Refining Precious Metals as a Business-Startup

[ultimatebullionstacker]

I'm not new to handling metals, I've operated & still am running a foundry for over a decade now but refining is very new territory for me.
Some of our equipment should crossover and we have the space to operate, so our curve to entry should be reduced but very importantly, we have access to feed-in material providers and precious metal buyers are all at hand and well-established within our existing network.
Some of the equipment we have are as follows:
- Induction melting equipment
- Melting furnaces
- Extraction and ventilation set up and in place.
- XRF device
We take in a lot of gold that is alloyed with palladium, with the palladium price so high in recent years, it will be of large benefit if I can separate these to begin with.
My basic question is where to start with the chemicals and various other hardware, trying to be smart with it in terms of being able to scale up quickly if needs be. Any pointers to specific threads would be a great help at this stage.
We have about 300 square feet of space we can utilize at the beginning, with more that can be added if we go further along.
For us, the goal will be to get up and running at a reasonable cost and timescale, I suspect the learning curve will be steep enough, but we're willing to learn on our feet and put in the extra effort to meet the end goal of offering a homegrown solution for refining material, which isn't being offered currently.

 

[nickvc]

Your needs are going to be relative to what you actually want to do but the first thing you are going to need is a decent fume hood with extraction and fume scrubbing for the out put especially if you are in an area with neighbors, chances are that these days you will probably need licenses from government agencies which can be a pain to get.
To get more definitive answers you need to specify your aims and the quantities you intend to refine and to what quality, there is no simple answer I’m afraid.

 

[4metals]

Good start, you can melt it, and do a basic assay on it, (via XRF) now all we have to do is show you how to refine it!

First off you will need a good exhaust hood. There are many threads here on the forum concerning hoods and building them, a DIY section in the library will get you started on that project. I do not pretend to know the environmental regulations on your side of the pond but here in the USA we have what is called a de minimus standard which varies slightly state by state but basically for NOx, the major airborne pollutant refiners deal with, we are allowed to apply for a permit and the de minimus standard will allow us to generate 10 pounds per day of NOx fume without a scrubber. You should check about your local reg's because at the start up quantities you mention in your "new fan" thread, you will likely use less than 10 pounds of nitric in any given day. But as you grow, you will eventually need to scrub your fumes and there are also threads about scrubbers in the library.

For the start up quantities you mention I am assuming your reactions can take place in glass 2 or 4 liter beakers. General rule of thumb, a liter of aqua regia will dissolve about 7.5 troy ounces of metal. And general rule of safety is never fill a vessel over half full to prevent boil overs, which, sooner or later, you will learn about. Using these two factoids you can digest 7.5 ounces in a 2 liter. beaker and 15 ounces in a 4 liter beaker. In the last few years I have been seeing 5 liter beakers as well, so following the same logic you can get 18.75 ounces in a 5 liter beaker.

To refine you will need vessels to dissolve your metal in, as listed above, and filters to filter the solutions with and flasks to filter the solutions in to. And a vacuum source. The industry standard filter is a buchner funnel for vacuum filtrations and a speed funnel for gravity filtrations. I could provide you with links to find these things but my links would be for availability here in the US, possibly some of our European members could help here with more useful links.

I could sit here and type all day but I do not want to be the only source of information for you here, there are many capable refiners who can and will chime in. But as far as actual refining, let me start with this;

I think you should concentrate on perfecting Gold and Silver refining first but since you mention a feedstock containing Gold and Palladium, I think you will need to go down the Palladium road pretty soon. So before I leave this thread to allow others space to comment, I think you should investigate inquartation with Silver to start your refining venture. Inquartation is a valuable tool because it allows you to avoid the dreaded Silver Chloride encrustation that Silver in karat gold can cause. By making your starting alloy 3 parts by weight Silver, you can do a preliminary parting in nitric acid and remove all of the silver and base metals leaving the gold behind undissolved for further refining. Some refiners use inquartation and some do not for karat gold. (if the Silver in the starting alloy is below 8% you can get by without it) But in your case, with the Palladium in the alloy, we can take advantage of the fact that Palladium dissolves in nitric acid. So inquarting will also allow you to separate the Palladium from the alloy early in the game and recover the Gold first, the Silver second, and leaving you with Palladium in solution which you can easily cement out and accumulate for a separate Palladium refine. An in depth explanation of what I just wrote will follow, (either by me or many other refinaholics we have here) I just wanted to get the basic concept out there to get you thinking along those lines.

