# Processing nitric waste before disposal



## autumnwillow (Jun 22, 2015)

Hello, 

I will be processing my nitric acid waste from inquartation. I just use silver and a little bit of copper. The inquarted items are scrap jewelries.

Correct me if I am wrong, the valuable items worth processing here is only silver and palladium.

I will be using salt to make silver chloride and process it further with caustic, dextrose and heating. (Some will go for inquartation again and some will go to electrolysis-which i still have to research on)

How about palladium? I've been trying to search the forums on how to precipitate palladium but can't seem to find one.
And which one should I process first? Silver or palladium?


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## kurtak (Jun 22, 2015)

First of all how do you know you have Pd in solution - did you test for it with DMG ?

Second I would avoid making silver chloride - you are better off cementing you silver back with copper

as far as parting Pd from silver - first we need to know that in fact there is also Pd in solution (DMG test)

do you have DMG ? do you know how to prepare DMG?

Kurt


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## MarcoP (Jun 22, 2015)

After testing for silver and palladium I would, in any case, cement with copper and part them in a silver nitrate cell. If there is over 5% Palladium I would store the powder and mix it with another lot.
The parted powder via clorox method, just because I believe it's easier to work with palladium in chloride then in nitric.


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## autumnwillow (Jun 22, 2015)

Why is cementing with copper preferred over conversion to silver chloride?

I am just assuming that there would be Palladium. I can make stannous chloride to test, but haven't researched about DMG, I think I have read about DMG somewhere here in the forums.

Does stannous chloride test only work with AR solutions?

Thank you


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## kurtak (Jun 23, 2015)

autumnwillow said:


> Why is cementing with copper preferred over conversion to silver chloride



Because washing all the chem out of AgCl is more time consuming & creates more waste - first you have to wash all the acid out after doing the conversion to AgCl - THEN you have to wash the NaOH/sugar out after the conversion/reduction with those chems = MORE time + more waste

Plus - if you have Pd (&/or Pt) involved it is now going to be in the very, VERY dilute washing out of the acid so you will need to do a great deal of evaporation before going to recovery of those metals

If you cement with copper you get both you Ag & Pd (& Pt) back & ony need to wash the acid (copper nitrate) out



> I am just assuming that there would be Palladium.



Assuming is only going to lead to chasing your tail on something that "might" be there --- that's why we "test" 



> Does stannous chloride test only work with AR solutions?



No - it will work to test Pd dissolved in a nitrate solution - HOWEVER - if silver is "also" in solution it will convert the Ag to AgCl & the AgCl will photo color change thereby masking &/or giving a "false" positive for other metals - which could result in you "thinking" there is Pd &/or Pt in solution when in fact it is not --- that's why DMG is used to test for Pd in a Ag nitrate solution - DMG is a "proof positive" test for Pd



> but haven't researched about DMG, I think I have read about DMG somewhere here in the forums



You have been a member here since 2010 - but it sounds as though you have not yet read Hokes - now would be a good time to do so

In her book she talks about boiling the DMG in water to prepare it - although that works - it does not work well - it works better if you use some NaOH - I can post the water/HaOH/DMG ratio later (will have to look it up - don't know it off the top of my head)

Kurt


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## kurtak (Jun 23, 2015)

MarcoP said:


> After testing for silver and palladium I would, in any case, cement with copper and part them in a silver nitrate cell. .



When running silver that has Pd in it - in a silver cell - only "some" of the Pd stays behind in the anode slime --- some of it goes into the electrolyte along with copper - if your electrolyte gets a green color rather then a copper blue that is an "indication" that Pd "could" also be corrupting your electrolyte

At some point - when the electrolyte becomes corrupted enough with the Pd the Pd will start co-depositing with the Ag

Edit to ad; - doing a "complete" parting of Pd from Ag is not a simple task

Kurt


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## 4metals (Jun 23, 2015)

I have had success removing Pd from a silver electrolyte with DMG dissolved in NaOH. I transfer the solution to a mixed vessel, add enough nitric acid to counteract the NaOH used to dissolve the DMG, and add the DMG directly to the electrolyte.

I do this slowly and always check to assure the Pd is coming out as the yellow salt (easy to do as it is quite visible) and when the additions do not produce a precipitate, I filter the solution and return it to the cell to continue to use the electrolyte. 

This method is effective for maintaining a Pd level in solution that is dilute enough that it will not be plated out with the silver.


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## autumnwillow (Jun 24, 2015)

Dimethylglyoxime or DMG. Seems like a hard to find chemical.

Anyway, if I ever find one and the results return positive for Pd should I precipitate with DMG first before cementing with copper?
Or should I cement with copper, separate thru electrolysis, re dissolve pd in nitric then precipitate using DMG? 

