# Jeweler's Waste Floor Mat and Wipes Part 2 - VIDEO



## kadriver (Mar 20, 2016)

This was a struggle for me. I tied up my facility and time for almost two weeks to get this completed.

I got some strange reactions from this waste. I am still baffled by how some of them turned out.

It was a new venture and I know I made some mistakes, but I learned a few things as well.

Any comments or critique would be welcomed.

https://youtu.be/_eETvvd_AOk

Thank you,
kadriver


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## Smack (Mar 20, 2016)

Maybe lead (Pb) was the problem. I didn't see you add sulfuric to test for or drop any Pb after your last digestion in A/R either or maybe you didn't film that part.


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## nickvc (Mar 20, 2016)

Over the years I have runs hundreds perhaps thousands of sweeps and they are troublesome on many occasions but I'll give you a rundown of my processing.
The incineration was always a two part process, first the sweeps were covered with Ali's and heated, the lid needs some vents to allow the smoke to escape slowly as if it burns too fast it will carry values away, once the smoking had stopped I'd remove the cover and incinerate again stirring carefully to ensure full incineration. The next step was crushing and sieving the recovered waste and removing any magnetics from them, these were kept as values frequently came with them especially Pt, a soak in hot HCl usually revealed any trapped values which were put with the rest for recovery, the rest of the magnetics went in my stock pot. Unless I knew or suspected silver I never bothered trying to recover it but went straight for a good covering of HCl which was heated to boiling, stirring is essential in this to avoid hot spots and then small additions of nitric again stirring to mix once the initial reaction slows, keeping the beaker covered when not stirring, once I got no more reaction I'd allow it to cool remove as much of the pregnant solution as possible for filtering first and then filter the solids also with good rinsing and stirring with a good vacuum to extract as much of the values as possible. 
The one thing I did learn is that using this process you will only recover around 90% of the values if you do it correctly much less if you don't , the essential part is to keep the solution gently boiling, one of the few times you want that to occur as it helps agitate the powder allowing the AR to reach more of the values, Harold used a HCl soak and then filtered to start which makes sense as it removes many base metals and sweeps can and do contain lots of trash.
I feel for you as sweeps can be a nightmare for the little values they contain, I ran them along side other materials but always charged a lot more for the refining due to the time and effort they require to do correctly.


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## g_axelsson (Mar 20, 2016)

Interesting video, you surely had to work hard for that gold. 8) 

I see it unlikely that there should be a lot of lead in a mat from a gold shop.

Just a thought...

There is another element that could create some problems, calcium. It might be used as a filler in paper in the form of calcium carbonate, and possibly also in the mat.
With sulfuric acid it forms a precipitate of calcium sulfate, also called anhydrite.

SMB reacting with acid gives sulfuric acid as a byproduct so if calcium is present it would also precipitate a white solid with the gold.

Edit : The above statement is just wrong, as I was pointed out in a PM. Thanks Barren!
SMB + hydrochloric acid creates sodium chloride and SO2.

Doing some more research I discovered that calcium sulfite have a very low solubility too, (43 mg/l H2O @ 18C). To me it suggests that SMB + calcium would precipitate a white solid.
Calcium sulfite is also oxidized by oxygen into calcium sulfate.

The step where kadriver adds sulfuric acid and creates even more white crystals also speaks for a insoluble sulfite / sulfate being the culprit. 
http://www.chem.sc.edu/faculty/morgan/resources/solubility/


http://www.chem.sc.edu/faculty/morgan/resources/solubility/ said:


> Rule 5. All sulfate ( SO4=) compounds are soluble except those of Ba2+, Sr2+, Ca2+, Pb2+, Hg22+, and Hg2+, Ca2+ and Ag+ sulfates are only moderately soluble.



So out of Ba, Sr, Ca, Pb and Hg we would only expect Ca and Pb in any larger amount, and I don't think Pb would show up in such a large amount either, making calcium my prime suspect.

https://en.wikipedia.org/wiki/Calcium_sulfite


Calcium is easily removed with hydrochloric or nitric acid as long as it hasn't reacted with sulfuric acid. It might have been a mistake to not filter off the nitric before adding hydrochloric acid and creating AR.

Göran


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## g_axelsson (Mar 20, 2016)

I was pointed out that my above statement contained a grave error so I have added a correction to it.

Göran


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## kadriver (Mar 21, 2016)

Thank you for those responses. I was at a loss here. This stuff kicked my behind.

Smack, I was so glad to be nearing the end of this that I skipped the H2SO4, just plain forgot it.

I'm glad you pointed that out, I'll dissolve the button again and add some sulfuric before I turn it over to the jeweler. I'm glad you caught that.This thing just keeps coming back in my face! 

Goran and Nick, your responses are loaded with insight. I'm printing them and I'll study it more. Did you notice that I got the best result with hot HCl? That would seem to fit with the calcium diagnosis.

And something I forgot, these guys use boric acid for something in their processes, but I'm not sure what it is.

This was a fantastic experience, and I learned some new lessons.

I know that there is still some residual gold in those solids. 90% yield is not what I was thinking, but it's a little bit of peace of mind for me to hear that.

I never want to see another big bag of paper towel wipes - 

Thanks again you guys.

kadriver


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## maynman1751 (Mar 21, 2016)

Question Kevin! Why did you feel it necessary to inquart the nearly pure gold before re-refining it? It should have been pure enough to go straight to AR. Just asking!!!!???? :?:


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## kurtak (Mar 21, 2016)

nickvc said:


> first the sweeps were covered with Ali's and heated, .



