Aqua Regia method with 12-13% Ag _inquart_

[kurtak]

One more side note (a bit off topic from this thread) atomized copper powder is the very best way of cementing PGMs from solution - it works much better (for PGMs) then a copper bus bar with a bubbler

And - when done right - you can even cement gold or silver from a solution & have that gold or silver come down with 999 plus purity

Kurt

 

[nickvc]

I believe that you don’t need to use AR when you atomize the gold, I think 4metals suggested using HCl and peroxide as it speeds up the recovery of any PGMs but I’m sure he will correct me if I’m wrong.

 

[4metals]

What is the cons of inquarting?

Inquarting requires more nitric acid, for some that is a problem. If nitric is not a problem the cons are the requirement of the first nitric leach followed by filtration and a second aqua regia treatment. With aqua regia it's a single acid step but there is gold hang up with the Silver and the chlorides are not as clean.

I also thought of this overnight. You can inquart with copper to start, you will use more nitric acid because it takes over 3 times as much nitric to dissolve copper than it takes to dissolve Silver. But once you recover enough Silver from your scrap, you can switch to inquarting with Silver and cut your acid consumption.

 

[4metals]

using HCl and peroxide as it speeds up the recovery of any PGMs but I’m sure he will correct me if I’m wrong.

Actually it's Hydrochloric Acid and either chlorine gas or sodium chlorate. But no nitric.

 

[4metals]

Yes atomizing the gold/silver is another why of going direct to AR (instead of inquarting) as the "ultra fine" particles of gold/silver are so small the silver chloride wont "encrust" the gold in the AR

Yes atomizing is all about the benefit of the increased surface area. Finely atomized karat is small enough that the effect of the encrusting Silver Chloride is less. On solid karat the penetration of the aqua regia is at lease a few mm before the crust starts to form. On atomized karat a few mm is well out the other side of the particle. But you still need to tumble the atomized karat or mix it well because it is so fine it can settle down in the vessel and behave like solid metal. It needs to mix for the full benefit.

The real benefit of atomizing is the ability to dissolve the alloy and the PGM’s in the alloy is the ability to do it without nitric, which simplifies PGM recovery as well.

But in this case I think atomizing is overkill.

 

[andu]

Yeah I understand both inquarting and AR method but I got lost at 8:00, did he take to gold after he inquarted and used it in AR as secondary refine?

Yes he did, and by repeating the whole AR-sulfuric drops it get's cleaner, I suspect the stuff left in the filter and that did pass thru the filter is perhaps lead sulfate. He tends to repeat the process quite a few times. I believe that you don’t need to use AR when you atomize the gold, I think 4metals suggested using HCl and peroxide as it speeds up the recovery of any PGMs but I’m sure he will correct me if I’m wrong.

using HCl and peroxide as it speeds up the recovery of any PGMs but I’m sure he will correct me if I’m wrong.

PGMs tend to stick very well to silver. Peroxide can and will dissolve gold.

 

[snoman701]

Just remelt with a touch of copper so you can get that silver percentage down a bit. Then you can go direct to AR. Even just shotting it out with a tiny amount of copper added will get you below the 10% threshold and allow you to directly digest. When you remelt, instead of pouring an ingot, pour shot into rapidly moving water. GSP posted of shotting into a container mixed via wooden propeller that produced grains the size of sand.

 

[4metals]

Often to get high purity one needs to re-refine with aqua regia. So 2 refines with aqua regia. If you inquart with copper or Silver, and do a final heated leach you can get your gold clean enough to only need 1 aqua regia refine. And you have all of your silver clean as Silver Chloride to reduce to metal by simply dropping it out of the nitric parting solution. And you can recycle the second parting acid to do the first leach on the next batch because the second parting really cleans up what the first parting left behind. It has a lot of free nitric left.
I found, for a small producer, Silver inquarting routinely produced fine gold and fine Silver. Not a lot of time wasted chasing solutions around with a few grams here or a few grams there.

