Oxidation peroxide vs bleach vs chlorine gas

[Jpenzo]

First off I'm a noob to this.

I'm definitely not well educated in chemistry. I understand enough to know I don't know enough to just try stuff.

Could someone please give me a brief explanation of why adding sodium hypochlorite, hydrogen peroxide, or chlorine gas to HCI is different in the end result? Obviously having different by products from other ingredients, could one not be substituted for the other if the byproducts didn't interfere? That being said bubbling chlorine gas with a fine dispersion of bubbles to maximize surface area of the gas being introduced to the solution seems to me would have the least byproducts and maximum effectiveness.

Please forgive my ignorance and forum etiquette. I'm new to forums and PGM recovery.

When I say brief I would be happy with a link pointing to an article or any small amount information to point me in the right direction. I'm not afraid to do the research, I just don't know where to start on that question without diving head first in to learning chemistry.

 

[anachronism]

I cannot answer everything you asked however:

Sodium Hypochlorite works as a chlorine gas generator in the solution so effectively the same gold dissolving chemistry is happening as bubbling the pure Chlorine gas through HCl.

Hydrogen peroxide works as an oxidant. I'm not sure of the exact chemistry however I believe that in sufficient quantity it can react with the HCL to produce some Chlorine therefore producing the same end result but by a different means.

Low amounts of peroxide are used with HCl in order to begin a Copper Chloride leach also known as Acid/Peroxide or AP which is used to dissolve base copper and metals from behind gold plating.

I'm sure someone will provide better explanations shortly.

Jon

 

[butcher]

sodium hypochlorite is a basic solution (opposite of an acid) and will begin to neutralize acid making salts of the acid.
2Au + 6HCl +3NaClO --> 2AuCl3 + 3NaCl + 3H2O

Concentrated H2O2 basically breaks down to oxygen and water.
2Au + 6HCl + 3H2O2 --> 2AuCl3 + 6H2O

Both of these oxidizers work best when gold is fine.

 

[Jpenzo]

Thank you both for the response.

Would I be right to assume bubbling chlorine in HCI would be the most efficient method of dissolving PGM with the least amount of waste product? Not counting the source of the gas.

It seems everyone uses a different method at different times. I know I need to study the actual reactions. This assumption is just kind of off the top of my head.

 

[butcher]

Chlorinated solutions will dissolve fine gold powders or flakes, but is not effective for thicker pieces or where a stronger oxidizer is needed, like aqua regia or a nitrate salt...

Chlorine gas works best at higher temperatures but in a solution, at those temperatures, most of the gas is lost to the environment, and not working to react with gold.

Cooler temperature will keep more chlorine gas in solution, while heat can assist in how fast the reaction proceeds (two-edged sword).

bubbling chlorine gas would not form sodium salts and increased acid consumption as would the bleach with its sodium hydroxide component to make it basic and to keep the chlorine gas dissolved in the water.

It would not dilute the solution as the concentrated hydrogen peroxide would (normally not a problem).

While chlorinated solutions will dissolve fine gold powders and some PGM powders, it is not that good of a choice for much more than very finely divided particles of some of these metals.

 

[Jpenzo]

That makes sense. I really appreciate you taking the time to explain it to me. I was thinking but just not far enough. I couldn't see the reason for not just using Cl gas. It seemed like a simplified way to achieve the same goal. I can see how keeping in the solution for a extended period of time would be a problem.

Again thank you for the help.

 

[butcher]

You can generate chlorine gas fairly easily with a little lab setup and bubble it in, but it is really easy and convenient to generate the chlorine directly in the solution using H2O2 or NaClO...

 

[rickzeien]

You can generate chlorine gas fairly easily with a little lab setup and bubble it in, but it is really easy and convenient to generate the chlorine directly in the solution using H2O2 or NaClO...

Could you elaborate on the setup. And a setup to generate So2 to drop gold from AR

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[butcher]

Burning sulfur in oxygen will produce SO2.
H2SO4 + Na2S2O5 → 2 SO2 + Na2SO3 + H2O



Preparation of sulfur dioxide from copper shavings and sulfuric acid.



Sulfur dioxide can be generated by the action of ordinary concentrated sulfuric acid on sodium, potassium, calcium sulfite (or bisulfite):
Preparation of sulfur dioxide from sodium sulfite and sulfuric acid


Sodium sulfite or bisulfite is placed in the bottom of the 300 ml Erlenmeyer flask of the apparatus. The dropping-funnel is filled with dilute sulfuric acid, made by pouring one volume of concentrated sulfuric acid into an equal volume of water and cooling the mixture.
A glass apparatus for the preparation of sulfur dioxide

A glass apparatus for the preparation of sulfur dioxide

The glass elbow is connected with a gas washing-bottle containing concentrated sulfuric acid, and the dry gas is collected by displacement in two or three empty cylinders. On allowing the dilute sulfuric acid to drop slowly upon the sodium acid sulfite, a very regular evolution of sulfur dioxide is obtained.

Instead of using an inorganic acid for the evolution of sulfur dioxide, it is convenient to use sodium hydrogen sulfate (NaHSO4). A mixture of equivalent quantities of the respective salts in powder gives, when wetted with water, a regular stream of the sulfur dioxide gas, which will be free from the impurities usually derived from the use of an acid.
https://goldrefiningforum.com/phpBB3/viewtopic.php?t=17070
H2SO4 + Na2S2O5 → 2 SO2 + Na2SO3 + H2O
https://en.wikipedia.org/wiki/Kipp%27s_apparatus

https://chem-guide.blogspot.com/2010/04/preparation-of-halogen.html
https://chem-guide.blogspot.com/2010/04/preparation-of-halogen.html

 

[rickzeien]

Thanks. This is awesome!

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