I would really prefer the first method as not all of my cemented silver will go thru a cell, some of them would go to inquartation and I believe that a very small percentage could be lost in the melting.


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## 4metals (Jun 24, 2015)

I would separate it with DMG and collect the salt until you have enough to reduce. 

Then the silver can be cemented with copper and used to inquart again.


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## goldsilverpro (Jun 24, 2015)

autumnwillow said:


> Dimethylglyoxime or DMG. Seems like a hard to find chemical.
> 
> Anyway, if I ever find one and the results return positive for Pd should I precipitate with DMG first before cementing with copper?
> Or should I cement with copper, separate thru electrolysis, re dissolve pd in nitric then precipitate using DMG?
> ...


DMG seems to run about $1/gram, at least on eBay. According to Hoke, it takes about 2.5g, or a little more, of DMG per gram of Pd. Therefore, $10 worth of eBay DMG would collect about 4g of Pd ($89). It's been awhile, but I'm thinking that DMG gets essentially 100% of the Pd out and that the product is pretty easy to reduce. Its biggest problem is that the product is extremely voluminous - a little Pd makes an awful lot of precipitate.
http://www.ebay.com/sch/i.html?_odkw=dmg&mfe=search&clk_rvr_id=855416504707&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R1.TR1.TRC0.A0.H2.Xdimethylg.TRS0&_nkw=dimethylglyoxime&_sacat=0


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## 4metals (Jun 24, 2015)

Cole Parmer sells DMG for $52 for a 100 gram bottle, cheaper still by the kilogram. 
And yes DMG drops all of the Pd. the large volume of the precipitate makes it attractive analytically. 

For the small quantities of Pd I Have experienced in silver cell electrolyte it is worth it. Recovering Pd from Dental is a different story, then I'd use ammonium chloride and sodium chlorate from a nitric free solution.


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## solar_plasma (Jun 24, 2015)

Following this discussion I just came to wonder, if it might be a good way 

first to precipitate by cheap ammonium chloride and sodium chlorate and then to precipitate what's left in solution by DMG? 

Or does ammonium chloride/sodium chlorate precipitate quantitatively from nitric free solution?


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## 4metals (Jun 25, 2015)

Ammonium chloride and sodium chlorate works best in concentrated solutions and still leaves behind a PPM or so in the waste acid. Usually recovered by resins.

But this was a post about nitric waste so DMG would be my first choice.


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## Lou (Jun 25, 2015)

You can also remove most of the Pd and some of the copper by pH adjustment with dilute sodium hydroxide to about 6.5. Then that filtered solution is adjusted in pH back to 2.5-3 which is where you want to keep it anyway to prevent Pd co-deposition.

Or as 4metals suggested, sodium dimethylglyoximate (dissolve DMG in caustic soda, dilute, and use). Test on a sample to determine correct dosing.


There's also a very expensive resin that will selectively remove Pd (and also for Cu) from silver nitrate.


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## autumnwillow (Jul 2, 2015)

I was wondering if I could also precipitate the copper? Drop them, dry, then just save them in a large pvc drum for storage. When the drum is full, melt it then sell it?

According to the reactivity series copper should precipitate with iron, zinc, lead or hydrogen? Am I right? Do I just hang a lead bar in there and then copper would precipitate?

DMG will arrive this week, I will test first in a 1 liter beaker. Ill post pictures. =D


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## FrugalRefiner (Jul 2, 2015)

Most people use iron to drop their waste copper. The Dealing with Waste thread explains it well.

Dave


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## autumnwillow (Jul 2, 2015)

Thank you for referring me to that thread. I'll proceed with the procedures as instructed.


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## kadriver (Jul 12, 2015)

Here is a video that I made that shows how I removed the dissolved palladium from the electrolyte from my silver cell.

The filtered palladium salt is set aside in a covered container until I have a quantity of them, then the Pd salt (filters and all) is dissolved in AR and refined.

I just used hot water to dissolved the DMG, it seems to work fine for me.

https://youtu.be/zU6Wky0Az94

kadriver


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## autumnwillow (Jul 16, 2015)

Uhm. I accidentally dropped a 2kg copper bar in the nitric solution while I was trying to hang it. I can't take it away anymore (too deep) not unless I filter out the solution. Would that be ok? I'm just going to use the silver for inquartation anyway since I have another batch to process for electro refining. Its been bubbling for almost 5 hours now.

After the silver cementation, I will drop the copper using scrap iron then can I just neutralize the acid and safely throw away the solution in the sink?
I tried to compute the price of iron to magnesium hydroxide. I just think that it would be costly to drop iron or could it be that 1 gram of magnesium hydroxide will drop a lot of iron?


