consolidation of Loss Gold thread

[Gold.refinery]

In big drum connected to filters, pipes and condensers, there is plenty of opportunity to lose gold. As 4metals said, half a cup of pregnant liquid will make you unacceptable losses you are experiencing. Altough this is only one of the possibilities where the gold can be. As we all suggested, follow the route of the gold, stepwise from part to part in you apparatus and rinse every part clear with water. Then test this water with stannous chloride to make sure it is gold-free.

My opinion on this is, that the loss will be a puzzle of more than one or two failures or hidden faults in the process. We already debunked incomplete precipitation/sedimentation and find around 3,5g of lost gold. That is promising thing. Now, it is time to find other faults.

From my view, there is maybe one strange question: do you wash your tumbler and filtering apparatus after every use ? or you left them as they are and proceed with another dissolution ?
If you do wash your system, gold trapped in the way will come out in washes. If you do not wash all the piping, it will stay there to the next run. This will make a huge difference in output.

Because we are conducting pilot operations to gain experience, we wash the filters and paths that may contain gold each time.

We got a better result in the last operation. Approximately 6.6 grams of gold was not obtained in 2900 grams of feed.
But we still have a lot of questions, I did not ask them to go with the 4metal way.
Our basic information seems to be flawed.

 

[orvi]

Help me make different samples to test the tin .. !!!

I do not understand why you want to test tin, but I assume you wanted to test gold with tin (II) chloride. Correct me if I am wrong.

It is wise to take one afternoon and get familiar with stannous chloride test. It´s quick, cheap, straightforward and work to quite a dilution (good test can catch 0,1g/L gold, if trained eye is watching).

Firstly, prepare stannous chloride testing solution with recipee posted before here. Store it in airtight container - because oxygen in the air will slowly decay the solution.

For learning and "testing the stannous testing solution", it is necessary to have one standardized gold solution to prove the test is working. Remember, you will only use one drop at the time = you do not need half a liter of it

Take 0,1 g of gold and dissolve it in AR. After completely dissolved, adjust the volume of the solution to 100 mL. Voilá, you now have 1g/L standard gold solution. I will also advise to pipette like 1mL to two separate vials, and adjust the volume to 2 mL and second to 4 mL, respectively. These will produce solutions with strength of 0,5g/L and 0,25g/L. Test these "surely gold containing" solutions with stannous test and observe the reaction. You will clearly see the strong violet-black reaction of the 1g/L solution. As the concentration goes down, colour will be more violet and below 0,25g/L slowly start to vanish. Opposed, if you test the pregnant solution straight from the reactor, you will get completely black, very dark test - because concentration is very high, far more than 1g/L.
You need to see this with known standard solutions BEFORE you will test the real life refining solutions and rinses.

 

[orvi]

Because we are conducting pilot operations to gain experience, we wash the filters and paths that may contain gold each time.

We got a better result in the last operation. Approximately 6.6 grams of gold was not obtained in 2900 grams of feed.
But we still have a lot of questions, I did not ask them to go with the 4metal way.
Our basic information seems to be flawed.

I am happy to hear that your operation is improving. We will slowly work it out. Gold cannot hide, it´s there somewhere, waiting to be found

 

[orvi]

Stannous chloride solution made by machinery manufacturer in our refinery.
He has given us white powder.
He dissolved 50 grams of that white powder in 2 liters of water.
I do not know if it is true or not?

White powder will probably be solid stannous chloride dihydrate. This compound isn´t the most stable compound ever - it slowly hydrolyses and emmit HCL, transforming to hydrated tin oxides. But it takes some time.
I will ask for fresh batch, and test it with standard gold solution described above. If it give you dark violet-black colour, it´s a good testing solution. If the result will be faint violet or no reaction, abandon this "white powder" and make your own one

 

[Gold.refinery]

If the silver chloride isn´t snow-white colour, there is very high possibility gold in tumbler produced dust that is mangled in between AgCl.
Easiest way is to dissolve AgCl in ammonia. But I must point out that for large scale this is far far from good technique to recover lost gold. You need quite a bit of ammonia to dissolve silver chloride cake.

For large scale I would advise to fully dissolve the gold. Make some AR, put it together with AgCl and let it react till there is no gold left in the cake. You can then filter the reaction and recover the impure gold, which could be added to the start of the next batch.

