Waste treatment system at Gold Refinery

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Nice job on the cementing fixture. That will do the job.

The problem is there isn’t a lot to cement out, the solution looks pretty clear (blue is mostly copper, and that will not drop). Did the solution show positive results with stannous chloride? One or 2 grams of precious metal may come out of solution and it is barely detectable. If you used aluminum you would think you got a lot out but most of it isn’t precious and it’s a mess to separate.

I still think your missing gold is in the silver chlorides. Have you separated the gold from the reduced chlorides yet?
 
4metals said:
Nice job on the cementing fixture. That will do the job.

The problem is there isn’t a lot to cement out, the solution looks pretty clear (blue is mostly copper, and that will not drop). Did the solution show positive results with stannous chloride? One or 2 grams of precious metal may come out of solution and it is barely detectable. If you used aluminum you would think you got a lot out but most of it isn’t precious and it’s a mess to separate.

I still think your missing gold is in the silver chlorides. Have you separated the gold from the reduced chlorides yet?
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We have not yet recovered the silver chlorides and collected them all in gallons. The stannous test for the solution showed nothing.

But, important point, our least lost gold is related to the operation that we added the AL -sludge from the previous process to Tumbler in new operation . Our efficiency was 99.81 %.
 
Gold.refinery said:
The stannous test for the solution showed nothing.
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You mean the waste acid after the precipitation process showed nothing on the stannous I assume. If that is the case you can skip the process entirely and go right to waste treatment. If there is Platinum in the solution
the stannous will indicate it.

I always preferred to have a cementation tank always bubbling. Every lot processed went into it even if it exceeded the 99.75% recovery standard. With jewelry related feed, there can always be a touch of Platinum or Palladium and cementation will catch it. But you should not be running it on a lot by lot basis. It takes a while for values to accumulate to justify processing. Only concentrate on lots with losses in excess of 0.25% to find losses and then only after processing the silver chlorides for that lot.
 
4metals said:
only after processing the silver chlorides for that lot.
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If you are processing 25 kilo lots with a silver content of 7.5% it is relatively quick and easy to quickly reduce the chlorides to metal using either the sugar and caustic or the sulfuric and iron. You will only be looking at 60 or so ounces of chlorides, a manageable volume. Once it is reduced you can re-dissolve the metallic silver in nitric and filter out the gold. This is one of the things I would recommend doing in a hood. Another option is to melt the reduced silver into a bar and take a dip sample and part an accurately weighed sample to determine the gold content. Then when you have enough gold worth going after you can do it on a larger scale. The ability to find the gold content in the chlorides quickly allows you to put the lot to rest and move on. Chasing small quantities of gold is too costly but determining that you haven't lost it is important.
 
4metals said:
You mean the waste acid after the precipitation process showed nothing on the stannous I assume. If that is the case you can skip the process entirely and go right to waste treatment. If there is Platinum in the solution
the stannous will indicate it.

I always preferred to have a cementation tank always bubbling. Every lot processed went into it even if it exceeded the 99.75% recovery standard. With jewelry related feed, there can always be a touch of Platinum or Palladium and cementation will catch it. But you should not be running it on a lot by lot basis. It takes a while for values to accumulate to justify processing. Only concentrate on lots with losses in excess of 0.25% to find losses and then only after processing the silver chlorides for that lot.
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The last efficiency of our operation was 99.64%.

As I said before, nothing was achieved after working with copper plates.
We have about 200 liters of solution.
For the test, we reacted about 8 liters of solution with 50 g of AL. No sludge was obtained and only a very small amount.
We tested the small sludge, showed:
1.6/1000 Au
0.8/1000 Pd
986/1000 Cu
4.3/1000 Fe
5.3/1000 Cd
0.7/1000 Rh

There are 200 liters of solution left and I am undecided.

I'm confused and very tired. I hardly get through the days.

From previous operations, we have several hundred grams of copper powder containing 2/1000 gold.
Can they be recovered?
Is there an economic justification?
 
Gold.refinery said:
From previous operations, we have several hundred grams of copper powder containing 2/1000 gold.
Can they be recovered?
Is there an economic justification?
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Several hundred grams, let's call it 500 grams. 2/1000 as gold. So you are getting burnt out over 1 gram of gold? At today's prices that is worth about $60.

