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Author: Subject: Arsenic disposal
Rainwater
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[*] posted on 24-3-2022 at 18:26
Arsenic disposal


Got a new batch of ore processed and had some very weird things happening.
I finally nailed down my contaminate with an arsenic test from the hardware store

Now im left with a few liters of solution containing about 10~20 grams of As
Little worried about trying to reduce the solution by boiling the water off.

A quick search on wiki and im thinking the safest form will be Arsenic sulfide as its insoluble in water.
Any advice would be appreciated.

The extraction procedure was as follows.
Quartz ore crushed to 50 mesh, then wet sorted.
10 kg of Consentrates recovered were soaked in boiling 40% NaOH solution
The solution was filtered, and a strong yellow sand was collected along with the normal stuff.

During my refining, I also noticed unusual colors coming into my solution and then disappearing with heat. The concentrates turned dark blue when I added nitric acid to the solution to pull out the base metals. Upon heating, I observed much more NO2 gas coming off than what usually occurs.
Cementing of silver worked normal, aqua regia treatment went as expected.
Once filtered i added h2so4, i got a dark yellow percipitate. Lead usually percipitates as a dark gray.




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Texium
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[*] posted on 24-3-2022 at 18:48


Considering you treated the sample with nitric acid and aqua regia, the arsenic in your solution should be present as arsenic acid (as in, the acid form of arsenate(V)). According to Wikipedia, “Arsenic acid is prepared by treating arsenic trioxide with concentrated nitric acid. Dinitrogen trioxide is produced as a by-product.” The N2O3 byproduct could be an explanation of the intense blue color that you saw, if that color was fleeting. It decomposes pretty rapidly at room temp or warmer to NO and NO2.

Arsenate is analogous to phosphate, and most things that will precipitate phosphate should precipitate arsenate. Lead arsenate is highly insoluble, so if you were to add some lead nitrate, it should precipitate as a white solid. You could filter that out and then precipitate the excess lead by your usual method.

Edit: as for the dark yellow precipitate when you added sulfuric acid, I’ve got no idea. That doesn’t sound like it has to do with arsenic.

[Edited on 3-25-2022 by Texium]




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[*] posted on 25-3-2022 at 09:55


Lead arsenate looks to have a melting point of 1042c.
But, another search shows a decomposition temp of 280c, with arsenic and lead gases produced.

I guess I'll just seal it inside a glass tube until i can figure out the safest way to be rid of it.
It would be nice if it could be safely turned into borax glass for disposal in a land fill.




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[*] posted on 26-3-2022 at 00:57


lead oxide is a good flux for glass.
arsenic trioxide, not so much, it boils.

According hazardous laboratory chemicals disposal guide by Armour arsenic should be converted to the sulfide for disposal.

Inclusion of the sulfide in cement supposedly renders it safe for disposal in a landfill.


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[*] posted on 26-3-2022 at 04:48


Copper(II) aresenate is very, very insoluble at neutral or high pH, and would make a pretty nice trophy to keep (very pretty blue-green color) if you're confident you can store it safely. Personally I don't have any plans at all to conduct arsenic chemistry in the future because of the dangers of both acute and chronic exposure. But since you're already here I really recommend getting your blood checked for arsenic poisoning after this is all said and done. The procedures and quantities you conducted them in sound like a great way to get tiny particles everywhere.
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[*] posted on 26-3-2022 at 07:07


Quote: Originally posted by Amos  
. But since you're already here I really recommend getting your blood checked for arsenic poisoning after this is all said and done. The procedures and quantities you conducted them in sound like a great way to get tiny particles everywhere.


It's not a bad piece of advice.

The only exposure I've had was the first crush and loading the ballmill. I keep dust to the minimum best I can. But, respiratory precautions are a must for me. After that, everything is dust free. The material is kept wet during grinding to avoid losing the gold. And to make the process more efficient.

Then, after being panned out, I guess I'm exposed again through the water

So ya. Im calling my dr to setup an appointment just in case.
Note to self. Were your gloves, always. Even if its just sand.




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[*] posted on 26-3-2022 at 21:08


Just because I'm presently looking at barium,
barium arsenate solubility 2.6x10-9




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