You have a lot to learn about refining from testing for complete precipitation to treating your waste. But we can cover it all. And if we do it in an organized fashion, topic by topic, it will become a valuable tool for many in years to come. I will take on the responsibility, undoubtedly helped by other moderators, to keep this thread on track so it is easier to follow.

To start, go to the Library and find both a screen readable and printable version of Hokes book, she covers a lot in the book but it will teach you some buzz words to make what we cover on this thread more understandable.

Again, welcome to the forum.

 

[4metals]

Start your reading here;

Printer friendly copy of Hoke's book

Screen readable copy of Hoke's book

 

[orvi]

I'm not new to handling metals, I've operated & still am running a foundry for over a decade now but refining is very new territory for me.
Some of our equipment should crossover and we have the space to operate, so our curve to entry should be reduced but very importantly, we have access to feed-in material providers and precious metal buyers are all at hand and well-established within our existing network.
Some of the equipment we have are as follows:
- Induction melting equipment
- Melting furnaces
- Extraction and ventilation set up and in place.
- XRF device
We take in a lot of gold that is alloyed with palladium, with the palladium price so high in recent years, it will be of large benefit if I can separate these to begin with.
My basic question is where to start with the chemicals and various other hardware, trying to be smart with it in terms of being able to scale up quickly if needs be. Any pointers to specific threads would be a great help at this stage.
We have about 300 square feet of space we can utilize at the beginning, with more that can be added if we go further along.
For us, the goal will be to get up and running at a reasonable cost and timescale, I suspect the learning curve will be steep enough, but we're willing to learn on our feet and put in the extra effort to meet the end goal of offering a homegrown solution for refining material, which isn't being offered currently.

Hi.
Welcome here if you want some information about actual processes and actual refining of precious metals, you are in the right place here. Many experienced members and even professionals with decades of experience in real refining business.

In many terms, you have better start to the "refining" as many other members here. From what you said, you are established in the "(s)melting" business. If that is true, that means you can afford to buy basic equipment to somehow kickstart the learning and optimization process.

Owning induction furnances and XRF gun is a must for quick and reliable work around precious metals, and this will give you big advantage over others who lack these ones. From my personal experience, lacking these two is major drawback for majority of members here, which want to somehow scale up their operation. It gives you confidence to know what you produced (XRF) and induction speeds everything up (if we compare it to ordinary electric/gas furnance, mainly if we are talking about platinum group metals).

But to start doing anything with hydro-chemistry and refining, you will need to have a working reliable fumehood. There are numerous guides on the forum how to build one, but you are in a different situation as majority of hobby-guys here and some vague looking plywood construction simply wouldn´t work for you, as you must probably comply regulations and stuff. Good modular hoods can be made from 1 m3 HDPE plastic vats (IBC container), so if you can have some DIY built, this can be way to go for few bucks. If this is not an option, I would try to contact your partners and look for any industry auctions or marketplaces to buy some regular hood second-hand. Aim for ones that do not have sheet metal construction, as these will disintegrate from fumes in short time.

My questions are:
1. How much you are familiar with basic inorganic chemistry and redox reactions in general ? I am asking because now you will enter the "hydro" chemistry, not "pyro" chemistry. They have some things in common, but from my point of view, hydrometallurgy can be more difficult to understand. Chemistry of gold and silver is fortunately quite simple, but palladium and other platinum group metals chemistry (PGMs) isn´t.

2. Do you have access to buy basic inorganic chemicals in bulk ? Mainly speaking about nitric acid, as in EU, this is controlled substance and you need to have license to purchase it. Other "must have" chems that you will need are hydrochloric acid, sodium hydroxide, sodium metabisulfite, and speaking of palladium - probably dimethylglyoxime (DMG), ammonium chloride and formic acid (these do not need to be in bulk, kilo/liter of these for start is more than enough, for DMG, probably 100g is OK).

