Processing Galena and other lead-zinc based sulfide ores

[Mad Machinist]

I'm gonna start this off with saying whoever voted to close the Bureau of Mines needs some very bad things done to them where the sun don't shine.

In order to do this, one is going to have to play with a few rather nasty substances, but if the proper precautions are taken this is no different from aqua regia.

In going through amd organizing almost 25 years of notes in preparation to start mining a deposit, I found a publication put out by the now defunct Bureau of Mines. And while messing with a few pretty nasty things is necessary, a while lot of problems are solved environmentally


Flourosilicic acid, a byproduct if the fertilizer industry, will selectively dissolve lead, zinc, and the sulfur side of sulfide based ores.The other metals such as copper, silver gold, platinum metals, and rare earth metals with drop to the bottom of the tank as a "sludge" to be dealt with through other processes.

Now before anyone jumps on this screaming the grail has been found, flourosilicic acid contains a small amount of hydrofluoric acid as an impurity. Hydrofluoric acid will mess you up really bad if the proper precautions are not taken. Respiratory and body protection are required.

The lead can be recovered as a 99.94% purity with a simple electrowinning cell. Lead still has uses that are not going to disappear any time soon.

The zinc can be recovered in a closed circuit system by bubbling hydrogen sulfide through the spent electrolyte. Another nasty substance that needs.respect and proper precautions. The zinc will precipitate as zinc sulfide solid that can be recovered and sold.

The sulfide side of the ore can be recovered by a simple solvent extraction system. It will come out as elemental sulfur that is easily stored, transported, and sold for various reasons.

Flourosilicic acid spills are neutralized by the addition of lime and dilution with water. Like I said, if the proper precautions are taken it's no more dangerous than driving to your local Walmart.

Lead, zinc, amd sulfur emissions are pretty much eliminated with this.

 

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[Mad Machinist]

https://www.google.com/search?clien...11.0j17......0....1.........30i10.QRfk2MTB4Yc

About halfway down the page you'll find the pdf. It's called Hydrometallurgical Process for producing lead amd elemental sulfur.

Some other interesting stuff there too.

 

[Mad Machinist]

Double post. My phone is being stupid again.

 

[Mad Machinist]

Ok, here's a little more on the process since I studied m
the flow sheet, the text, and the process. This is setup for a 1 ton per day thing so your gonna have to do some math to scale it up or down.

1 ton of Galena occupies 2.82 cubic feet. So if you put a like amount of the fluosilicic acid in you'll be a 5.64 feet. 5.64 cubic feet times 7.48 gallons per cubic foot equals a 42.187 gallon container. Since an excess of reagent is better, figure on at least a 55 gallon size container. 100 gallon would be better.

So the flousilicic acid will selectively dissolve lead and zinc. Once this is done, the leachette is drained off, filtered, and sent straight to an electrowinning cell to recover the lead as cathode plate. Once the fluo acid is taken to a lean condition, this passed through a bed of activated carbon to remove minor impurities, then recycled back into the process. An Interesting side note here is lead is still used in many SX/EW tankhouses to recover other metals such as copper so it still has uses.

Anyhow, once the resultant "sludge" is dried, it is exposed to a mixture of tetrachloroethylene and kerosene heated to a temp of 110 to 115 degrees C (230 to 239 degrees F for you non metric people) to dissolve the sulfur as sulfides in the "sludge". Once the tetrachloroethylene/kerosene mixture cools to room temp, the sulfur with crystalize out as elemental sulfur on it's own. The tetra/kero mixture is then recycled for the next run.

Once these two things are done, the "sludge" that is left over has basically been converted to oxides and can be directly smelted or put through whatever process suits your fancy to recover the base and precious metals that are left.

Yes, there are "less toxic" ways to do this, but the reagents used are normally consumed in the process. This leads to higher costs. In order to do this "cheaply, effectively, and economically" you either learn to respect what you are working with and take the proper precautions or you don't do this at all.