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## autumnwillow (Jul 16, 2015)

By the way, has anyone tried using one of bag like filters? Like the one on this site http://www.strainrite.com/liquid-filter-bags.php or vacuum filters? 
I just think that it could be faster than siphoning and filtering.

Basically the idea is to put the precipitant (copper, iron) inside that filter then just pull it out afterwards, leave it hanging for a while then wash with water.


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## g_axelsson (Jul 16, 2015)

The copper bar could be covered up by silver and make the cementation process go slower, but except for that you can pick up the left over copper after the silver have cemented out.

If you would hang a piece of copper with a filter bag then you need to keep the copper away from the bag. The silver cementing out could easily grow through the bag and start to cement on the outside of the bag.
Pumping around the silver nitrate is generally a good idea, but you would probably need to circulate it back several times before all silver have cemented out. Cementation takes it's time.

Göran


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## Palladium (Jul 16, 2015)

Don't know how much silver your dealing with, but don't try and reinvent the wheel. The bag idea will only lead to more complications.

[youtube]http://www.youtube.com/watch?v=8UVK18cAeEA[/youtube]


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## autumnwillow (Sep 15, 2015)

Hello, I'm currently in the process of precipitating the copper.




I was able to recover around 2.2kgs of silver, although the quality is a bit low (see picture). It used up around 3 kgs of copper (I guess there is still a lot of free nitric unused in the solution.) When I was hanging a slab of copper on the solution, the silver was coating it, it was kind of hard but can be removed easily by hand (with gloves). I guess I lack pressure on the air pump?



Anyway, back to the copper. I have 2 buckets of copper nitrate, the other bucket is a little dilute with tap water. The dilute copper nitrate's PH is already 2.5, i added a little soda ash to it, the PH moved to 2.9 but when i added the iron scrap nothing happened. Is this normal for a dilute solution? Maybe I should wait a week?

The other bucket is much more concentrated, I am still in the process of raising its PH from 0.6 to 2.5.


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## butcher (Sep 17, 2015)

After using copper to displace silver and other values (palladium if any).
You should use the iron to displace the copper while the solution is still acidic, adding a base before displacing copper makes it harder for the copper ions to gain electrons from the iron, the neutralization and bringing the pH up (to around 9.5 to precipitate metals as hydroxides should be done after the copper is removed from solution.

Copper nitrate can used to generate some nitric acid, adding some more copper (like gold plated copper pins) (you could also add some sodium nitrate if wanted), adding sulfuric acid and distilling the mixture will dissolve the copper leaving gold flakes in a solution of copper sulfate (which can be reused in other processes like a copper cell) the gases from the distillation bubbled into cold water with a little hydrogen peroxide will give a nitric acid solution (see killing two birds with one stone. http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=38&t=6199


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## autumnwillow (Sep 19, 2015)

How long does it take to distill 1 gallon? Would that be economical?


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## butcher (Sep 19, 2015)

Killing two birds with one rock:
With the method I use to make nitric acid, collect gold foils from pins, make up a batch of copper sulfate for use in other processes or uses, (the method I call killing two birds with one stone), can be done in one afternoon, this will not provide a gallon of nitric acid, from a gallon of solution, I cannot remember how much nitric was produced but a quart or two of nitric acid (comes to mind from my bad memory).
Nitric acid to me is valuable, and can be hard to get and very expensive, to buy (or drive to the source paying for the gasoline to get it 250 miles from where I live), the recovered gold for me has value, the copper sulfate is also a commodity I use or do not have to buy...
The time spent was enjoyable, time spent in my hobby, giving me useful products for that hobby, and helping me to add some gold to my melting dish...

Note: For me this method was a way for me to make nitric acid, to recover gold from pins (dissolving the copper), and make a useful byproduct (copper sulfate for use in other processes), leaving me with no waste products to deal with, very economical in my mind...

I can also just make the nitric acid from the nitrate salt and sulfuric acid and distill that, either way the time spent distilling the nitric acid is about the same...

Distilling is a some what slow process as the gases condense in drops at a time, but before long those drops add up to enough of a product to give you a steady supply of reagent for use in the lab, well worth the time in my mind...


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## autumnwillow (Oct 14, 2015)

Well.. its been almost a month now, I don't think the copper is dropping. PH of the copper nitrate solution is 3.0. The iron (jeweller's files) that I dropped were covered with some black metallic crystals. There is a sign of copper but the quantity is very little compared to what I have dissolved in it. Probably about 10 gms of copper is present out of the 3 kgs that I have dissolved. What could have I done wrong? I tried to use a different type of iron (jeweller's old rolling mill handle) but it has the same result with the previous iron that I hanged, black crystals and very small amounts of copper. Take note that I am not using a bubbler, even if I did, the reaction is too slow for the bubbler to have even of any use.


