# hydroflouric acid and silica



## kjavanb123 (Apr 18, 2009)

ok, I have this ore containing 63% Sio2. I learned from wiki that chemical reaction is as following.

Sio2 + 4HF ----> SiF4 + 2H2o
Sio2 + 6HF ----> H(SiF4) + 2H2o

Now all the chemist here, what does above means in grams of silica and grams or litre of hydroflouric acid mixture? does this means 1 part silica must be added to 4 parts of HF to be completely resolved?

Thanks


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## markqf1 (Apr 18, 2009)

Thats gonna be a mighty expensive way to get rid of sand.

The cost of the acid is high and then, you'll have to contend with waste disposal.

Also, HF is real nasty stuff to the human body.

Look real hard before you leap.

Have you considered a furnace?

Mark


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## goldsilverpro (Apr 18, 2009)

This is a duplicate of the post I made on another thread you started concerning HF.

I certainly wouldn't want to use HF in that quantity. If you haven't used HF before, you don't know what you're getting into. A little on your skin can burn to the bone - very painfully - I've been there. Of all the common inorganic chemicals, it is by far the most dangerous to use, in my estimation. It frightens me when discussion of the use of HF is tossed around so lightly on this forum. Were it up to me, discussion of its use would not be allowed on this forum.


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## kjavanb123 (Apr 18, 2009)

Indeed using HF ( hydroflouric acid ) is not feasible. But this is how most invention take place in human lives. Just trial and error.


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## jsargent (Apr 18, 2009)

goldsilverpro said:


> This is a duplicate of the post I made on another thread you started concerning HF.
> 
> I certainly wouldn't want to use HF in that quantity. If you haven't used HF before, you don't know what you're getting into. A little on your skin can burn to the bone - very painfully - I've been there. Of all the common inorganic chemicals, it is by far the most dangerous to use, in my estimation. It frightens me when discussion of the use of HF is tossed around so lightly on this forum. Were it up to me, discussion of its use would not be allowed on this forum.



Indeed. I buy some of my chemicals at a HUGE chemical supply house and they sell every chemical known to man. In the lobby, where you wait while they load your truck, there is one, very large, poster listing the multiple hazards and effects of, you guessed it, hydrofluoric acid. Nobody in there right mind wants to handle the stuff if they can avoid it.


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## Harold_V (Apr 20, 2009)

I have a liter of HFl, which I use to kill warts. A single drop applied by a toothpick is almost instantly absorbed into the skin. A few days and the wart will shed. I would suggest everyone avoid the use of HFl if at all possible. It's wicked stuff. 

As far as silica is concerned, it is easily dissolved with soda ash in the furnace, at which time it can be poured off as slag. I relied on that very process for recovering my waste materials from years of refining. 

A collector would likely be required. 

Harold


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## kjavanb123 (Apr 20, 2009)

Harold,

Please advise adding soda ash to silica and heat in furnace would change the melting temp? Because before we used to just melt the soil with heavy metals, and silica. then add some lead sulfide in process to remove the melted silica which stayed at the top, and bottom would represent all the heavy metals.

Now I hope adding soda ash would decrease the melting temp, as silica melts at 750 celsious, is that true? 

Thanks


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## kjavanb123 (Apr 20, 2009)

Also soda ash ( Sodium Carobante ) cost around $25 per kg. that doesn't seem like a good commercial use when we are planning to process 20tons of tailing dump per day. 

I think cyanide or thiosulfate leaching would be the best thing to go. Any info on consulting companies that can design this system?


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## Harold_V (Apr 20, 2009)

kjavanb123 said:


> Harold,
> 
> Please advise adding soda ash to silica and heat in furnace would change the melting temp? Because before we used to just melt the soil with heavy metals, and silica. then add some lead sulfide in process to remove the melted silica which stayed at the top, and bottom would represent all the heavy metals.
> 
> ...



I'm not a chemist, so I may say something that's not exactly correct, so please bear with me. 

To my knowledge, silica melts @ 1405 C. When it is heated in the presence of soda ash, the soda ash dissolves the silica, resulting in common glass, which will melt at a much lower temperature. I do not know the exact temperature, which is likely a function of the ratio of silica to soda ash, perhaps with other constituents modifying the results. 