There are many reasons that small amounts of values will get through the system. foremost will be the filtration medium or the equipment you use to filter it. We discussed adding the in line vertical spiral wound filter to the discharge line after you precipitate the precious metals. That tightly wound, often under 1 micron filter should trap any fines. But you will never be able to quantify it but some day that filter will be worth processing.

How did you arrive at the values you showed for the sludge of copper powder? I hope it was by dissolution followed by instrumentation. I would never rely on XRF for that analysis.

I again recommend you start processing some silver chlorides. I would bet the farm they are the hiding place for your missing gold, but you insist on chasing rather insignificant values in sludges.

Process the chlorides, it isn't difficult. We can work you through simple questions here and once you find the gold that you are obviously being whipped for "losing" you will rest better.

Also, keep in mind the sludges you recover from your filter press are typically dried, incinerated, crushed and sifted to make a product to ship to a copper smelter. That is where any lingering PM's will be found. Although if it is high in Cadmium, the incoming penalties will exceed the recovered value.
 
0,1-0,2 % in sludges is relatively OK, much much better than previous 2% :)

As 4metals say, focus on processing the silver chloride. Depending on quantity, you want to go lye/sugar, or better iron/sulfuric. For Fe/H2SO4, you need to construct the system for continous tumbling of iron and AgCl. So maybe classic ca 20L bucket in cement mixer, or some more sophisticated turning system similar to standard drum-ball mill. Lye/sugar also need mechanical stirring, for both conversion to silver oxide and reducing of silver oxide with sugar. In bigger quantity, lye/sugar can become impractical. But with good stirring and temperature management, you can push it maybe to 10kg for a batch, but I never processed more than 2 kg batch.
 
Several hundred grams, let's call it 500 grams. 2/1000 as gold. So you are getting burnt out over 1 gram of gold? At today's prices that is worth about $60.

I'm just sitting back having my coffee. We both have tried and tried to explain this. I even did a breakdown of the number in the very beginning. I have ask question after question without any clear or concise answers that could give clues to efficiency. I bet he's getting burnt out. On the equipment issues he seems to follow pretty well, but when it comes to the processing he's still chasing ghost. The thought has crossed my mind that either he is the manufacturer of the equipment or knows the manufacturer pretty good and we are doing nothing, but feeding the monster here.

Fine don't take our advice. I'll just have my coffee everyday and read the stories until they come to a logical conclusion of the end. Ignore me until you're broke.
 
orvi said:
In bigger quantity, lye/sugar can become impractical. But with good stirring and temperature management, you can push it maybe to 10kg for a batch, but I never processed more than 2 kg batch.
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For my scale size using 55 gallon drums 25 lbs per batch is a good number. I've pushed bigger lots, but it becomes a P.I.T.A. past that. That's when i go to multiple barrels to process bigger lots. 4 drums x 25 lbs = 100 lb lots. I can push 100 lbs a day using that system, 500 lbs a week, about a ton a month. I can do that with 100 sq ft floor space.
 
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Ralph,
Nobody has to tell you the value of the often overlooked Silver. From the quantities expected to process at Gold Refineries place and the Silver assay he is looking at upwards of $5,000 a week in Silver value. Yet he is looking for grams of Gold. Kind of like the kid who spills the whole bowl of Cheerios while trying to scoop up the one Cheerio on the floor!
With the relatively small 2 kg a day of Silver Chloride to reduce, redissolve and collect the gold then drop as Silver Chloride again to reduce to 999+ silver to sell he can, by adding a simple process, know exactly how much gold is in the chlorides and recover a sale able product which he can also vacuum cast into kilo bars.
 
The value of silver chlorides is crazy at times. I squeeze the pig until it sequels! If he's buying or processing based on just the gold value the chlorides are a free added bonus. I've ask detailed questions about the cost, profit margins, and other efficiency question with no answers. Like what is his accountablity to the client. I give 99%. That other 1% is mine. I'm not chasing that 1%. It's not worth it to me in cost and time. Now once that 1% adds up from so many lots then i'm chasing it. Numbers numbers numbers! That's what drives my processing. Every thing after that procedure wise is based on value both seen and unseen. I don't know if he can't give those numbers or if he don't want to give those numbers. There's a difference. He came here for processing information chemical wise and that's fine, but unless you can see and understand the operation as a whole that alone will not guarantee your success.
 
