviously you have not, scoldings which are undeserved, and the whole attitude of the place change from the early days.  If you believe my question has been answered there as to the ratio of zinc to au, please be so kind as to quote it.  I'd like to read it for myself. There is science and there is arm waving and story telling.  I prefer the science.  Stories are for kiddies at bedtime.  If that is the pre-eminent site and they are compared to what is available here, this forum wins the gold medal. Thanks everyone.