I read your comment on the price of soda ash, and would suggest that it would be very expensive, although I am sure that if you bought it in large quantities the price would come down appreciably. 

I think the point here is that if you do not have alternate methods to recover the values, and are forced to recover them by furnace, that would be an example of ways to proceed. In my case, cost was not an issue in that the 500 pounds of soda ash I had to buy resulted in the recovery of over 200 troy ounces of gold, more than that amount of silver, along with a substantial amount of platinum and palladium. 
Processing a low grade ore would likely be a different matter. 

Sorry I'm not more help. This subject is way over my head. I don't know of companies that suggest processes, so I'm no help there, either. 

Harold


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## arthur kierski (Apr 20, 2009)

Harold,what colector should be used in your soda ash process to dissololve the silica? could this be used in cat substrates?thanks for your reply
Arthur


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## goldsilverpro (Apr 20, 2009)

Arm & Hammer "Super Washing Soda" is 100% soda ash and, the last I looked, cost about $1/pound.


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## leavemealone (Apr 20, 2009)

KJ I don't know if you have been deterred yet from using HF but let me shed some light on something.My neighboor is an EMT ,and he said that in the medical field,HF acid is nicknamed "The Bone Robber".When the fumes or vapors are inhaled,even in extremely low quantities,it will dissolve and destroy calcium.Months later it can still be in your bloodstream,and there is no way to get it out.It will eventually destroy your bones,and teeth.On the exterior,it is as bad as lye.......on steroids.I am not saying this to glorify HF,I am doing this in hopes of scaring you into not using it at all.I understand your trial and error theory,but you need to remember that MANY MANY others have used HF and can show you the "error" of their ways.Here is an example of my point,harold says he uses it to remove warts right?Well warts are one of the hardest things in the world to get rid of.Think about this,people go have surgery to have them removed,and there are several products over the counter that "freeze" them,or "burn" them.Harold puts "a single drop" on one and it falls off.So please put this idea away bud.No disrespect.
Johnny


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## markqf1 (Apr 20, 2009)

It's gonna take a huge furnace to run tonnage, which is what you'll have to do to make money from an ore with such a small percentage of pm's.

I'm not trying to be negative, but this is what can make some ores cost prohibitive.

From what I read, cyanide is usually the cheapest way to go for this type ore.

A new set of problems. :? 

Mark


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## kjavanb123 (Apr 20, 2009)

Thanks all for your warning about using of HF, and indeed after some calculation the costs of using HF in ore processing is way more than amount of PMs in ore. I am studying all the bits and pieces about using cyanide soultion.

This guy has put some interesting testing page about using cyanide solution here, please advise if this is reliable.

here is the link.
http://66.113.204.26/mining/minproc/cyanide-leach-test.htm


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## Lou (Apr 20, 2009)

Soda ash is dirt cheap...cents on the pound in bulk.


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## ck (Apr 20, 2009)

deleted


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## markqf1 (Apr 20, 2009)

That site seems to provide a pretty good oversight , compared to what I have read.
Have you run the numbers that they suggested, on your ore?

One thing I have learned about using cyanide is, it is not that toxic to use in small increments.

A TV show I was watching the other day said that, you would have to drink a quart of the solution that they were using, just to make you sick.

Also, it supposedly dissapates itself over a short period of time.
I'm not by any means saying it's safe!


Testing , testing, testing = $ saved.

Mark


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## Harold_V (Apr 21, 2009)

arthur kierski said:


> Harold,what colector should be used in your soda ash process to dissololve the silica? could this be used in cat substrates?thanks for your reply
> Arthur


In my case, Arthur, my waste material consisted of a fair amount of silver chloride, along with cemented copper from my stock pot. It also contained traces of gold, which was entrapped in the silver chloride, plus platinum group values that had been intentionally placed in the stock pot from aqua regia solutions from which gold had been recovered. In most cases, the concentration was too low for recovery by conventional methods. As it turns out, at least for my purpose, the decisions I made turned out to be to advantage. There was enough silver chloride and copper present to perform as a collector. 

