help needed not sure what went wrong

so i have 2 batches of pins with high gold content i processed with nitric acid however while one batch striped alot of the gold foils it did not digest the base material and the second set of pins became coted in what looks like rust after a few days i decated the solution and tryd to process differently. my first batch i placed in some hydrachloric acid and had a vigerous reaction but it turned the pins black and dosn't seem to be digesting the base metal.with my second batch of pins i thought maybe an acid peroxide bath might suffice and digest the material but instead it turned the build up on the outside black as well. so im reaching out for help as well my last issue is my gold foils.which i beleive have a build up of metastannic acid but its in the bottom of my ar solution.

Couple questions.
You stated high gold content, but from what info?
Did you see if those were magnetic, because you said a vigorous reaction in hcl.

i used to be a warehouse manager for a ewaste collection company these pins were labeled 18k gold plated in sealed bags i believe they came from one of our telecommunication clients. and i did test to see if they were magnetic and neither batch was. its very possible they are of a lower grade and may have been mislabeled.
the second batch of pins also produced metastannic acid which was decanted with any gold foil for me to deal with later in a collection container. and my main issue is alot of the gold foils is traped inside of the cylinders so i cant just wash and separate them from the pins.

jamiebridges7 said:

i used to be a warehouse manager for a ewaste collection company these pins were labeled 18k gold plated in sealed bags i believe they came from one of our telecommunication clients. and i did test to see if they were magnetic and neither batch was. its very possible they are of a lower grade and may have been mislabeled.
the second batch of pins also produced metastannic acid which was decanted with any gold foil for me to deal with later in a collection container. and my main issue is alot of the gold foils is traped inside of the cylinders so i cant just wash and separate them from the pins.

Click to expand...

There is no 18K gold plating used on any electronics. Also, the electronics industry NEVER uses the term "karat" for gold plating purity -- they always use percent. All gold plating on electronics is at least 99% pure, with only one exception I have seen in 50 years. A company I worked for sold about a 60/40, gold/palladium alloy plating bath for use on reed switches. The plating was white.

So I have 2 batches of pins with high gold content I processed with nitric acid however while one batch stripped a lot of the gold foils it did not digest the base material and the second set of pins became coated in what looks like rust after a few days I decanted the solution and tried to process differently.

Pins will have remaining nitrate salts, now adding the pins to the HCl acid some of the gold will be attacked, as the nitrates form a small amount of nitric acid in the acidic solution, the base metals of the pins cement the gold from solution when the oxidizer is used up and gold in solution is replaced by base metals...


My first batch I placed in some hydrochloric acid and had a vigorous reaction but it turned the pins black and doesn't seem to be digesting the base metal.

With my second batch of pins, I thought maybe an acid peroxide bath might suffice and digest the material but instead, it turned the build up on the outside black as well. so I'm reaching out for help.

Again sounds like you are using too much oxidizer, then cementing the gold back out of solution...




As well my last issue is the gold foils I believe have a build up of metastannic acid but it is in the bottom of my ar solution.

What are you calling "ar" solution?
I do not recall reading above where you tried to make AquaRegia, so what is this"ar" solution?
Tin is another problem we can discuss later.

What are you doing with the solutions you have?

Some pins use other metals like stainless steel sleeves and can be alloys of copper like beryllium, Kovar...

I cannot comment on the processes you have tried like the nitric acid as I do not know any details of what you did.

But it sounds like you do not understand them or the use of acids and metals, or understand how to prepare your materials for processing...

Before discussing recovery, I would rather ask how do you plan on dealing with the toxic solutions you have created up to this point... Then maybe discussing learning how to prep the pins, choosing a recovery method and learning how it works, and gaining an understanding of it...

