Halide extraction: cloudy vs. clear liquor

[scwiers]

Just a report: I treated two buckets of ore, side by side. Both were pre-treated w/ HCl until there was no more reaction, and then poured off, and rinsed with tap water.

Then, one got treated with HCl and bleach oxidizer, only, over a period of two days. The result was a cloudy liquor that proved difficult to filter.

The other bucket got treated with a nearly-saturated brine solution, plus the same amount of HCl and bleach oxidizer, over two days. A much clearer, dark emerald solution, easier to filter.

I'm hoping that this confirms that NaCl in solution actually helps dissolve the PM values.

 

[eagle2]

Yes, I use salt in my leach and PM dissolving solutions. It does make a better mix.

But not too many other members here use it. What kind of ore are you processing? Does it have some Copper in it, to get that emerald color?

Al

 

[scwiers]

hi Eagle, by 'ore' I mean the fine powder that I get after crushing electronics components through a ball mill, and then basically, leaching it in buckets. Probably just about every common metal is in there.

My sense of reading something, somewhere, is that having an NaCl solution makes the Cl- ions produced in the HCl/clorox more likely to attack the metals, and keep them in solution longer (= transparent dark emerald solution); whereas just the HCl/clorox doesn't leave the Cl- anything to 'bounce' off to attack the metals. Even when it does form a chloride, it's like it's barely hanging on (= cloudy/milky solution). I'm wondering, as an alternative explanation, whether or not the NaCl in solution cuts down on the Pb, Ag, and Hg chlorides going into solution.

Of course, in my bass-ackwards way, I'm just doing heap-leaching, and having to deal with practically every metalic chloride substance there is.

Order of operations, basically: crush - sieve - HCl treatment to remove base metals - H20 rinse - NaCl/HCl/clorox leach - first precipitation with Zn or Al, as available, and from here on, parting with HN, and running AR as described in the Hoke book, and elsewhere at this site.

 

[OMG]

I read once in a google book that a chloride salt + HCl makes the HCl work a lot better. I see you are using NaCl. They suggested that using the calcium or magnesium chloride salt works much better than NaCl.
It is in the google book
Hydrometallurgy in Extraction Processes
on page 15
says a 2M HCl with 3M CaCl2 solution has the equivalent strength of a 7M HCl solution.
I'm not that chemically inclined but you may want to try that out.

 

[Shecker]

I regularly use NaCl as a component of an HCl-Cl leach on real mineralogical ores. It helps to drive the formation of chlorine and the sodium will help to break up naturally occurring organometallic compounds that exist in nature. In the case of e-scrap the sodium might help break down certain carbon based components of boards but the extra chlorine would increase the production of lead chloride, silver chloride, and potentially copper chloride. The CuCl would be soluble while PbCl and AgCl would form insoluble complexes. These would become part of the filtered residue and would require seperate treatment for silver recovery. Just a thought here -- once the left over residue has been well washed the AgCl can be removed selectively by sodium thiosulfate and recovered by means given elsewhere on this forum.

Randy in Gunnison

 

[eagle2]

Hi, Yes, I had a previous post that gave some of the chemistry with using salt in a copper leach. basically the more salt you used the less HCl you needed to make up the starting leach solution. During the leaching of the scrap the HCl is used up, but the salt is not used up, yet it does enter into the chemical reactions going on.

You do need to add more HCl from time to time to keep the solution acid. Probably below PH 1 is best. Also adding H2O2 or keep a bubbler going.

OMG`s note about CaCl is great. I thought there could be better Salts than just NaCl.

Shecker, I have used Ammonia on those types of residues to extract the Silver.

I also use Zinc dust to clean out PM`s from heavily loaded leach solutions.

Al

 

[scwiers]

thanx Eagle and Schecker, from now on, I'll be sure to rinse out Ag values w/ Ammonia. Up until now, I'd just been turning the spent ore into concrete blocks. Concrete blocks high in silver chloride values...

 

[eagle2]

Be careful, with the use of Ammonia.

It will dissolve out the Silver, Lead and Copper Chlorides. Then a slightly acid (HCl) PH will precip Silver Chloride from the Copper ion. Copper wil stay in solution. Lead will precip with the Silver, but can be removed with hot water rinses.

Ammonia can form explosive compounds with Silver. Just a simple prevention is not to let dissolved Silver dry out while in Ammonia. Precip it immediately with HCl.

Al