My slag was assayed, only to find it was so low in value that it was not worth re-processing for values, using litharge. I felt I had accomplished the task well, considering I had no experience in the art of reducing elements in the furnace. It did require a considerable amount of research, which included the discovery that adding fluorspar to flux thins it exceedingly well. Because of the use of fluorspar, I found no prills in any of the slag, all of which was closely examined. 

As for you processing cat substrates, I am of the opinion that you would not enjoy the same degree of success, but I also do not know the chemical composition of the substrate of which you speak. If it is a refractory material, I have my serious doubts as to the affectivity of the flux recipe I used. I will gladly share it with you if you would like. I have posted it before. 

Hope this helps. 

Harold


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## Harold_V (Apr 21, 2009)

ck said:


> Harold_V:
> 
> MethAcrylic acid is better for warts, pick up a bottle of nailprimer.


Thanks for the tip! I do not prefer to use the HFl, but failing to have anything else with a similar behavior, I tried it on my wife's plantar wart. Worked wonders!

The only other use I ever had for the stuff, which came to me from a lab I cleaned out, was to pickle melted platinum. I did that in my fume hood, using a platinum crucible. It removed traces of the melted dish very nicely without defacing the buttons. It's nothing short of amazing how long a liter of HFl acid can last when it's used sparingly! 

Harold


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## Harold_V (Apr 21, 2009)

markqf1 said:


> One thing I have learned about using cyanide is, it is not that toxic to use in small increments.
> 
> A TV show I was watching the other day said that, you would have to drink a quart of the solution that they were using, just to make you sick.


I'd believe that only after witnessing a person responsible for making the claim, drink a glass full. Even then I'd have my doubts. 

Cyanide when used for leaching gold and silver is used in very dilute concentrations, so it remains selective. We have discussed this in the past couple weeks, as I recall. 

I recall that I had to keep my concentration level around .02% maximum, to avoid killing the bromine that was required for the extraction process I used. I wouldn't wish to drink even a drop of that solution, secure in the knowledge that it would likely kill me. Cyanide kills by binding red blood cells such that they can not carry oxygen. I have no idea how much it takes, but I believe it to be very little. According to the Merck Index, a lethal dosage in rats, orally, is 15 mg/kg. 

Be cautions about using cyanide----don't believe any of the tales you may hear about how harmless it may be. It should be well respected. 

Harold


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## kjavanb123 (Apr 21, 2009)

only 0.02% NaCN in cyanide solution? I read for bottle roll cyanide soultion testing to get the 0.5% concentrate NaCN solution, 300mL water is added to 16g of NaCN. How much cyanide is needed to process a ton of grind gold ore? Is you are saying the 0.02% cyanide is the maximum then it seems very economical to use cyanide leaching to process gold ore.

Thanks


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## Harold_V (Apr 21, 2009)

A very small amount of cyanide in solution (low percentage) is recommended, to avoid dissolving copper. A ton of gold ore can be processed with a pound of cyanide (or even an ounce), for the only loss, assuming there are no cyanicides, is what is consumed dissolving silver and gold, at least in theory. 

Everything depends on the nature of the material----which must not be a sulfide. If the tailings you speak of are 40 years old, they may well be oxidized, but I am not knowledgably in such things. It might be in your best interest to have the material analyzed so you have a perfect understanding of its nature. 

Remember, the material must not have the ability to change the pH of your cyanide solution. If it reaches a pH of 9.5, you border on liberating hydrocyanic acid, deadly fumes. It is desirable to keep the pH above 11. 

Harold


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## kjavanb123 (Apr 27, 2009)

I guess the best soultion to use the tailing pile that contains 63% Sio2 would be to produce Soda-lime glass. I still believe there must be some gold and silver in it. plus it's a big quantity (5million tons) then even at 0.5ppm Au and 10ppm Ag would make this a prophry type. Since it's already crushed and fined and extracted.


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## arthur kierski (Apr 27, 2009)

thanks harold for your answer and explanation about the collector--you used as a colector silver chloride +copper from your waste (stock pot) --it was in your particular context and not a usual procedure -


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