I agree with Butcher. It sounds like you are cementing your gold back on to the base metals. Dissolving whole pins can be a real pain. You may have made your problem worse by switching the processes you are working with. Hopefully you have kept all of the solutions. You need to be much more detailed about what you've done. If you started both batches in nitric and the concentration was too high it can passivate the pins and they will be resistant to the acid. Once you switched them to HCL there would be left over nitric attached to them that would start to dissolve the foils you wanted to remove. you should test that solution with stannous chloride. The batch that went into AP could have the same problem and you did not mention using an air bubbler in it. Both AP and Nitric digestions of whole pins will take a really long time. I've had AP batches take almost a month to work.

so all of my waste solutions i decant into containers and lable exactly what was put into each container. and when i mentioned my ar solution i was refering to auqua regia which i had digested some foils into ill have to take a picture for you when i get the chance. i thought the foils were clean since i rinsed them with regular tap water a few times. as for my pins i digested in a dilute nitric acid i first added enough distilled water to cover the pins and then added about 200ml of 67% nitric acid to each bath. after few days of letting it soak i decanted the solutions into a storage container for later disposal at a proper hazardous waste station. i then repeated the process as all of the gold foils weren't striped from the first batch of pins and let sit another few days. the second batch i wasn't sure why they had become coted so i rinsed them thoroughly and put them into a oil catch pan i got from the dollar store to inspect them i scraped them with a blade and found they were still gold underneath so i placed one pin in some hcl to test the reaction it cleaned off the outer coating and revealed the large amount of gold as seen. i had previously ran a batch of cylinder which i disolved completely in ar solution but felt like i lost a fair amout of pm, and put the rest of my solution into my drop bucket with spent ar which i denoxed using all my ar solutions with sulphamic acid then filtered and then precipitated the gold out of the solution using smb so any remaining pms i could collect later when i siphoned the solution out of the bucket. so i was trying to use the ap method to essentially disolve the rest of the base metals without having to burn a hole in my pocket for the nitric and hcl. yes i am still learning more about base metals and properly sorting the material i have and deciding the best methods for processing each batch of material. i do believe you are right though in saying im probably using to much oxidizer. as well i do store all of my solutions just in case.

so all of my waste solutions i decant into containers and lable exactly what was put into each container.
i decanted the solutions into a storage container for later disposal at a proper hazardous waste station.


First, this is where I would begin, concentrating on this will help you with the recovery of your gold, and a beginning basic lesson in chemistry, at the Sametime, save you money and grief, up to this point you may have generated a few gallons of toxic waste, your plan at present is not wise, saving large volumes of toxic waste wondering or hoping to get lost values from, which could cost you more than they are worth...

Most of your gold has probably cemented from solution, if not the copper from the pins will cement it out.

Before proceeding, I recommend you do a few experiments to get acquainted, page 11, Hoke's book.
while cementing gold from solution.
Study the reactivity series of metals.
Begin study on dealing with waste found in the safety section.

Your gold is safe now, you may be able to use some of your solutions later, before treating them for waste, depending on what they consist of, or what process you may decide on later, but first let's learn a bit about displacement reactions, how these metals react in solution, problem metals, and many of the chemistry involved by doing some experimenting, we can also learn to test for gold in solution, and the basic principles and a general understanding that will assist you in almost any process, or direction you choose to recover or refine these valuable metals...

thanks butcher i appreciate the response and will definitely look into your recommendations to better help me understand the metals i realize the gold and the copper is cementing back onto my pins and i havnt created to much waste. as for my bucket its just any ar solution i have processd or used when purifying the au and im a hands on learner so i learn as i go and reach out for direction more or less. which is why i added pictures as well for better more accurate descriptions. after read these suggestions and have a more clear understanding in whats going on ill be sure to get back to you for this topic thanks again.

Sounds good, after learning some, you will have a whole bunch more questions, it always starts with one, and before you know it we will have ten more...

For every one question answered, we gain a hundred more answers, as we begin to understand, being able to answer most all of our own questions, as problems arise with our growing newfound understanding...

Easy Peasy. Search the forum

Butcher,

You always amaze me with your patience! Talk about idols, your responses lead The masses.

Rachel

Thankyou

OK so after doing an extensive amount or reading I believe I know what is happening with my experiments. I am not saying I've solved my puzzle, but I believe I am on the right track thanks to the butcher. (Is he really a butcher?)