3. Describe the grades of typical feedstock (at least in general). Is it metallic, powder/ingots/mixed scrap, how much gold/palladium/silver it has, what are base metal constituents of it (espetially important is presence of "troublesome" metals like tin, bismuth or lead) etc.
4. What is appeoximate scale of the operation, assuming you have already gained the needed experience/know the processes etc. In other words, if everything will go nice and smooth, what is your target scale of processing. Hundreds of grams of feed, few kilos/month, hundreds of kilos/month etc... This will determine and justify the use of various equipment as well as different processes used to minimize work and ammount of waste generated.
5. Do you have the some waste management already established for liquid waste, or good contacts for waste disposal site, where you can dispose waste you will produce ? Thing is, your waste would most probably be acidic heavy metal chloride/nitrate solutions. And many companies charge hefty fees for this kind of waste. It would be good to know beforehand what are the rates applied for different kinds of waste - because it will eventually be produced, and in large quantities as you will scale up. Because waste treatment can be done by yourself, but it adds additional work and chemicals, so it need to be considered beforehand if it is financially OK to just pass it to the waste management company and pay for it.

Most important thing now is to get familiar with chemistry (if you already are, good for you) of the precious metals of your interest (Ag,Au, Pd) and also with redox chemistry in general. You will definitely encounter some problems during your journey, and theoretical knowledge of the processes will help you many many times resolving peculiar situations that can and will happen to you.

 

[4metals]

So far everyone has recommended a good fume hood. And a non metallic hood is best for longevity. Just to make you drool a little I'm going to show you a typical plastic professionally made hood. This one is 8 feet long and 24" deep for a nice sized work area. The plastic drops coming down feed into a fume scrubber. Here in the states there are 2 types of emissions, a scrubbed emission (where the nasty fumes go) and a fugitive emission where only fumes that escape the scrubber go. Like fumes emitted when you pour some acid into a vessel or uncover a reaction for a short time. The reason for 2 types of emission points is if you were to scrub all of the air needed to provide the desired airflow for the overall hood, the scrubber would need to be enormous to give the fume the required retention time. By sucking less air directly from fuming reactions you can get by with a lot less airflow and hence, a smaller scrubber.

you may notice the pipe connecting the 6 drops leading to the scrubber dumps right into the main exhaust pipe. That was because this customer was under the 10 pounds of nitric per day limit so we set it up so the worst fumes are still sucked into the manifold to make the work environment cleaner and because we figured eventually he would grow to need a scrubber and the installation could simply involve redirecting that 4" pipe through a scrubber. He eventually did need a scrubber and another hood. And as the OP mentioned ease of expansion matters.

I think you will find corrosion resistant blowers to be quite expensive. For every square foot of hood opening the recommended airflow is 100 CFM. So for an 8 foot hood, with an opening 8 feet by 3 feet tall, you will need a 2400 CFM blower. (sorry it is too late at night for me to do the metric conversion thing!). But notice the hood has a plexiglass visor that folds up. It is down in the photo but when you are working at moving stuff in the hood or pouring it can fold up and out of the way. But when it is down it halves the open area and allows a smaller blower. The visor still has enough room to easily reach under and add chemicals or pour acid into a filter or whatever and still provide both a smaller opening and eye protection, which is never a bad thing.

This is something I never thought of;

Good modular hoods can be made from 1 m3 HDPE plastic vats (IBC container), so if you can have some DIY built, this can be way to go for few bucks.

An IBC, mounted at a convenient hood height, with the cage cut off the front where the hood opens, and something close to a 36" square opening will make a very nice start up hood. You can fashion a visor to drop down and provide less CFM requirements as described above, and protect those eyes. One little hint, when you cut out the hole for the work area access, keep the cut at least 3" above the bottom. This will provide a spill capturing floor which, believe me, sooner or later you will appreciate.

 

[4metals]

While we are still on hoods, if you do go with an IBC for your first hood (which I think is a great idea, thank you Orvi!) you may find it gets a little dark in the hood and it is good to be able to see the reactions, especially when you are looking for end points. A handy way to install a bright light that will never corrode because the fumes never hit the light is to get a clear glass pie baking dish with a flange, and a chicken brooder light fixture.