 

[zacchy]

For someone who is learning, it is better to do inquartation with silver and attack with nitric acid, inquartation consists of bringing the gold to 250 grade, adding silver or copper to the alloy. and shot blasting over water. These grains are then attacked with nitric acid in a closed reactor or in a beaker.

You can send me the weight of the gold bar and the grade and I will tell you how much silver you need.

 

[giahylxag]

Often to get high purity one needs to re-refine with aqua regia. So 2 refines with aqua regia. If you inquart with copper or Silver, and do a final heated leach you can get your gold clean enough to only need 1 aqua regia refine. And you have all of your silver clean as Silver Chloride to reduce to metal by simply dropping it out of the nitric parting solution. And you can recycle the second parting acid to do the first leach on the next batch because the second parting really cleans up what the first parting left behind. It has a lot of free nitric left.

I am looking for my first test at the end of the month, I will try to update it frequently. My first goal is to make it as close to 9999 as possible and recover (or at least take into acoount) all the gold (so no unrecoverable gold loss).

I found, for a small producer, Silver inquarting routinely produced fine gold and fine Silver. Not a lot of time wasted chasing solutions around with a few grams here or a few grams there.

Well I am starting small. But my business turnover is around ~3-6kg of 15K scrap a week, I usually melt it, assay and sell them to another guy, but his cut is big. I am trying to make a closed process at the end of next year.

 

[giahylxag]

Inquarting requires more nitric acid, for some that is a problem. If nitric is not a problem the cons are the requirement of the first nitric leach followed by filtration and a second aqua regia treatment. With aqua regia it's a single acid step but there is gold hang up with the Silver and the chlorides are not as clean.

I also thought of this overnight. You can inquart with copper to start, you will use more nitric acid because it takes over 3 times as much nitric to dissolve copper than it takes to dissolve Silver. But once you recover enough Silver from your scrap, you can switch to inquarting with Silver and cut your acid consumption.

I will make my first test with ~20gr (is this enough for a test?) 15K gold with 13%Ag next week or the end of this month. I will try your suggested approach and update

 

[giahylxag]

Just remelt with a touch of copper so you can get that silver percentage down a bit. Then you can go direct to AR. Even just shotting it out with a tiny amount of copper added will get you below the 10% threshold and allow you to directly digest. When you remelt, instead of pouring an ingot, pour shot into rapidly moving water. GSP posted of shotting into a container mixed via wooden propeller that produced grains the size of sand.

 

[giahylxag]

Yes atomizing the gold/silver is another why of going direct to AR (instead of inquarting) as the "ultra fine" particles of gold/silver are so small the silver chloride wont "encrust" the gold in the AR


20 mesh is to big to go direct to AR (without tumbling) (for gold/silver alloy 80/20) for direct AR you need to get the particle size down to 200 - 300 mesh (150 mesh is boarder line)

Here is a GOOD thread on atomization ---------

https://goldrefiningforum.com/threads/is-it-possible-925-sterling-silver-powder.30689/
Kurt

I believe that you don’t need to use AR when you atomize the gold, I think 4metals suggested using HCl and peroxide as it speeds up the recovery of any PGMs but I’m sure he will correct me if I’m wrong.

Just remelt with a touch of copper so you can get that silver percentage down a bit. Then you can go direct to AR. Even just shotting it out with a tiny amount of copper added will get you below the 10% threshold and allow you to directly digest. When you remelt, instead of pouring an ingot, pour shot into rapidly moving water. GSP posted of shotting into a container mixed via wooden propeller that produced grains the size of sand.

Atomizing is the newest thing I know. I don't know much about this process and will try to understand it in a near future. I heard that someone already make a machine for that (cost ~15k$ made in china)

 

[4metals]

For a 200 oz process lot I would be setting up a spherical glass reactor with a condenser to reflux the acid fume. The 72 liter flask shown is mounted in a tipper so it can be tipped over and poured into a filter to drain it. The capacity of a 72 liter reactor is 300 ounces. They make 50 liter reactors which can handle 200 ounces and both the 72 and the 50 need to be mounted in the tipper they also make a 20 liter flask which can handle 100 ounces. The 20 liter flask is small enough to be lifted and poured by hand. You could do the inquarting and aqua regia refining in these reactors but I would do the nitric parting in the plastic cement mixer I mentioned earlier.
I would also invest in an Italimpianti filter trolley which allows you to pour anything you need to filter into the funnel. The rig pulls its own vacuum with a double diaphragm pump and discharges wherever you choose for the next process. All you need is an air compressor to power it.

