Waste treatment system at Gold Refinery

[4metals]

This thread has been broken off from the Gold loss thread at Gold Refinery specifically to address the waste treatment system they have.

I assume you are treating your waste with a process known as classic destruct. This involves adding caustic liquid to the acid waste until the metals. in solution are converted over to. metal hydroxides

Our classic filtration system has 4 stations with the method of adding caustic soda according to the image.
The first station has a motor mixing with the blade. In the first station we add AL.

The second station has pipe with air injection.

The third station has a motor mixer with a dosing pump to add caustic soda.

The fourth station is for final maintenance and control only.

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[4metals]

Finally, the liquid goes by a diaphragm pump to press the filter.

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[4metals]

Our classic filtration system has 4 stations with the method of adding caustic soda according to the image.
The first station has a motor mixing with the blade. In the first station we add AL.

It is excellent that you have a cementation tank built into your system but I question why you are choosing to use aluminum to drop your values? There are many threads on the forum about electromotive series and what metals effectively displace others in solution but for your first tank, I would be cementing with copper. If you cement with aluminum you will drop all of the copper, zinc, nickel, and any remaining gold or platinum group metals. If you cement with copper you will be dropping only Gold and Platinum group metals (and technically mercury but I doubt it's even present). This process will yield only values and some excess copper and all of the base metals will pass on to tank 2. This would also be a good place for the canister filter because any small fines pumped out of tank 1 with the liquids you want to keep.
Tank 2 should have the pH raised slightly with soda ash and you can add scrap iron to recover all of the copper in your solutions.
Tank 3 is where you add liquid caustic to a pH of 10. This will drop all of the metals as hydroxides. These hydroxides are collected in your filter press and the liquid from the press goes to tank 4 where you will likely need to lower the pH to discharge to sewer.
The tank where you add caustic can actually also drop all of the metals remaining in your waste including copper if you choose to skip the iron step. If you did skip the iron step, the best use of the tank space would be to fill the first tank with waste acid and add the copper with mixing. Continue to mix until you start to fill tank 2 with the same waste to be cemented with copper. When you are getting close to filling tank 2 shut the mixer in tank 1 so it can settle overnight and test to be sure the metals have dropped. I the morning tank 1 can be pumped into tank 3 for hydroxide precipitation. By using the first 2 tanks for copper cementation you can maximize the time exposed to copper and get the best recovery.

This is a very old thread about dealing with waste but it uses the same concepts you will use so it may be a good read.

Dealing with Waste

 

[Gold.refinery]

but I question why you are choosing to use aluminum to drop your values?

Add aluminum suggested by the manufacturer.
Of course, I have to remind you that when we filter the gold in the settling tank, we transfer the mother solution to the secondary tank (this tank is not from waste treatment stations) and we add aluminum there.
Copper sludge was then deposited on the bottom of the tank (as shown). Then we filtered the solution to the first waste treatment station. Most of this sludge is copper, but it also has some gold.(Approximately 5-15/1000)

Are we allowed to add this sludge to Tumblr for the next operation?
In one of the previous operations, we added that sludge to the Tumbler for the next operation. The result of the unearned gold improved in the end (6.6 / 2900 g). Not sure if this is true or not?

 

[Gold.refinery]

I read your description of stations 1 to 4 several times. I did not understand some of them clearly.

Suppose we filter the solution after taking gold and we have 50 liters of solution.

I would be cementing with copper.

Suppose we filter the solution after taking gold and we have 50 liters of solution.
How much copper should we add first?
(Cu powder :This copper can be obtained from previous operations with iron, right?)

If you cement with copper you will be dropping only Gold and Platinum group metals

how to filter precious metals if they have precipitated?(will be very little)

Tank 2 should have the pH raised slightly with soda ash and you can add scrap iron to recover all of the copper in your solutions.

Why should we raise the pH with soda ash?

This would also be a good place for the canister filter because any small fines pumped out of tank 1 with the liquids you want to keep.

I do not understand what you mean by conister.

