cyanide leach! cant get 99% Gold recovery

[Geo]

Naive question...

I understand that, for most of the recoveries we do, we tend to use HCl/Cl because it counts as fairly safe (where "safe" means "causes instant burns on contact" as opposed to "one good whiff will destroy your lungs :shock: ); and AR works a good bit easier, though a lot more dangerous and (for most of us) both more expensive and harder to get the reagents.

But for what purposes would we ever intentionally choose cyanide over something safer? This one seems almost like a no-brainer.

/ Not even remotely interesting in trying it, only wondering out of intellectual curiosity.

cyanide leeching will remove PM's from visible areas on electronics without removing gold plated items from the board. gold plating is removed without degrading the base metal substrate. cyanide leaching is used in mining today to remove PM's in mining operations all over the world as it is inexpensive and has a very good reclamation percentage compared to other leaches where base metals can effect the outcome.

 

[loghman1351]

Thank
Please give information on gold electrode in a solution of cyanide

 

[chlaurite]

Thank
Please give information on gold electrode in a solution of cyanide

Look, I don't mean to make fun of your English skills. Honestly, you know English better than I know any other language!

But Cyanide will KILL (matar, tuer, vras, doodmaak, öldürmək, убивать, dræbe, 杀, להרוג ,قتل) you dead, dead, dead, if you don't know exactly how to use it correctly and safely.

Please don't try to scrape together a crude understanding of using cyanide from an English forum unless you have a fluent grasp of English.

 

[Gratilla]

Guys, I think there is just a little bit too much uninformed emotionalism (err, hysteria) surrounding cyanide.

Cyanide, just like many of the other chemicals that we deal with, has its own pros, cons, etc. And it's up to us to become properly informed as to appropriate safety issues.

Here's what Doc Williams has to say about cyanide:

http://webpages.charter.net/kwilliams00/bcftp/docs/cyanide.htm

I for one would much prefer to deal with a cyanide spill than say, hydrofluoric acid or even concentrated AR. Although cyanide reacts with hemoglobin, it is metabolized (ie broken down) by the body and you can recover from minor exposure (although I'm NOT recommending this), in contract to say carbon monoxide, etc.

Be informed, be safe.

 

[solar_plasma]

@Gratilla

Looking at the LC50 of cyanide gas and its fast effect, it is nothing I want to have around me. But you are right, some other materials should scare people much more then they actually do. A burning bed produces HCN. CO kills without you will smell or taste or even feel it and is cumulative under incorporation, too. H2S's toxicity is similar to HCN, but it smells so bad, that intoxications seldomly occur.

But when such materials could be present, you will use some kind of warning method. You have a smoke alarm in your bedroom. A CO-alarm beside your chimney, a gas alarm beside your gas installation. Earlier candles and birds were use in mines. If someone uses cyanide professionally he will have some kind of instrument to measure HCN, a multi-warn, a PID or an IMS or whatever. Those you will not get in your local DIY warehouse and most people, who could get attracted by cyanide, because it is "cheap" will probably not use some thousands or ten thousands of dollars to búy professionall measuring equipment for a hobby.

Yes, AR or ACl are truely dangerous, too, but you see, smell and feel the danger, you have more time to react and it can be handled. I am sure, KCN can be handled, too, but only one little mistake would have much more serious consequences.

I like to READ about the process, because the chemistry is interesting and I'd like to understand it, though I don't even dream of using it. Something I never found an answer for: Why isn't gold cementing back, when leached with cyanide? Everyone who is using cyanide surely knows its chemistry and can answer this!

 

[butcher]

Gratilla,
I agree with you to an extent, many things nowadays are vilified, and many times misunderstood, sometimes the dangers almost seem exaggerated, But then again many times these dangers are very real, and depending on circumstance the dangers may even be underestimated, if a person has a good understanding, Knowledge, skills, and safe working practices he can work with very dangerous materials or do very dangerous things relatively safely, But then again there are always those unexpected incidents, mistakes, human error, or just accidents, and even the well trained professional is killed...

With the people who read just enough to get themselves hurt, thinking they can do this thing that seems so simple to them (not knowing what it really takes or involves, or its dangers)... this forums unwritten policy's of not promoting the use of cyanide. And warning of the dangers, I feel is a good policy, ( I also notice here the most warnings are given by those who do have a good understanding and have used cyanide), just think how many people would mix up a batch with little or no understanding, and would poison themselves or others, thinking they could do something they seen in a you tube video, or something they read in one or two posts on a internet forum, just wanting to get some quick gold without spending the needed time to get the education before trying something stupid.