The top photo is the filter trolley and the bottom photo is a 72 liter flask in the tipper with the condenser mounted in a hood. Since the heat mantles have 2 heat zones, you can buy the 72 liter and process smaller lots by only using the bottom heat zone. I have never purchased a 50 liter vessel, just 72's and 20's.



To get a feel for this process, I would process at least enough for a 4 liter flask. That means using a larger vessel for parting the inquarted alloy and finishing up with about 15 ounces for the 4 liter aqua regia reaction. I have found that small lots have larger losses. Since you are looking to track every milligram, your test refine should be more than a few grams or you will be thinking it is less efficient than a larger production lot would be.

I usually melt it, assay and sell them to another guy, but his cut is big

what do you consider a big cut?

 

[giahylxag]

For a 200 oz process lot I would be setting up a spherical glass reactor with a condenser to reflux the acid fume. The 72 liter flask shown is mounted in a tipper so it can be tipped over and poured into a filter to drain it. The capacity of a 72 liter reactor is 300 ounces. They make 50 liter reactors which can handle 200 ounces and both the 72 and the 50 need to be mounted in the tipper they also make a 20 liter flask which can handle 100 ounces. The 20 liter flask is small enough to be lifted and poured by hand. You could do the inquarting and aqua regia refining in these reactors but I would do the nitric parting in the plastic cement mixer I mentioned earlier.
I would also invest in an Italimpianti filter trolley which allows you to pour anything you need to filter into the funnel. The rig pulls its own vacuum with a double diaphragm pump and discharges wherever you choose for the next process. All you need is an air compressor to power it.

The top photo is the filter trolley and the bottom photo is a 72 liter flask in the tipper with the condenser mounted in a hood. Since the heat mantles have 2 heat zones, you can buy the 72 liter and process smaller lots by only using the bottom heat zone. I have never purchased a 50 liter vessel, just 72's and 20's.
View attachment 60754View attachment 60753


To get a feel for this process, I would process at least enough for a 4 liter flask. That means using a larger vessel for parting the inquarted alloy and finishing up with about 15 ounces for the 4 liter aqua regia reaction. I have found that small lots have larger losses. Since you are looking to track every milligram, your test refine should be more than a few grams or you will be thinking it is less efficient than a larger production lot would be.

Much appreciate your effort writting such detail explanation!
I don't have a source or importer imports Italimpianti products in my country, I may have to improvise some but for sure it seems purely mechanical and not something out of my ability. I will update when I make larger scale experiment

what do you consider a big cut?

Well I got charge 1.5% of the total weight. It mean if I have an 1000g alloy with %Au=61,5% I will get back 600g Au in term of money. It may higher or lower depending the composition of the alloy. I want to refine my own goods, when you have stock like 1kg of 9999 bars you can easily trade on the market. Most bullion dealers just don't want to buy gold scrap.

 

[4metals]

1.5% of the total recoverable gold isn't terrible but for the quantity you ship you should do better yourself. Do you get paid for the Silver?

One thing to consider though is how will you get rid of the refined metal. Here in the US refiners your size turn it around through large refineries for about $1 to $1.50 an ounce on the incoming weight with an accountability of 99.5 %. The accountability is the 0.5% charge which your refiner sets at 1.5%. But the refiner buys the metal and you don't have to find a market. Unless you have jewelers lined up to buy your refined gold you will likely be paid under spot for your refiner to buy it.

I may have to improvise some but for sure it seems purely mechanical and not something out of my ability. I will update when I make larger scale experiment

I have better photo's of the filter with images of the insides which may help when you are ready.

 

[giahylxag]

1.5% of the total recoverable gold isn't terrible but for the quantity you ship you should do better yourself. Do you get paid for the Silver?