But as test for AgCl locked gold, it´s a very good thing to use NH3. Firstly, you need to be sure no gold solution is present in AgCl and that it is rinsed COMPLETELY from the gold solution. Do not add any water or do not use a dripping wet sludge - solubility of AgCl sharply decrease with ammonia concentration going down.
Take a sample (like a teaspoon) to the beaker, pour few mLs of NH3 and stirr. Eventually, with slow addition of NH3 and stirring, all AgCl should enter the solution - which should be colorless, if AgCl was pure. If any gold is present in AgCl - it won´t dissolve and left as precipitate in the beaker.

If this is the case and you have leftover gold in AgCl, than i bet there will be significant portion of the lost gold percentage. Inform us how it went.

To recover gold trapped in silver chloride, I am looking for a large-scale method, I hate ammonia very, very much. Each method must be such that it can be used many times, not just once.

to drop a large amount of silver chloride into the AR, then filter the solution and take the gold.It seems good. Do other people agree?

 

[Geo]

Prepare your gold standard first. It should be on hand. 4metals gave you the formula to make your stannous chloride.

2 grams stannous chloride crystals
1 gram of tin metal
40 ml of water
5 ml of hydrochloric acid

All of these ingredients for 40ml's of solution. The formula that you gave has roughly half the weight of stannous chloride crystals per same volume of solution than what 4metals gave. I would say that it would be insufficient.
Once you have you test solution and gold standard, then you will no longer be refining in the dark.
Threat the silver chloride with hot AR to dissolve any wayward gold. Filter the silver chloride and rinse well. Denoxx and precipitate any gold from solution.
In between here and there, some AgCl may dissolve. It will be very little over all. If you allow the solution to cool completely and then chill the solution, nearly all of the silver will precipitate as AgCl again. By the time you filter, there should only be a trace of silver chloride left and that will filter out. There's nothing to it more than that. If the solution contains no gold, you can rule the AgCl completely out. If the lost gold is there, you can figure out how to change some thing to stop the gold getting trapped with the silver.

 

[4metals]

Stannous chloride solution made by machinery manufacturer in our refinery.
He has given us white powder.
He dissolved 50 grams of that white powder in 2 liters of water.
I do not know if it is true or not?

Making the stannous chloride up 2 liters at a time is just too much to have prepared and inviting it to go bad.

The formula I gave you, one of many that work, is made up to a volume of 45 milliliters. When you test with stannous chloride you use one drop to test. So the 45 ml as I suggest will give you about 900 tests. That will last you for a while. The 2 liters will give you 40,000 tests! It will go bad by the time you have used it up.

If you notice the formula I prefer has metallic tin and hydrochloric acid. While the powder you have (assuming it is stannous chloride) will produce a stannous chloride solution, there is little done in the way of preserving the solution for longevity.

Tin chloride has a stannous form and a stannic form, stannous works for us and stannic doesn't. Aqueous solutions of stannous chloride undergo hydrolysis which is why they go bad. The tin added to the solution helps prevent this oxidation. So the addition of the Hydrochloric Acid and the Tin metal acts as a preservative.

Another trick useful for stannous testing is useful for dirty solutions. Often with low concentrations of gold in solution, a dirty solution being tested will mask the result. To help overcome this, place a few drops of the dirty solution on a paper towel and a few centimeters away place a drop of your stannous chloride testing solution. The paper towel will wick the liquids outward and any particulate in the dirty sample will remain behind as clearer solution migrates outward. By placing the drops a few cm apart, they will merge as cleaner solutions and when they touch, usually in less than a minute, the reaction is easier to see. Just focus on the leading edge of the migrating liquids and look for the reaction to indicate the presence of gold. You are likely to encounter dirtier solutions if you start testing your cemented solutions so it's a good trick to keep in mind.

 

[4metals]

Discolored Silver Chloride can be from other things like exposure to light. Generally there are 2 things to look for in the silver chlorides on the filter. First and foremost the chunks. If you make the prescreen I described earlier those chunks will be easy to rinse and collect leaving you with the fines of Silver Chloride which are sitting on the filter paper. These chlorides can also contain gold but usually it is low enough to collect the chlorides and process them in bulk.