Make sure the light fixture sits flat on the bottom of the pie dish and cut a hole in the front and center of the top of the IBC hood. The hole should be big enough for the dish to rest on the flange and not fall into the hole. Then silicone the pie plate in place.

Place the light in the pie plate, turn it on, and experience the light you will appreciate when looking into those reactions and seeing clearly. And the good thing is the light fixture is not exposed to the fumes but you get all of the light inside the hood.

 

[orvi]

While we are still on hoods, if you do go with an IBC for your first hood (which I think is a great idea, thank you Orvi!) you may find it gets a little dark in the hood and it is good to be able to see the reactions, especially when you are looking for end points. A handy way to install a bright light that will never corrode because the fumes never hit the light is to get a clear glass pie baking dish with a flange, and a chicken brooder light fixture.

View attachment 59967View attachment 59968

Make sure the light fixture sits flat on the bottom of the pie dish and cut a hole in the front and center of the top of the IBC hood. The hole should be big enough for the dish to rest on the flange and not fall into the hole. Then silicone the pie plate in place.

Place the light in the pie plate, turn it on, and experience the light you will appreciate when looking into those reactions and seeing clearly. And the good thing is the light fixture is not exposed to the fumes but you get all of the light inside the hood.

I think IBC hood was the most usable/user friendly/actually working without many if´s & issues DIY idea I have ever had We made them, used them for a while, but unfortunately, I didn´t took any photos from their use and manufacture, due to agreement with my friend/partner in refining.

IBC containers are made from quite thick HDPE = perfect corrosion resistance from common and cheap materials. The structure is reinforced by the metal cage and hold well even if the majority of one side of it is removed for the hood opening.

Filling opening on the top serve as very convenient fitting for fume ducting.

Valve on the bottom makes cleaning the spillovers or accidental foam-overs very easy to clean - you take garden hose with spray nozzle, wash interior and then conveniently discharge from the valve to the bucket. No hassle.

HDPE isn´t soaking anything, unlike plastic-wood composite or straight wood.

It´s modular - meaning you can setup a bench and have multiple ones in a row for different things. We had 3 of them in one row, placed onto concrete bench. One for bulk dirty work (AR dissolutions, PGM "messy" work etc.), one for fine work and analytics (gold refining, testing, sample testing etc.) and third for silver processing (to avoid HCl fumes getting absorbed into containers with silver nitrate).

With angle grinder, handsaw, suitable piece of plexiglass, some plastic screws, PE wrapping foil (better for sealing the joint between ducting and IBC than duct tape) and some basic tools, you can convert generic IBC container to workable hood in less than a day.
Here, typical price of clean, used IBC is around 50-100 USD. Always take one with biggest filling opening to fit the widest ducting as you can to maximize airflow.

 

[4metals]

Looks like the OP has gone silent. Too bad, this had the potential to be an informative thread both for the OP and future members setting up shop.

 

[wilsontaylor]

I'm not new to handling metals, I've operated & still am running a foundry for over a decade now but refining is very new territory for me.
Some of our equipment should crossover and we have the space to operate, so our curve to entry should be reduced but very importantly, we have access to feed-in material providers and precious metal buyers are all at hand and well-established within our existing network.
Some of the equipment we have are as follows:
- Induction melting equipment
- Melting furnaces
- Extraction and ventilation set up and in place.
- XRF device
We take in a lot of gold that is alloyed with palladium, with the palladium price so high in recent years, it will be of large benefit if I can separate these to begin with.
My basic question is where to start with the chemicals and various other hardware, trying to be smart with it in terms of being able to scale up quickly if needs be. Any pointers to specific threads would be a great help at this stage.
We have about 300 square feet of space we can utilize at the beginning Check this out, with more that can be added if we go further along.
For us, the goal will be to get up and running at a reasonable cost and timescale, I suspect the learning curve will be steep enough, but we're willing to learn on our feet and put in the extra effort to meet the end goal of offering a homegrown solution for refining material, which isn't being offered currently.

Hello. I've seen a number of different ways to remove gold from boards etc, but I'm going to try vinegar, salt and hydrogen peroxide, as it's all cheap and relatively safe. My question is, does it matter what the material is- plastic connectors with gold pins inside, chips, ribbon cable ends, gold fingers on boards? I've got about 6 different kinds, there's even gold in some kind of part attached to some carburetors, encased in plastic. I'd like to just chuck it all in together, but I've seen so many different methods including grinding everything up and heating it in furnace, boards, chips and all. Any advice?

