Acid Peroxide Process Information Thread Q & A's

[robertpdickson]

Jim,

But it is the best way to go correct? Or at least the most likely not foul the reaction? I understand it is a bit more costly but it seems to be dog gone effective.

I believe Hoke recommends this as the first step to cleaning dirty scrap.

Thanks, Robert

 

[jimdoc]

Jim,

But it is the best way to go correct? Or at least the most likely not foul the reaction? I understand it is a bit more costly but it seems to be dog gone effective.

I believe Hoke recommends this as the first step to cleaning dirty scrap.

Thanks, Robert

The first step should be to remove as many base metals as you can, without the precious metals going into solution with the base metals. Nitric will put palladium and silver with your base metals. It depends on what you are working with I suppose.

Jim

 

[Geo]

AP is a "work around" method. that doesnt make it any more or any less effective than any other. this has been discussed tirelessly on the forum, the pros and cons of AP as apposed to other methods. your particular outcome may be different due to many different factors. type of chemicals, type of equipment, level of experience, even the weather plays a role.when you use nitric acid to reclaim gold foils, the nitric and the copper is consumed and converted to mostly copper nitrate. when AP is used the hcl and copper is consumed and converted to copper chloride.copper chloride when in the presence of oxygen, will etch or dissolve copper fairly quickly. when you create copper nitrate, thats pretty much the end of the line for its usefulness. copper chloride can be used over and over again which makes it more economical still seeing as hcl is SO much cheaper than nitric acid. theres much more to the back and forth but the main thing in it all is (1) AP is cheaper and can be re-used (2) nitric is much faster.

 

[robertpdickson]

Okay, thanks all. That pretty much clears up the mystery to me. I am not years upon years a seasoned gold refiner so I may not understand how to work with AP effectively or efficiently yet. Nitric (although more expensive) might be the newbie's safe bet and the reusability of AP does have its benefits as well.

Again, this is a great forum and help is fast and good on here!

 

[Geo]

Robert, that is not true. nitric acid is very dangerous and very harmful to your health. when you dissolve metal with nitric acid, nitrogen dioxide (NO2) is evolved. if you inhale this in any concentration, it will form nitric acid in your lungs by mixing with the water vapor there. nitric acid kills living cells on contact. your lungs never, NEVER, heal from being damaged by it. it is a cumulative effect, it destroys your lungs a little at a time until you are like me. i am 48 and have never smoked a cigarette in my life but i suffer from COPD caused by inhaling NO2 fumes while making nitric acid 20 years ago. now instead of looking forward to watching my grandchildren grow up, im discussing with my doctor whether or not ill make a good lung transplant recipient. nitric acid IS NOT the safest and best for beginners. besides cyanide, i cant think of a more dangerous chemical for a newbie to try and work with.

i apologize for being so graphic, but i just want you to understand what kind of danger you are putting yourself and perhaps those around you in by using nitric acid.

 

[xALmoN]

Just a quick question.

With acid Cu2+ etching, my impression is that this system is specially selective towards copper only and will not etch anything else (but what about the free acid?)

Am I right about this?

 

[butcher]

In the copper II chloride leached base metals lower in reactivity series will go into solution as chlorides producing copper I chloride, in the electronic scrap like with solder the tin will go into solution and lead chloride will precipitate, as will silver chloride.

It works best if specifically used for copper as this way it is re-useable and just generates more copper II chloride, but it will leach other metals into solution.

 

[xALmoN]

Steel does not dissolve though, or does it? i remember seeing a few posts that steel pins do not dissolve. is that because the acid concentration is high? 2M isn't all that high though, imo. Is 2M considered conc or dilute?

I guess, a pretreatment with HCl before AP will be appropriate if other base metal contaminates are suspected to be present. Would ferric chloride affect the solution in any way other than potentially binding up Cl-? Though I dont think there's any binding up of Cl- as the salts are fully soluble.

 

[butcher]

If iron metal is added to a solution of copper II chloride, the iron will dissolve (or iron from the steel), this will form a solution of iron chloride, the copper will precipitate from solution as copper I chloride and or copper powder

Copper and iron can also be in this solution at the same time.

Iron chloride can also dissolve copper forming an iron hydroxide with heating.

Iron chloride cannot be rejuvenated like copper chloride can.

Steel or kovar in pins can be leached with acid peroxide, but if much iron is involved you cannot reuse the solution long, as eventually you end up with an iron chloride solution and not a copper chloride solution (which can be rejuvenated and reused if kept healthy).

Read the documents on Laser Steve's web site for a better understanding of this leaching process.

 

[xALmoN]

Roger that.

Those were just some preliminary questions i had to get out of the way before i continued.

 

[butcher]

A google search and reading about the reactivity series of metals is very helpul in the chemistry we use.

http://www.google.com/#sclient=psy-ab&hl=en&site=&source=hp&q=reactivity+series+of+metals+&btnK=Google+Search&rlz=1R2RNQN_enUS457&oq=reactivity+series+of+metals+&gs_l=hp.12...10610.10610.1.11578.1.1.0.0.0.0.0.0..0.0.les%3B..0.0...1c.dovqlJDh174&psj=1&bav=on.2,or.r_gc.r_pw.&fp=243757dd2ec462e8&bpcl=35243188&biw=1024&bih=539

 

[JesseSShaw]

Guys, this whole AP process seems to be a huge waste of time and materials. Currently I'm stripping gold foil from cpus using straight Nitric acid and it works fine each and everytime. Whenever I introduce HCL and peroxide or Cl it blows up (not literally) into a green nasty solution with cemented everything in the sludge.