In a production environment it is typical to look for a recovery of 99.75% or better. If you get that you can assume the balance is in the chlorides and collect your chlorides for recovery later. I am not a big fan of ammonia for dissolving chlorides either. I would go with either the caustic sugar route or reducing with iron. Either way it is better to accumulate them if your yields after considering the gold content recovered from the process plus the gold content by assay in any chunks removed from the Silver Chloride and cleaned and melted into a button for assay, is up to your expected yield. (99.75%)

 

[4metals]

to drop a large amount of silver chloride into the AR, then filter the solution and take the gold.It seems good. Do other people agree?

You are trying to dissolve the gold that was trapped in the silver chloride on your first attempt with the same acid that trapped it the first time without doing anything to release the gold trapped. The silver chloride is not soluble in aqua regia so this method will not work.

I suggest either the caustic sugar approach or the iron reduction. Either will work. Either will produce silver metal which can be dissolved in nitric acid to release the trapped gold. Once filtering out the gold, you can drop the silver again with Hydrochloric Acid or salt and filter out the white fluffy silver chlorides. These can be well rinsed and reduced to high purity Silver using the caustic and sugar method with a lot of rinsing.

The first reduction will produce metallic Silver which can be dissolved to collect the remaining gold from the karat dissolve. The second dissolve will yield Silver Chloride which the caustic sugar method can be used to give you a saleable Silver.

 

[4metals]

You guessed it, acids are added from the same tube, but water is not added from there.

Some of the systems add water through that duct as well as acids. It can be problematic because you cannot see into reaction vessel and you may add too much.

You said not to add extra water to the reactor before filtering, why?
Instead of adding ice, we have 2 Celsius water. And add some before filtering.

The goal here is to get the solution as cold as you can to keep the silver out of solution. Your method has you adding a prescribed volume of water which cuts your acid (and gold) concentration in half. Ice will accomplish the cooling without the volume.

The reason I do not suggest adding too much water is you will be adding water to rinse out all of the reactor and pipes as well as the filter so you will end up with a lot of waste to deal with. The ice does the job cooling the liquid. I would next be filtering the cooled acid and then rinsing the reactor clear.

The spinning reactor has a large port on the cylinder which is opposite the drain port. Once the iced liquid has been filtered, remove that cover, rinse the acid on the inside of that cover into the reactor, and look straight down to the drain port on the opposite side of the reactor. You will see a crescent shaped pool of acid that is concentrated acid, with gold. This is because it is near impossible to fabricate the drain exactly at the bottom of the vessel to drain completely and the space between the drain hole and the bottom sitting at the angle of the rotating vessel, creates the small crescent shaped pool I described. Rinse that pool of acid until it is clear and using a wand you make to spray inside the reactor, use water to rinse the inside of the reactor completely. This will assure you have gotten all of the values into the filter below. This should also use less water than a 50% dilution with cold water followed by a rinse. For waste treatment later this will be important.

From here rinse the filter holding the silver chlorides until it tests negative for gold and pump the filter dry. When you remove the filter media to collect the chlorides, open the top of the filter and make sure all of the surfaces are rinsed through the pump.

Now we are of the assumption that all of the values, except those tied up in the chlorides, are in your precipitation tank and are ready for your precipitation.

Please send a photo of the tank you use for precipitation and describe the method you are currently using to drop the gold.

 

[Gold.refinery]

We have 3 of these tanks.
The first tank is for precipitation of gold.
Then the mother solution is transferred to the second tank after the gold is filtered (here the gold remains on the filter).
It stays there overnight and then filtered into the third tank (here the sludge contains copper and the rest of the gold left over from the previous stage).

Each tank consists of two valves, one at a height of 17 cm, one at a height of 7 cm from the floor) The second fir little solution).
There is also a big valve on the bottom of the tank for final washing.

A tube with air flow is used manually to completely dissolve the solution and mix it.

 

[nickvc]

If the OP had only done one process then any solution trapped in the reaction vessel could explain his lose but I believe he has done three all with similar loses on each one , so to my mind if there are no lose to the fume extraction then it would logically be from filtering onwards.
We know there is some gold trapped with the silver chlorides and in the settlement tanks and I suspect because he is dropping everything that the main lose might well be hidden there amongst all the base metals, how is that material been assayed as if it’s by xrf it may well be wrong.

 

[Gold.refinery]

If the OP had only done one process then any solution trapped in the reaction vessel could explain his lose but I believe he has done three all with similar loses on each one , so to my mind if there are no lose to the fume extraction then it would logically be from filtering onwards.
We know there is some gold trapped with the silver chlorides and in the settlement tanks and I suspect because he is dropping everything that the main lose might well be hidden there amongst all the base metals, how is that material been assayed as if it’s by xrf it may well be wrong.