 

[Golddigger76]

Hello. I've seen a number of different ways to remove gold from boards etc, but I'm going to try vinegar, salt and hydrogen peroxide, as it's all cheap and relatively safe. My question is, does it matter what the material is- plastic connectors with gold pins inside, chips, ribbon cable ends, gold fingers on boards? I've got about 6 different kinds, there's even gold in some kind of part attached to some carburetors, encased in plastic. I'd like to just chuck it all in together, but I've seen so many different methods including grinding everything up and heating it in furnace, boards, chips and all. Any advice?

No acid solution is relatively safe once metals are dissolved into them.
Vinegar is a acid but it is not very good at dissolving metals, just go with hydrochloric acid and a little hydrogen peroxide.
Search the forum for the copper chloride method, this is the cheapest and most effective way to remove base metals from gold plating.

 

[anarxi]

Great, you gave me the idea that I could make a fume hood out of a used canister of nitric acid.
for a small glass.

4 Metals and Orvi, you are incredibly responsive people.
Everything was explained very clearly and concisely.
Perhaps that’s why the topic died out - you told everything right away.

 

[Yggdrasil]

Hello. I've seen a number of different ways to remove gold from boards etc, but I'm going to try vinegar, salt and hydrogen peroxide, as it's all cheap and relatively safe. My question is, does it matter what the material is- plastic connectors with gold pins inside, chips, ribbon cable ends, gold fingers on boards? I've got about 6 different kinds, there's even gold in some kind of part attached to some carburetors, encased in plastic. I'd like to just chuck it all in together, but I've seen so many different methods including grinding everything up and heating it in furnace, boards, chips and all. Any advice?

I could take the welcome act again.
You did not indicate you had plan to refine in your first post.
But here it is:
The things you need to study first.
I recommend you set your stuff aside while you study.

We ask our new members to do 3 things.
1. Read C.M. Hokes book on refining jewelers scrap, it gives an easy introduction to the most important chemistry regarding refining.
It is free here on the forum: https://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=19798
2. Then read the safety section of the forum: https://goldrefiningforum.com/forums/safety.47/
3. And then read about "Dealing with waste" in the forum: https://goldrefiningforum.com/threads/dealing-with-waste.10539/

Suggested reading:
https://goldrefiningforum.com/forums/the-library.101/
https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/
https://goldrefiningforum.com/threa...le-read-this-before-you-post-about-ore.33333/


Forum rules is here.
https://goldrefiningforum.com/threads/gold-refining-forum-rules.31182/

 

[Mzingaye]

I'm not new to handling metals, I've operated & still am running a foundry for over a decade now but refining is very new territory for me.
Some of our equipment should crossover and we have the space to operate, so our curve to entry should be reduced but very importantly, we have access to feed-in material providers and precious metal buyers are all at hand and well-established within our existing network.
Some of the equipment we have are as follows:
- Induction melting equipment
- Melting furnaces
- Extraction and ventilation set up and in place.
- XRF device
We take in a lot of gold that is alloyed with palladium, with the palladium price so high in recent years, it will be of large benefit if I can separate these to begin with.
My basic question is where to start with the chemicals and various other hardware, trying to be smart with it in terms of being able to scale up quickly if needs be. Any pointers to specific threads would be a great help at this stage.
We have about 300 square feet of space we can utilize at the beginning, with more that can be added if we go further along.
For us, the goal will be to get up and running at a reasonable cost and timescale, I suspect the learning curve will be steep enough, but we're willing to learn on our feet and put in the extra effort to meet the end goal of offering a homegrown solution for refining material, which isn't being offered currently.

 

[4metals]

Everything was explained very clearly and concisely.
Perhaps that’s why the topic died out - you told everything right away.

When people post with a reasonable question we don't hold back. We try to help and hopefully engage in a give and take relationship where the original poster gives us feedback and we try to provide useful information.

There are many examples on the forum of members posting and receiving valuable information and engaging in informative discussion. Unfortunately this isn't one of those threads.