Be informed, and be safe. Problem is many people will not be informed or be safe.
No doubt about it working with cyanide can be deadly, even for a professional who is well trained.

 

[Gratilla]

Why isn't gold cementing back, when leached with cyanide?

But it is! Although I'm (peripherally) involved with a cyanidation project, we use carbon and not cementation.

Some large operations still use zinc cementation. The main reason that small operators don't have much luck with cementation and discard it is because IMO they don't appreciate/understand the basics and don't use it properly. ie high surface area powder or mesh, (vacuum pump) extract oxygen from pregnant leach first, etc, etc.

The future I believe will be solvent extraction using PH-modified organic solvents.

Butcher, re safety procedures for cyanide: Some months ago I was surprised (maybe even shocked) to hear that the main safety advice for the local artisanals using cyanide was, "If feeling faint or woozy, retreat from cyanidation tank and lie down until recovered." Talk about being cavalier.

 

[freechemist]

Gold Silver Pro writes:

My guess is that the zinc is the problem......

It's not the zinc alone, it's the zinc cyanide formed as well. Zinc cyanide is practically insoluble in water, and forms a protecting cover on the zinc-metal used to cement gold. Thus, the reaction Zn(metal) + 2 [Au(CN)₂]^- => 2 Au(metal) + Zn(CN)₂ + 2 CN^- becomes very slow, or even seems to stop. In my practice a good measure against this passivation of metallic zinc was, to dissolve enough ammonium chloride in the leach-solution to be treated with zinc-powder, before it's addition (10 - 50 g NH₄Cl per liter).
Zinc cyanide dissolves in aqueous ammonia, forming soluble zinc-ammine complexes: Zn(CN)₂ + 4 NH₃ ==> [Zn(NH₃)₄]²⁺ + 2 CN^-. The ammonium-ion, NH₄⁺ is a weak acid, and reacts with free cyanide in solution to hydrocyanic acid, HCN, and aqueous ammonia: NH₄⁺ + CN^- <==> NH₃ + HCN The acid strengths of NH₄⁺ and HCN are about equal, and so neither all added ammonium-cations are deprotonated, nor all free cyanide is protonated to hydrocyanic acid.

 

[Gratilla]

I somehow suspect that cyanide is about to make a comeback:

http://uk.news.yahoo.com/texas-running-lethal-execution-drug-113720871.html#Jb9KegJ

 

[butcher]

Plenty of rope in Texas, just Hang them.

 

[kjavanb123]

Samuel,

I dropped in a steel wool as you did in this threat, into a cyanide solution, here is what it looks like after 24 hrs, please advise how long more does it need to stay?



Thanks
Kevin

 

[dannlee]

Kitchen pot and pan scrubbers usually are stainless steel; the piece shown surely resembles the bright nickel of a pan scrubber...

Steel wool is much cheaper and easily rusted - a common example is pictured:

 

[Lou]

Steel wool is very effective when used electrolytically.

The gold is substantially out of solution (low tens of ppms, then onto resin) when current density drops and much more gas is produced.

 

[kjavanb123]

Dannlee,

Thanks for your info that certainly helped me to use the right materials, plus that explained why I didnt get any plating on this material I used.

Lou,
Could you please elaborate on electrolyical parameters? I read in a post by GSP, he used 6x6 inches stainless steel plates, submerged into 5 gallon bucket filled with cyanide solution connected to 3-4V DC current, is that what you meant? Instead of using cathode use steel wool shown by dannlee?

Thanks and regards
Kevin

 

[Lou]

Yes, use steel wool. Everything else the same. Good stirring is important, heat helps, amongst other key points.

I suppose I could tell you how to do this very well, but I really don't like to see people use CN here on the forum and would rather people not get involved with it. Safety and responsibility are paramount, and this is one of those topics (Pt handling being the other) where if you have to ask, you ought to reconsider or hire someone who knows.

Sorry, but my memory is long in your case kj.

 

[kjavanb123]

Lou,

Thanks for confirming the steel wool concept. As far as hiring someone to tell me how to electroplating gold on ss cathodes, I have no problems but no one has ever pmed me with an agreement even I asked few times . But I thought this was a forum where people share their knowledge.