Tank 3 is where you add liquid caustic to a pH of 10. This will drop all of the metals as hydroxides. These hydroxides are collected in your filter press and the liquid from the press goes to tank 4

By adding caustic soda we increased the pH to 8. 10 is better?
Can it be transferred to the filter press immediately after reaching pH 10 or do we have to wait a day?

If you did skip the iron step, the best use of the tank space would be to fill the first tank with waste acid and add the copper with mixing.

Do you mean that if we do not want to take copper from the solution with iron, use the first and second tanks for cementing with copper for one solution. Both tanks for cementing copper with solution ??

 

[nickvc]

Using copper to cement your solution will reduce the amount of sludge including values that have to be refined which saves money and time, in fact you could quickly dissolve this material separately and recover any values easily making accounting easier , by doing this we can then head backwards in the process to find where any other loses are occurring.

 

[Gold.refinery]

in fact you could quickly dissolve this material separately and recover any values easily making accounting easier

You mean, after we add copper, we can calculate the total amount of gold and balance the accounting. Did I get it right?

 

[nickvc]

You mean, after we add copper, we can calculate the total amount of gold and balance the accounting. Did I get it right?

Yes if you use copper you will have a small amount of material to work with which could be refined or melted to confirm how much gold is there… the other point I made is if you can confirm the lose there any other loses should be before this .

 

[4metals]

Gold Refinery, I think you want to make money refining, correct? You will never do that if you go off looking for every gram of gold that doesn't come out of your process lots. As I said before, with all of your equipment issues patched up, you should be able to achieve 99.75% accountability on all lots. Then the gold that is retained in the silver chlorides is not chased for every lot, it is processed when the quantity warrants or the production schedule allows. Same is true for the dilute quantities of gold you have cemented in your waste treatment.

The tumbler plant is not designed for low grade, low yield metallics like the cemented sludges you get from the aluminum cementing. If you use copper, it will be much more concentrated and almost exclusively precious metals in your tank. But not enough to recover from every batch.

By adding caustic soda we increased the pH to 8. 10 is better?
Can it be transferred to the filter press immediately after reaching pH 10 or do we have to wait a day?

Depending on what metals are in your waste you select the proper pH to drop your hydroxides. pH 8 is a good starting point. If the liquid emerges from the press anything but clear, raise the pH in a bucket of water from the press slowly 0.5 pH units at a time and see if more hydroxides drop. There is a graph showing pH vs metals dropped which I will find and post here (if and when I find it). It only allows metals to redissolve if you wait too long to press it, especially if you used urea so I would press it quickly.

 

[silver1]

I seen him mention hydrogels in another post. Is he using hydrogels, caustic, both?

 

[4metals]

From this you can see that copper will be out by pH 8 but zinc and nickel around 10. also note that zinc starts to go back into solution if you go up above 10 so don't over add either.

 

[orvi]

Add aluminum suggested by the manufacturer.
Of course, I have to remind you that when we filter the gold in the settling tank, we transfer the mother solution to the secondary tank (this tank is not from waste treatment stations) and we add aluminum there.
Copper sludge was then deposited on the bottom of the tank (as shown). Then we filtered the solution to the first waste treatment station. Most of this sludge is copper, but it also has some gold.(Approximately 5-15/1000)

Are we allowed to add this sludge to Tumblr for the next operation?
In one of the previous operations, we added that sludge to the Tumbler for the next operation. The result of the unearned gold improved in the end (6.6 / 2900 g). Not sure if this is true or not?

As it was said, aluminium is rather unselective precipitant, if you are trying to scavenge last bits of values out of waste solutions. It will even precipitate cadmium out.

We usually use copper bars hanged into the solution, but copper powder will also work, if stirred properly and constantly. Powdered metals gave you advantage of very quick cementations, if stirred good - due to great surface area.

I sometimes encounter the need to concentrate dilute values (AuAg) - say 0,3-0,5g from 3 liters of solution. In these cases, I add like 10 grams of copper powder to the stirred solution and let it mix for like one hour. Then I filter the solution and redissolve the powder in AR.
You can also use the same principle, but stirring is necessary.