Nick - I assume you meant to type *a lid* (per the underlined above)



> The incineration was always a two part process, first the sweeps were covered with Ali's and heated, the lid needs some vents to allow the smoke to escape slowly as if it burns too fast it will carry values away, once the smoking had stopped I'd remove the cover and incinerate again stirring carefully to ensure full incineration.



Nick is correct - if the wipes contain metal salts from wiping up solutions they first need to undergo a reduction roast (think calcine) to reduce the salt to metal --- about 600 degrees F no oxygen (hence the lid) & then an oxidation roast (complete incineration)



> Harold used a HCl soak and then filtered to start which makes sense as it removes many base metals and sweeps can and do contain lots of trash.



correct again --- you want to do a HCl leach first to remove any HCl soluble metals &/or oxides - filter/wash - dry & then roast again to drive of any "trace" HCl - then you can do a nitric treatment to rid Cu, Ag, etc. - filter/wash *good* - then AR 

Kurt


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## kadriver (Mar 21, 2016)

maynman1751 said:


> Question Kevin! Why did you feel it necessary to inquart the nearly pure gold before re-refining it? It should have been pure enough to go straight to AR. Just asking!!!!???? :?:




The buttons weighed 11 grams. After inquarting and refining with Aqua Regia I got 10.2 grams of pure gold.

This tells me that there was some other metals, possibly silver, in with the gold buttons.

The melt dishes I used were dirty with copper and silver. I knew there would be some of these metals in with the gold buttons. I've learned from experience that inquarting and parting with nitric will work wonders - _this is why I chose to inquart and part with nitric instead of going straight to AR._

Probably could have just went straight to AR and been just fine. But did you see how cleanly the gold dissolved in the AR after the silver had been removed with nitric? The resulting chloroauric acid solution was clear and bright orange in color.

I love to look at the color and beauty of a clean and crystal clear chloroauric acid solution!

kadriver


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## UncleBenBen (Mar 21, 2016)

kadriver said:


> I love to look at the color and beauty of a clean and crystal clear chloroauric acid solution!



No real arguing that point! About the same reason I've melted my first little bit a half dozen times. That glow of liquid gold...
Like my dear grandmother used to say, "oh my!"


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## maynman1751 (Mar 22, 2016)

kadriver said:


> maynman1751 said:
> 
> 
> > Question Kevin! Why did you feel it necessary to inquart the nearly pure gold before re-refining it? It should have been pure enough to go straight to AR. Just asking!!!!???? :?:
> ...



Thanks Kevin! Just wondered and now I understand. 8)


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## goldenchild (Mar 22, 2016)

Man what a nightmare that turned out to be! It seemed like something went wrong at every turn. I've had my fair share of those runs and you end up wanting nothing more than for it to just be over. So I gotta ask... Would you ever want to do sweeps like this again in great quantity?


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## nickvc (Mar 22, 2016)

If you process sweeps correctly and charge fairly you can get quite a lot of them, we used to get lots of them, they can be a pain but most refiners rip off the customers on sweeps working on the assumption they couldn't possibly know what they contain, we had one customer who weighed everything at each process to gain some insight but unfortunately he didn't allow for gold particles that went every where including down his drain, out of the window and through his door, it took me a long time to get him to see where his loses were occurring and they were not in my pocket! We always quoted 2 weeks at least for sweeps, some were done in days others in 3 weeks depending on volume and contents, the things I found in sweeps were really unbelievable at times :shock: 
In honesty 25-35% is a fair charge they take time, chemicals and expertise, the best sweeps we got were from polishing or lapping after that from setters or melting rooms.
When I worked for JM we had one large customer who sent sweeps twice a year, very large volumes, they had earrings in plastic cases, sandwiches, mandrels you name it it was in there, staff just do not care, the melt from the solids were frequently 3-5 kilos of gold, plus the powders !


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## upcyclist (Mar 22, 2016)

kadriver said:


> And something I forgot, these guys use boric acid for something in their processes, but I'm not sure what it is.


A dip of boric acid in alcohol is used for firecoating, i.e., preventing firescale (copper oxide) during soldering. Apparently it has to do with the difference in the way borax flux and boric acid decompose into boric trioxide. When boric acid decomposes, the copper metaborates formed by reaction of the boron trioxide & copper oxide cling to the surface, preventing further oxidization of the copper. The copper metaborates (same as those formed by flux) are soluble in pickle.


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## 4metals (Mar 22, 2016)

> If you process sweeps correctly and charge fairly you can get quite a lot of them



There are sweeps and then there is this stuff. Floor tiles, floor mats, and carpeting are technically sweeps *but they are difficult to say the least. * As we have said on this forum before, all sweeps processed in Aqua regia retain some gold. It is due to the filtration and rinsing process. It is just a bear to rinse well. This stuff has less gold to start with than most jewelers sweeps and it inherently filters poorly so your recovery will suffer. 

I know a lot of refiners who do sweeps in acid these days. When they do them, the residues always assay around 1/4% (one quarter of one percent) Plus all of the silver is in the residues as well. So they have to prepare these sweeps and send them out when they get 1 or 2 drums. They all take in carpets and floor tiles and mats as well but once they get it into assayable form, they sample it and put it in their drum of low grade to ship out. It rarely yields high, especially the powder, (and the metallic fraction sifted off can be melted and refined easily) so they just assay the powder and ship it with the refining residues. And the only reason they bother is to keep a customer happy so he doesn't go looking for another refiner.


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