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## Barren Realms 007 (Oct 14, 2015)

A bubbler helps with the process to keep the solution agitated and to help the copper release as it build up on the piece of iron being used. Filings are really not a good choice because they get coated too quick with the cementing copper unless there is constant stirring to keep the filling suspended in the solution. An iron sheet would work better than a round bar like a handle.


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## upcyclist (Oct 16, 2015)

Barren Realms 007 said:


> Filings are really not a good choice because they get coated too quick with the cementing copper unless there is constant stirring to keep the filling suspended in the solution. An iron sheet would work better than a round bar like a handle.



Just to clarify, he's using jeweler's_ files_, not filings. But since they're jeweler's files, they're still cylindrical and pretty small--especially if they're needle files. For scale: http://www.riogrande.com/Product/Jewelry-Apprentice-Tool-Kit/113963?Pos=6. The 11 files are in the lower-left corner, to the right of the 6 blue file handles.

--Eric


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## autumnwillow (Oct 30, 2015)

I used an iron rod this time. Seems to work better. I'm seeing copper crystals clinging to the rod, not the black ones like what I saw with the jeweler's files. I think it is better to use butcher's method for the treatment of this waste. I think it is more economical and good for the environment though a little more expensive for the fuel costs to distill the waste.

Question, if I distill this copper nitrate liquid and produce copper nitrate crystals, can I convert them to copper sulfate by simply adding sulfuric acid?


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## rickbb (Oct 30, 2015)

Files and other hardened tools are more steel than iron which is what was causing the slow results. The plain iron rod is doing better because it's iron, not steel.


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## butcher (Oct 30, 2015)

Question, if I distill this copper nitrate liquid and produce copper nitrate crystals, can I convert them to copper sulfate by simply adding sulfuric acid?

If you heated a copper nitrate solution (not distilling) you would drive off water from the solution to produce copper nitrate crystals.

Adding sulfuric acid to a solution of copper nitrate basically would not make a chemical reaction, you would just have copper ions, nitrate ions and sulfate ions all mixed in an acidic solution with the hydrogen of the acid.

We can drive off the more volatile liquids from a solution as gases, in the distillation process we can collect and condense these gases, some of these gases (like the NO nitric oxide gas) may need further treatment to make a byproduct (nitric acid) from them depending on the gas.

With the solution in discussion, copper nitrate solution with added sulfuric acid.
(adding some metal copper here would also help to drive the reaction, using gold plated copper pins would supply our copper and we could recover gold in the process).
Water is more volatile than nitric or its nitrate salt, so water will be the first to distill off the solution, as the solution concentrates, then the nitric or nitrates decompose to gases, NOx gas a mixture of nitrogen gases NO, NO2 et cetera.
NO2 gas is water soluble an the gas bubbled into water will make nitric acid.
NO gas is not water soluble, but in air converts to NO2 gas.
If we add some H2O2 to the water the oxygen in solution can convert NO to NO2, which with the water makes nitric acid.
Sulfuric acid or its sulfate are not very volatile, we really have to get the temperature up to a very high temperature before it breaks down and begins to distill off as gases, this is just great here, as we want to keep sulfuric in solution to make copper sulfate, as we distill of the NOx gases to make our nitric acid in the process.

NOX a combination of many different gases of nitrogen and oxygen
NO nitric oxide gas
NO2 nitrogen dioxide gas
H2O water
H2O2 hydrogen peroxide
O2 oxygen
HNO2 nitrous acid
HNO3 nitric acid
(g) gas
--> reaction (=)

some chemical reactions of the gases we are discussing distilling to make the nitric acid.
NO (g) + O2 (g) --> NO2 (g)
3 NO2 + H2O --> 2HNO3 + NO
2 NO2 + H2O → HNO2 + HNO3
HNO2 + H2O2 --> HNO3 + H2O
4 NO + 3 O2 + 2 H2O → 4 HNO3
4 NO2 + 2 H2O + O2 → 4 HNO3

Distilling off the water and the nitrates as gases (to form our nitric acid in the distillation process) from the solution we are left with copper ions and sulfate ions in solution making a solution of copper sulfate.

Read some of the links provided earlier, you may get a better understanding, also there are also a lot of post I have made on nitric acid and its reactions and ways it can be made, searching certain keywords with an author can be helpful, also many members here on the forum have made many different post on nitric and its oxides and reactions or how to make nitric acid...


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## patnor1011 (Oct 30, 2015)

I do use CD ROM casing for dropping copper out of waste solution. CD/DVD floppy it does not matter, work for me every time.


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