Eventually, if you add aluminium, all the nickel, copper and also the gold will precipitate. What happen next is that good portion of the less reactive metals like nickel or iron will cement out even more copper - simultaneously passing to the solution as ferric or nickel ions. Sounds good, you say, I create copper in the solution, that´s what I wanted - but you will precipitate awful lot of metal sludge which needs to be processed AGAIN.
Your intention is to GET RID OF THE BASE METALS, that is why you refine the gold. Not to just stick aluminium to the precipitation tank to get them back and repeating the process one more time, with values even more diluted.

 

[Gold.refinery]

Same is true for the dilute quantities of gold you have cemented in your waste treatment.

After the end of each operation, if we reach 99.75 incoming gold, we can hope that some gold is in the mother solution and also some gold is trapped in the silver chloride.

It is probably wise to recover silver chloride every two weeks, but it is not possible to keep the mother solution for more than 4 or 5 days.

But not enough to recover from every batch.

So what to do with these conditions?

We are currently using urea temporarily, so after seeing the metal hydroxide in, it should be transferred to the filter press immediately.right?

Finally, There we have green sludge (as shown).
What should we do to recover the precious metals of these this Hydroxides ?
(Shall we give it to the recycling workshops we go to every month with Smelting method?)

 

[Gold.refinery]

I sometimes encounter the need to concentrate dilute values (AuAg) - say 0,3-0,5g from 3 liters of solution. In these cases, I add like 10 grams of copper powder to the stirred solution and let it mix for like one hour. Then I filter the solution and redissolve the powder in AR.

So we have to dissolve about 200 grams of copper powder for 50 liters of solution and we have to stir well for an hour.
But our tanks does not have a mixer, unfortunately, but it has a filter at the bottom.

The first waste water tank has a mixer but not has filter.

What should we do with these conditions?

 

[FrugalRefiner]

Take a look at When In Doubt, Cement It Out. At the end of the post, you'll see a cementation rig used by one of 4metals' customers.

Dave

 

[orvi]

You need to agitate somehow the solution around the copper. This will speed up the process rapidly. If you have no chance of getting mixer, forgot the powdered copper and use copper sheet or bar. And use air bubbler to circulate the solution around it as suggested in thread When in doubt, cement it out as Dave suggested.

 

[Gold.refinery]

You need to agitate somehow the solution around the copper. This will speed up the process rapidly. If you have no chance of getting mixer, forgot the powdered copper and use copper sheet or bar. And use air bubbler to circulate the solution around it as suggested in thread When in doubt, cement it out as Dave suggested.

Thank you very much for your support, it is very helpful

 

[silver1]

It is probably wise to recover silver chloride every two weeks, but it is not possible to keep the mother solution for more than 4 or 5 days.

Why? Also how much materials are we talking about do you run in a weeks avg. Are you running 25 kilos a day. week. month? What volume are to trying to run avg?

Keep the chlorides wet and don't let them dry out. Especially keep them away from that ammonium you have been using.

 

[Gold.refinery]

Finally, There we have green sludge (as shown).
What should we do to recover the precious metals of these this Hydroxides ?
(Shall we give it to the recycling workshops we go to every month with Smelting method?)

 

[silver1]

I don't know about laws where you live, but if you can't sell it then you are going to have to have to pay to have it carted off. If you can find a way to dispose of it for free i would go with that. Waste is a negative in this business. I used to go the route you are now. I then found a licensed waste disposal company that would take mine for free for the metal content. Win Win far as i'm concerned. That's also the reason i ask you about why you couldn't let processed solution build up more than the 3-4 days as you said. Here i'm only allow to store so much waste until i pass a threshold and then i'm in violation territory. One trick my state EPA allows is to classify my waste as IN PROCESS, not storage. My cementation tank where i hold my waste solution is not classified as IN STORAGE, because it has air bubbling through it and copper hanging in it circulating while the process continues. It has an evaporator and when it's time to empty you suck it out like an old septic tank. The waste tank is a continual process for me, NOT a batch process. Two things never get shut down in my shop. The fans and the waste tank.

ALL you values should be removed by this point. I've never specifically processed hydroxides for value after going through my system.