Our losses have not been the same in three operations. The first operation is 27 grams out of 2700 grams (by accident), the second operation is 12.6 by 2610 grams and the third operation is 6.6 by 2900 grams. I can explain the differences of each operation, we added the sludge from the second operation to the feed of the third operation.
I agree with you about concentration on Filters.
You guess most of the gold is lost in the base metals, is this because of our use of hydrazine for sedimentation ??

I did not understand what you meant about our wrong analysis with XRF.

 

[4metals]

I think filtration here is a big part of the issue. First thing is there are a good number of manufacturers selling tumbler systems and from my experience they provide the equipment, provide a poorly written description of its operation, and pretty much leave the proud new owners of the equipment on their own.
I do not understand why, after using the filter to filter the dissolved alloy in the tumbler, they feel there is a need for an in line filter. You either filter properly or you don't. On thinking about this, and going back over the photo's, and what I know first hand about other tumbler systems, there are a few things amiss.
In this photo provided by the OP, the grid on the bottom of the filter has some rather large openings. The OP has said they use a reusable fabric filter on this filter. He did say the filter is held in place with a gasket so I assume nothing leaks around the filter. But from what I know about these filters, if the openings are too large, as these are, there is a necessity to put a fabric over the grid to prevent any filter sheets from sucking into the holes. I believe the screening the OP is using is intended to support the proper filter papers placed on top of the reusable screen. And by not using any filter media other than that screen, silver chlorides will definitely pass through the filter. What is the mesh size of this reusable screen can Gold Refinery provide us with that information, and possibly a close up photo of the screen? If the filter is working as intended it should not require a downstream spiral wound cylindrical filter.

Secondly, they drop the gold in one of the tanks, again filter it, and then store it in another tank to, as Gold Refinery put it

The first tank is for precipitation of gold.
Then the mother solution is transferred to the second tank after the gold is filtered (here the gold remains on the filter).
It stays there overnight and then filtered into the third tank (here the sludge contains copper and the rest of the gold left over from the previous stage).

Again, if the filtration is proper, the gold precipitates should be in the filter, not beyond. A well designed refining plant puts all of your values (within reason) in one place and shouldn't leave the refiner chasing all over the process equipment looking for lost values. Gold Refinery, a close up photo of the grid on the filter and of the reusable screen you place on top, I think this is an issue we need to correct.

A tube with air flow is used manually to completely dissolve the solution and mix it.

Bubbling air is not an effective mixer with something as dense as gold. It's great to move solutions but when precipitating gold there is something that happens when you drop a lot of gold that most do not realize. When you have the air bubbling and start dropping your gold, as the gold drops, it is blanketing the bottom and actually remaining surrounded by gold in solution that becomes trapped under a few inches of precipitated gold mud. Since a column of air bubbles will not effectively lift the gold off the bottom, the solution mixed and trapped under the precipitated gold can not react. You finish adding your precipitant, test with stannous, and assume all of the gold is dropped. Except there is gold in the solution trapped by the gold sponge that has not been properly exposed to the chemistry you are using. Remember we discussed just how much gold a small quantity of aqua regia can hold, this can be significant in your case.

The fix to this is to physically use a wide blade paddle to physically move the gold sponge you have precipitated and allow that solution to also react and drop its gold. Most systems have a large blade mixing motor to assure good movement of the gold as it drops and keep it moving to avoid this issue. Your air bubbler will not accomplish this.

When you transfer to the next tank, that solution which still has gold in solution, reacts with the chemistry and drops out. It can pass through a filter when it is dissolved but will drop in the solution it is mixed with in the next tank. Possibly that is why there is a second tank. To use an a
American phrase, that is Mickey Mouse! To fix it, agitate properly to assure complete precipitation and filter it properly and it will all be where you expect it, in the filter.

Everything we have touched on thus far reflect on the operation of the physical equipment, not your choice of chemistry. Send photos of the grid and the screen to help figure this out.

I did not understand what you meant about our wrong analysis with XRF.

XRF is often mistaken on sludges or powders and without proper sample preparation and the proper algorithm running on the software, the answer spit out by the same XRF you used to analyze the karat scrap is not to be believed.