Please tell if I am crazy but is this AP process here not the best way to go? Not slamming anyone or trying to be rude.....its frustrating. I have a good chem background but I believe I am not good enough as some on here to use the AP process. Just looking for validation.

Thanks all and gold be with you.

Nitric costs a lot more, and is harder for people to find in some areas.

Jim

Just some information I posted earlier in another thread. Using nitric acid is of course an alternative. The decision is easier for each individual's circumstances with the proper information. I use nitric acid because this AP method is too much for me to bother with. I may try this method at a later time but for now it just seems like too much to deal with as robertpdickson suggested. Then again, I have learned long ago how to easily make and safely handle a nitric acid concentrate.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=16420&start=20#p180610

 

[lazersteve]

Acid Peroxide (AP) is one of many 'tools' in the refiners box. There are several situations where AP is the best tool, there are others where it is not. Nitric acid has drawbacks of it's own and is difficult to remove once you use too much, a common occurrence with nitric acid users. I use AP and nitric acid both in my refining, as well as many other useful reagents. Many people have limited resources and/or no access to nitric acid and choose AP for this reason. Others dislike the deadly BFRC (big frigging red cloud) and prefer to use chlorine.

If your AP reaction went haywire you added too much peroxide at one time. Nitric acid will also boil over if you are too heavy handed with it or apply it to finely divide material. Regardless of whether you use AP, Nitric acid, or any other oxidizer, you must observe proper technique to get the desired results.

In my opinion AP is a great tool for working with Palladium scrap as well as many other scrap types. Choose your recovery and refining processes based upon the scrap type, as no reagent is a 'one size fits all' solution.

Steve

 

[JesseSShaw]

Many people have limited resources and/or no access to nitric acid and choose AP for this reason. Others dislike the deadly BFRC (big frigging red cloud) and prefer to use chlorine.

That is why I posted the information that I did. Just wanted to share that it isn't difficult to make nitric acid provided one understands the process and adheres to the safety precautions. Knowing the dangers of working with the many corrosive and toxic chemicals and compounds being used for PM recovery is a necessity anyways. Sometimes it is better to remove steps to avoid problematic situations. There are more steps in using the AP process than in using nitric acid from what I can see. Therefore, there are more places where something can go wrong. As you said though, the application determines the process. I agree completely that the big red cloud of nitrogen dioxide is scary. It's the big invisible clouds of toxic gas such as chlorine that scare me even more lol.

 

[butcher]

Sometimes there are more than one way to do things, with nitric acid it is like a sledge hammer it does a good job, but it can have its draw backs, cost, deadly fumes, and if tin is involved a mess.

Copper II chloride leach (HCl acid peroxide), is also a wonderful tool, it is slower, works best for dissolving copper, it is a smaller hammer in our tool box, but sometimes the smaller hammer can be the best tool for the job, but if you learn to use it properly you will find in a very useful tool.

I cannot say one tool is better than the other, but I may pick one tool over the other for certain jobs, and which tool I pick is normally determined, by which tool I feel is best for the job at hand.

 

[kkmonte]

Many people have limited resources and/or no access to nitric acid and choose AP for this reason. Others dislike the deadly BFRC (big frigging red cloud) and prefer to use chlorine.

It's the big invisible clouds of toxic gas such as chlorine that scare me even more lol.

It's not invisible to the nose! You'll know when you add too much bleach! That is the plus with using the AP solution, both HCL and CL fumes are very noticeable. I haven't worked with Nitric yet, but I know NOX fume breathing is cumulative. (Not sure if its the same with HCL or CL). Like you said, there are alot of deadly things we use and need to be careful with using them all. Most of them can kill you if used incorrectly, some faster then others. To each its own I guess.

 

[JesseSShaw]

Yup, it all depends on the circumstances for which method is best suited for the job at hand. I agree completely. Nitric oxide gases have a definite odor and a "biting" sensation when inhaled because it reacts with the water in your lungs. Also, The gas has a dark-red/deep-maroon and dare I say pretty color. It is the not so noticeable toxic gases that I am more fearful of. Nitrogen oxides are definitely very toxic like many gaseous elements and compounds. I am sharing information on how to make nitric acid for those who do not have easy access to it or who have never considered using it for whatever reason. I am seriously considering writing a tutorial that details how to make nitric acid easily and safely and posting it in the tutorials section if it hasn't been posted already. All in all, I will eventually try the AP method when I have completed my current projects and I can get around to experimenting with it.

 

[butcher]

Not all NOx gases are visible, and some are hard to detect, with your nose.

 

[JesseSShaw]

I have to assume you are referring to nitric oxide.
here:
http://en.wikipedia.org/wiki/Nitric_oxide

On a side note, I just made another batch of nitric acid. Using 70ml of sulfuric acid and 100g of sodium nitrate, my yield was 37ml of 86+% HNO3 (concentrated nitric acid). Sometimes I double up on the reactants in a larger reaction flask (1000ml) for double yield. I usually have enough for whatever process I need it for. After I have used this batch then I will experiment with this AP method.

 

[Axl_Bundy]

First time poster here, lol.

Can I store old AP solution in an air tight container like a old pickle jar? I will reuse it but want to store it safely for now.

Take care
Ian