Processing nitric waste before disposal

[autumnwillow]

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?

 

[kurtak]

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

 

[MarcoP]

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.

 

[autumnwillow]

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

 

[kurtak]

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

 

[kurtak]

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

 

[4metals]

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.

 

[autumnwillow]

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.

 

[4metals]

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.

 

[goldsilverpro]

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.

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

 

[4metals]

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.

 

[solar_plasma]

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?

 

[4metals]

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.

 

[Lou]

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.

 

[autumnwillow]

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

 

[FrugalRefiner]

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

Dave

 

[autumnwillow]

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

 

[kadriver]

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

 

[autumnwillow]

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?

 

[autumnwillow]

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.