Having never ran more than 1/2 ounce of karat gold at a time even I know that silver chloride can hide quite a bit of gold. I learned this early on by processing gold filled. I have settling “tanks” or beakers where I leave my wash fluids for extended settling periods. Out of boredom and curiosity I decided to run a small batch and see what was there. Using a 100ml beaker I managed to recover just shy of .1 gram of gold. All this from a 1L beaker with enough material to still be able to see light through it. I also learned that day that not all gold filled is made up of base metals. I have over three gallons of silver chloride to process now and I have no idea how much that will produce in silver metal, but it is going to be an interesting learning experience.
 
Although I have never needed to know on a lot by lot basis the gold quantities hiding out in the Silver Chloride unless the lot loss exceeded 0.25%, I never had to chase it daily. But I also did a lot of refining in the time, After the Hunt Brothers made Silver hit $50, when Silver fell to $3 an ounce. But today, when it averages $21 $22 an ounce and you can generate 50 to 60 ounces a day, a small operator in the same or similar position as the OP could set up a dedicated hood with a tumbler for sulfuric and iron to reduce the dirty chlorides to metal. A bucket to digest the metallic silver (stainless steel, it doesn't break) and a buchner funnel with a vacuum to filter out the gold that was trapped in the chlorides. Then add chlorides (salt or Hydrochloric Acid ) and filter it out. Rinse it well and reduce with the caustic and sugar to yield high purity silver. Start to finish, this would take an employee maybe 3 or 4 hours total. And the quick turn around of the "lost" Gold, combined with the "found" income of the Silver would likely pay the salaries of a 4 or 5 man shop.
Then the OP can rest easy, knowing the accountability within 24 hours of finishing a lot and accounting for all of the gold. Then he can, maybe, answer some of the valid questions members have asked to add even more value to this series of threads.
 
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I would think 50 to 60 ounces of silver would be the economical way to go versus 1/4 percent of gold. Based on shear volume of material run and volume of silver chloride recovered it makes sense that the tiny bit of missing gold would most likely be in the silver. But for .25% I would move on. If time is money, that little bit is very expensive to chase.
 
Truth be told at the quantities the OP is expecting to process major refineries would quote him 1 or 2 dollars an ounce incoming and 99.9 to 99.95% accountability. So less than the 0.25 that is an acceptable loss. Even though it isn’t truly a loss it is more a deferred payment as most of it is found later. Of course they will take a few days to sample and assay but advance you 90% of the value on XRF results and you pay interest on that money until the job settles. So really the majors are more bankers than refiners.

That means there is a reason it isn’t shipping out and I suspect it is the high Cadmium. There are penalties at most majors for Cadmium and above 1% they won’t even accept it.
 
What ever it is holding it back my next question would be how to deal with it. If it is cadmium then that is my target for removal.

Would an xrf not detect the cadmium upfront?
 
Shark said:
Would an xrf not detect the cadmium upfront?
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An XRF absolutely would pick up the Cadmium in the unrefined alloy coming into the refinery.

But there are multiple reasons why people choose to refine on a smaller scale so we will always see refining operations like this thread is about popping up.

Given the rates that this quantity of material can be refined for, I would have invested in a furnace to melt the entire lot in one melt and gotten a bag house to catch any particulates coming off the melt (Cadmium) and melted the lot and, using flux and oxygen sparging, cleaned up the incoming alloy. The precious values and copper will not oxidize out of the melt and the Iron, Cadmium, and Zinc in the alloy will either volatilize (hence the bag house) or oxidize and be in the slag. The remaining metal can be cast into bars and shipped to major refiners without incoming penalties for the Cadmium.
 
So if the material is properly melted into shot it could remove much of the base metals (including cadmium). Is there any good reason for not melting it before processing, especially since it seems to provide a beneficial step in the over all goal of purifying the gold.
 

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