So for my first batch of pins I believe any carbon or gold is cementing itself back onto my pins, they were not magnetic but I believe the base metal was made of stainless steel.

As for the second batch I believe the pins are made up of a silver and copper composite. And that while I was under the impression that the nitric had run its course I don't think I actually dissolved all my base metals. I think that in my second batch as the acid was making its way through the pins base metal and dissolving the silver it was displacing the copper and cementing it over the gold back to the pin.

As for my first batch when I switched to the AP method I think any carbon deposits began to cement back onto the pins.

Also, I would appreciate any other references to links or directions or threads on the forum to read up on to better my understandings. I am curious about another thing, I believe I did not use the full life of my nitric acid and would like to reuse what I have in a collection bottle to make sure I used its full life span but I’m unsure as to how the chemicals would react with one another at this point.

Is there something I can refer to as of the reaction of just different chemicals and their properties? Like a mixture of nitric acid and hydrogen peroxide and its possible effects or mixing HCl and hydrogen peroxide since its used as a substitute for nitric in poor mans AR?

I made the grammar corrections and paragraphs this one time to show you how much easier it is to understand.

If you want help here, it would be a good start to use paragraphs.
There are members that will totally ignore big long never ending posts with no breaks.
Sentences starting with capital letters would help also.

Making your post using your best writing skills, and using the helpful tools like spell check, will make your post much easier to read, which will assist those reading, the easier to read and understand the better for all of us.

You are getting a general idea of the problems you have had and what went wrong up to this point.

Silver, why do you suspect silver here where from solder?

Carbon can reduce gold, but here it is just a possible contaminant from dirty glassware, oil, organics or coatings on pins, or organic materials like bugs or fallen leaves in your reactions, although a source for problems, here carbon reducing gold is not the problem.

Some of your used solutions can be reused in recovery processes or be used to make other reagents or chemicals for use recovery or refining, it depends on what they consist of.

We can discuss possibly reusing some of your waste acid solutions later.
But, at this point lets discuss:

Waste treatment.

The reactivity series of metals and how the reactions displace other metal ions from solution.
Cementing gold from solution.

Testing for gold and identifying other metals in solution.

Working safely with the deadly gases produced, protecting ourselves and others from the toxic chemicals generated, Basically using safe lab practices.

Gaining an understanding of the reactions we expect, and understanding the problems that can and will follow, also gaining an understanding to be able to figure out our problems and correct them when they poke out their ugly heads.

Choosing methods to prepare our scrap for recovery.

Choosing a recovery process, and understanding its chemistry.

Dealing with problems of the recovery process chosen.

After getting a handle on the recovery of the gold, maybe then we can go on to discuss a little about refining the recovered gold.

You are on the right track, just stick with it, do not let the gold fever pull you off course, jumping in experimenting without gaining an understanding of the basic principles needed to be successful.

Gain the understanding, then use your understanding to experiment, and improve that basic understanding...

Grammer, and spell check, can only improve our communication, making it easier for us to help each other as we share our experiences, and new found understanding...

My first reaction to your thinking is: If you are worried about spending too much on Nitric, then using it to process pins is not a good idea to start with. The electroplating on them is so thin it is a waste to attempt to dissolve all the metal that carries it, as it requires way too much acid. Save your Nitric for refining rather than recovery.

Though I have been disappointed with my scant results (which seems to be a frequent plaint anyway), reverse electroplating is the best bet for recovering gold from pins and any other plated metal parts, unless you are dealing with extremely small and thin pieces, whose base metals would quickly be consumed in an acid leach.


The AP method works so well on circuit board plating (gold on plastics) because the base material is very thin and dissolves relatively quickly. I wouldn't use it for pins, though I notice many people do--and leave them in a bubbling container for a long, long time.

It still is unclear to me exactly when the AP solution is no longer effective, and how to cement out its base metals in order to keep using it indefinitely.


:mrgreen:

Hope it helps.