I cant find the steel wool pictured here so either havr to ball mill my existing troubled zinc powder or find scrap steel wools made in craftiny shops.

Regards
Kevin

 

[Lou]

Any magnetic steel wool that burns with a battery will work.

Yes, the forum is about helping people and sharing information. That doesn't mean forum members are entitled to say everything they know or give information they suspect may not be used properly/responsibly. Free to help/share as much as they please.

You see, some people can follow a written procedure to the "t" and it goes fine. Some people can follow a written procedure to the "t" and it goes wrong. Some people just can't follow any advice, so why give it? FWIW, that's just me sounding off in general.

In any event, steel wool should be everywhere in the world. Find it, use it, make some money. Save every drop of solution until it's tested, then make sure it gets managed responsibly.

 

[butcher]

I have to comment on how helpful Lou has been to this forum, sharing his hard earned knowledge, in many aspects of chemistry and science, and especially in the recovery and refining of the platinum group metals, we are very lucky to have had Lou, who has worked very hard to learn, and have him so generously share his valuable knowledge, with us, for that all most any of us can say is
Thank You Lou.


I have to agree with Lou as far as help goes on this forum, we are not here to help someone get hurt, or get into situations over their head.
And not everything will be shared, sometimes the explanation will be too complicated, dangerous, or sometimes it may be a mans bread and butter, which if given away may lower the bread on this mans table, but in general this forum has given us all a wealth of information, with that and with our own resources and study has been a very valuable gift to us all.

We have to consider also, much of what has been given by members of this forum has been held secret from the general public most of mans history, but with the forum has been shared freely, also giving us a resource for study, that for many of us, would not have had the opportunity to learn it otherwise, what is shared should be considered a very valuable gift, not all secrets will be shared, I guess that is just the nature of secrets.

 

[Justincase]

Just thought as no body has mentioned first aid I would point out.
Any one with cyanide on the premises on top of the having excess quantity's of alcali.
It would be good to have some ampules of Amyl Nitrite on the wall next to any station one might accidentally come into contact with said toxin.
Immediate inhalation of the stimulant is the only real antidote available as it is the only thing that act's quickly enough.
Then followed by an infusion of 300 mg or 10 mg/kg IV sodium nitrate,to be injected over 2-5 minutes, and a 12.5 g sodium thiosulfate IV to be administered over 10 minutes you may repeat both if necessary will give you the best chance of survival.
I know all the legal eagles will say first aid should not cover direct medication but I would much rather take my chance's with a little self medication than wait the half hour or longer that help would take.
This is one instance where seconds count.

 

[goldsilverpro]

The amyl nitrite ampules are called "poppers" in the illegal drug trade.
https://en.wikipedia.org/wiki/Poppers
https://en.wikipedia.org/wiki/Amyl_nitrite

In most of the refineries I worked in, we kept a box of these handy, but I don't remember anyone ever having to use them. It takes a prescription to get them (at least, legally). They are not cheap. I think they are used in case of HCN gas inhalation, which is emitted when cyanide is mixed with any acid. I think the thiosulfate plus sodium nitrite is used for cyanide ingestion. It seems there are better antidotes available today but I think they require administration by IV.
https://www.google.com/search?q=cyanide+antidote&ie=utf-8&oe=utf-8

I remember reading that, when Paul Lynde died, a bottle of butyl nitrite, which produces the same effects as amyl nitrite, was found on his nightstand. This could have been the cause of his fatal heart attack.
https://en.wikipedia.org/wiki/Paul_Lynde

One on the most famous cyanide poisoning events was when a worker died in a Chicago company that was processing scrap x-ray film with cyanide/peroxide. There was even a 60 Minutes segment on it. Most everyone back then used cyanide for film but this changed abruptly after this death. Technically, cyanide is still about the best thing to use for film, since the silver is simply plated out and the solution reused.
http://www.chicagoreader.com/chicago/murder-in-the-air/Content?oid=875834
https://www.google.com/search?q=%22film+recovery+systems%22+golab&ie=utf-8&oe=utf-8

I knew a guy in a film operation that fell into a vat of cyanide solution (as he told me, he was completely submerged) and somehow lived to talk about it. When I knew him, he was still working for the same company, which had long since converted to caustic soda.