No I dont get paid for the silver

One thing to consider though is how will you get rid of the refined metal. Here in the US refiners your size turn it around through large refineries for about $1 to $1.50 an ounce on the incoming weight with an accountability of 99.5 %. The accountability is the 0.5% charge which your refiner sets at 1.5%.

My English is not good I don't get it. How this would be translated in my term? Is it the refineries cut is 0.5%? I don't have professional refineries here like in the US has Metalor or Kitco. It is like some local dude jewelers who know the trick to make it. So their cut may be big.

But the refiner buys the metal and you don't have to find a market. Unless you have jewelers lined up to buy your refined gold you will likely be paid under spot for your refiner to buy it.

I can find a dealer and they will be very happy buying my 9999 products. 1kg minimum quantity. Believe it or not gold buy/sell spread here is 1.6% to 0.5% if you sell 1kg or above (but quality must be >999)

 

[4metals]

No I dont get paid for the silver

If you are not paid on silver a 6 kilo lot (192.9 oz) running an average of 12%Silver will cost you 23 oz of Silver which at the current price of $24 an oz is worth $554. Yeah you will be much better off refining yourself.

My English is not good I don't get it. How this would be translated in my term? Is it the refineries cut is 0.5%?

Yes the refinery charges 0.5% plus the per ounce incoming fee. The word accountability is an accounting magic term so the actual 0.5% they charge doesn't show up on an invoice as a charge. For example, if you sent in 100 ounces of gold to refine, the charges here in the US would show the incoming fee, so $100 or $150 based on your quote. If the gold was an assay of 15 k (like yours) they would charge .625 x 100 = 62.5 oz. Since the accountability is 0.5% the paperwork will only multiply th 62.5 by 99.5% and report 62.1875 ounces. You get back or get paid on 62.1875 and they keep 0.3125 oz. But only the incoming charge has a dollar figure on the paperwork. They also pay on silver with different charges. It is confusing, I know plenty of English speaking Americans who don't really get it.

 

[giahylxag]

Yes the refinery charges 0.5% plus the per ounce incoming fee. The word accountability is an accounting magic term so the actual 0.5% they charge doesn't show up on an invoice as a charge. For example, if you sent in 100 ounces of gold to refine, the charges here in the US would show the incoming fee, so $100 or $150 based on your quote. If the gold was an assay of 15 k (like yours) they would charge .625 x 100 = 62.5 oz. Since the accountability is 0.5% the paperwork will only multiply th 62.5 by 99.5% and report 62.1875 ounces. You get back or get paid on 62.1875 and they keep 0.3125 oz. But only the incoming charge has a dollar figure on the paperwork. They also pay on silver with different charges. It is confusing, I know plenty of English speaking Americans who don't really get it.

I see the difference here. My refinery charges me, let's for simplicity say 0.5%, but that is on the total weight of the bar. So in my math, I only get 62.0000 oz not 62.1875oz. Beside incoming fee 1$/oz is not much a problem
So the actual gold accountability in your term, for me, is really 1-0.5/62.5 = 99.2% not 99.5%,

 

[4metals]

my business turnover is around ~3-6kg of 15K scrap a week,

I'm a number cruncher and from this average quantity of scrap weekly, you are processing an average of 4.5 kg a week for 50 weeks (I give you 2 weeks off for vacation). That comes to 144.675 x 50 = 7,233.75 ounces of karat averaging .625 Gold assay. And .12 assay for Silver will yield 868.05 ounces of Silver

Processing yourself you will save at least 22.6 oz of gold assuming you will save 0.5% over what you are being charged now. (and this 0.5% is a low ball savings, with experience you will get your costs lower) Annual savings at $2000 gold = $45,200
The Silver at 12% amounts to 868.05 x $24 = $20,833

If you are making money with an outside refiner you can expect to make an additional $66,033 by doing it in house at your current quantity of refining. And you have said you will be able to sell your gold over spot for even greater profit. And I am sure you will find a market for Silver to jewelry manufacturers as well.

Hopefully these figures will make you end your year on an optimistic note and looking forward to setting up your own refinery.