Acid Peroxide Process Information Thread Q & A's

[Kubik_Rubik]

Hello, I am extremely grateful for this forum.
I have limited access to pure nitric acid, so I save it for silver recovery. I've already used AP solution to process gold fingers, but I have a lot of relay contacts that are on a piece of copper or brass base. Many of the contacts also contain palladium. Because I would like to save nitric acid for processing the contacts themselves, can I use an AP solution to remove the base metals? I would just use a little H2O2 and a bubbler. Is there a danger of dissolving silver and palladium in the solution? I read a lot about AP, but I didn't come across this.
Thank you very much for the advice.

 

[Martijn]

Here is a recent thread about contact points:
https://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=29529&p=310631&hilit=Silver+Contact+points#p310393

 

[Kubik_Rubik]

Thank you. I missed that thread. So I'll continue there.

 

[Outlaw72]

Once your AP is used up, I see most people add in a piece of copper to cement out any PMs that might be leftover or trapped in solution and as a first step in waste treatment. Do most people save up this cemented out material, and process it again with AP to ensure gold and other PMs haven't been left behind? Just curious as I have never done these steps yet, but plan to in the future once I feel comfortable with the processes.

 

[Martijn]

Yes they do once they have 'enough' worth processing. That's the reason we have a stockpot. We recover and stock our missed traces of pm in there. The moment when to do it is a personal choice. And how patient you are :wink:

AP can be reused for ever. If 'used up', just add a splash of HCL and air. Eventually you will have more than you need.

Treating it like in the stockpot can cement out some Pd that does dissolve in AP. The 'AP' or Cu2Cl in the stockpot can also redissolve some Pd. Silver traces i'm not sure about.
But as far as i know, no other PM's will dissolve in AP. Make sure there is not too much free HCL left. It will consume more copper first.
Stockpot black powders can contain traces of gold and PGM's.

 

[Outlaw72]

Thank you, I couldn't find anything on the leftover material, probably due to the fact that trained refiners don't lose much if any gold in there waste solutions. I'm just trying to find as much information on AP as possible because it's probably the method I'll be using once I feel comfortable with everything. Another question I'm having a hard time finding an answer to is, what happens if too much peroxide is added. I have seen in different places, and posts people using a 3:1 ratio, some a few drops, and others a splash. If too much was used, you would lose gold in solution?

 

[Shark]

To much peroxide and AP (Copper II Chloride) will start dissolving gold. With an excess of copper the gold will cement back out over and over until the solution is saturated or the base metals are fully dissolved.

The real reason you don't need an excess of peroxide is that your not using acid and peroxide as a chemical mixture. Your using the two to create another (single) chemical, copper II chloride, which is the actual etchant. AP can be created without the peroxide, it just takes a little bit longer to do as the hydrochloric acid must then get its oxygen from the surrounding air.

 

[Outlaw72]

Thank you guys for the quick responses, part of my learning is reading about the issues others are coming across and learning to fix them before ever starting my own processes. That way I'll have it in my notes if it should happen to me. Reading material like Hoke has it's uses for me, but to be honest a lot of it doesn't stick because I haven't seen these reactions and processes in person, and constantly need to revisit and reread parts of the book to remember certain things she explains. I have found this forum very useful as I move towards my attempt at a new hobby that I have a lot of interest in.

 

[Martijn]

Leaving copper (cemented or filings) wet and open to air will create alot of copper oxide which will dissolve fast in HCL. Quick way to get it started. No H2O2 needed.

 

[dpgold]

The purpose of this thread is to begin to consolidate the vast amount of questions and answers related to the Acid Peroxide (aka AP) recovery process.

First and foremost, the name for the process, Acid Peroxide is a misnomer as the active ingredient is actually copper II chloride (CuCl2), so it should have been called the Copper II Chloride Etching process. Once the copper II chloride (C2C :idea: ) is formed it is reusable indefinitely if you take care not to foul the solution. Once formed all you need is air, HCl, and water to keep things going forever using the same solution. Your only problem will be the ever increasing volume of the C2C solution and it's proper disposal.

Secondly, C2C should be used primarily to remove copper from gold bearing scrap before attempting to digest the gold. If the plated scrap is magnetic (kovar or iron/steel) then AP (C2C) is not the process to use.

The last key note is that if you use too much hydrogen peroxide (3%) to initally generate your copper II chloride you may dissolve some of your gold into solution. If you think more is better and add too much too quickly or use too high of a concentration of hydrogen peroxide you will dissolve gold. The peroxide is a catalyst for the reaction, not the active ingredient. If you do this then simply keep using your AP as directed without adding any peroxide until it becomes saturated with copper and the gold will cement out on it's own. There is no need to add any other precipitants to the solution and doing so will foul the solution.

If you haven't read the Copper II Chloride etchant document on my website in the documents section now is the time to do so. You'll be light years ahead of the game as to what to look for and what the various colors of the solution indicate. You'll also have all the chemistry information you could want on the topic.

Now to the consolidation of previous Q&A's on the topic:

• Learning AP: AP Acquaintance Test Setup
• AP Common Facts: Acid Peroxide Notes
• AP Q&A: Acid Peroxide Help
  • AP Cleaning Foils: Gray Powder in Foils
• AP Waste: Dealing with Excess AP
• Summary of AP Clean up

If you are a visual learner then you can watch the Acid Peroxide videos for free on my website or you can buy the full length DVD: Processing Finger Boards with Acid Peroxide at my web store, it's the first item on the list.

This post is a work in progress and will be updated as I have free time to consolidate the information scattered across the forum.

Steve

Hi I am confused about this, is AP HCL plus H2O2 ? If so peroxide is H2O2 ? Where does the CuCl2 come from? I am a beginner, thanks. Also if somehow I added too much 3 percent H2O2 and gold will cement on copper how do I correct this problem?

 

[Yggdrasil]

The AP process is not an Acid Peroxide leach actually.
It somehow was named so because most started this leach by adding a cap or two with peroxide to HCl
to create some Copper (I) Chloride to jump start the process, a Copper Chloride leach which it actually is.
In fact HCl do not dissolve copper by itself.
But Copper II Chloride etch the Copper to Copper (I) Chloride which in turn dissolves in HCl creating more Copper II Chloride and so on.
If you, as Martijn, says just sprinkle some HCL onto Copper and let it sit for a few days/weeks until its green,
you can put it into HCl and you instantly have Copper2Chloride leach.
Or wait until the Oxygen in the HCl reacts with the Copper.
Most of us don't have that kind patience, so we just use an air bubbler.

 

[Martijn]

It is confusing indeed.
We use the term Acid Peroxide for the cupric chloride leach, also used in etching copper traces in circuit boards.
It is in fact the cupric chloride that does the work.
Hydrogen peroxide, H2O2, is added to hydrochloric acid, HCl, to start the first digestion of copper into cuprous chloride, CuCl1.
Then the cuprous chloride reacts with oxygen and free HCl to form CuCl2.
H2O2 or air can be used to supply the solution with oxygen for this conversion.
When CuCl2 reacts with copper, it creates CuCl1. And it starts over again.

Please use the search function from this site to look up info. Trust info from older members in general.
Use google to search for chemical info and names. Wikipedia for elements and compounds is what I use most.

The questions you ask indicate you should stop experimenting and study what you are doing. Then present your plan here for us to review.

Martijn.