 

[4metals]

These are images from another system. This is the smallest system I have ever worked with, I have photos of larger ones but these will suffice as an example. This is the tank where the gold is dropped and it is filtered. Basically they are all simply raised tanks which allow a filter to fit beneath. They usually have a slightly coned bottom to allow complete drainage, and some type of effective mixing. The photo on the top left shows the gold rinsed and sucked dry on removal from the tank, to it's right is the tank with the filter seen below. The next photo is just the system at another angle, and the last shows the mixer blade which is permanently fixed in the tank.

 

[4metals]

This is another photo of a filter showing the removable grid and the tools to remove the grid. The 2 circles sticking up are supplied to fit into slots made to simplify lifting out the plate to rinse it completely. These holes are 5 or 6 mm in diameter, smaller than in the grid shown by the OP. This manufacturer supplies 2 grades of filter paper, the heavier is rather rigid like thin cardboard and it does not necessitate using a reusable screen below it, the thinner paper is actually what most consider filter paper. Without a screen mesh below it to support it, it will be punctured by the vacuum and allow solution (and solids) through.



compare these holes to the holes in the OP's filter.

 

[orvi]

Point with poor mixing during the drop is very concerning. I will definitely try to check that and stirr manually, if there is not any overhead stirrer available. Also, gold powder in thick layer is hard to stirr with lower power stirrers. It tend to collect around the walls and stay there.

It will be then easy to check the solution that passed filter for any soluble gold. 5 g in 25 liters is detectable with stannous without much problems.

 

[4metals]

It will be then easy to check the solution that passed filter for any soluble gold. 5 g in 25 liters is detectable with stannous without much problems.

In a perfect world, absolutely true about the sensitivity of stannous chloride. But the circumstances here are different. Let's say enough liquid containing gold was trapped under the gold sponge to hold some gold. The solution mixing above it will test negative so you might not even realize it is there. If you use a paddle to mix it up, the time between the solution being trapped and the solution being exposed to the liquid above, likely with enough chemistry to reduce the newly exposed gold, will often drop the gold quickly. So even stirring will not indicate it.

if you didn't stir it, or stirred it inadequately, the liquid gold would go through the filter and the rest of the solution and reducing agent will follow behind, reducing it to metallic gold where it will not be indicated by stannous and settle to the bottom. (along with any other crap on the bottom)

So this system makes it difficult to actually prove the gold was there easily but by design it is inherent. The cure is adequate mixing.

The reason I said most don't realize this phenomenon is because it is possible only when dropping a lot of gold so the dropped gold forms a dense thick layer in the vessel trapping pregnant solution beneath it. Few of our members deal with these quantities of gold to ever notice it.

 

[Gold.refinery]

You point out the problems carefully, thank you. But according to our conditions and the design of our device, please also provide the best solution available.

I agree that the person who sells the device does not provide the proper training and may not be able to provide it.

From the last operation, we use two filters at the same time, a fabric filter on the lower grid with the rim fixed, and a paper filter on the fabric filter. With this technique, we got better results from previous operations.

Can you provide us with the specifications of a suitable paper filter? (Due to the problems of our filtration system compared to italimpant)

The manufacturer of the device explained the reason for using the cylinder filter to better filter silver chloride, but if it wants to cause a problem, it can be removed from the way.

I do not know the size of the fabric filter mesh.

You said that silver chloride passes through a fabric filter. If it is filtered correctly, there is no need for a cylindrical filter.

You do not need a second bunker to filter gold if it is filtered properly.

I agree that values should be concentrated in one place, not several places. One place but correct. Not a few unsafe places

I will send photos and videos of the filter, network, fabric tomorrow.


Due to the lack of a suitable mixer, the amount of gold-containing solution is trapped under the deposited gold sludge and prevents the precipitator from reaching. The bubble does not work. Only physical displacement. What is the best solution to this problem with our tank conditions?

I noticed that the sludge and powder test with XRF is faulty. For two reasons: software standard, heterogeneous sample.

 

[Gold.refinery]

We have already learned how to calculate the amount of acids from you.
But we add the ingredients to the end, including: water, urea, precipitate, flocculant, aluminum,….

What will be the ratio of these substances to the raw food?

Knowing these ratios removes the operator from doubt.
Seeing reactions and recognizing the amount of material is difficult for a beginner. (No experience)