Sciencemadness Discussion Board

Granite hydrolisis?

angeltxilon - 7-10-2017 at 05:40

Ir amor trying to separate granite components. One way imperfect is to decompose it, produce kaolite from feldspar and iron oxydes from moscovite.

I wonder if it is possible to hydrolize artificially and fastly the feldspar, or what I could do for degradate and separate granite components.

barbs09 - 7-10-2017 at 06:10

Hello, I have spent many weeks isolating the components of granite for the purposes of separating zircons for radiometric dating. First question: why? What are you hoping to isolate? Any conditions capable of weathering feldspar will also weather hornblende etc, though perhaps not on a time scale you will be pleased with. You will be left with kaolinite, quartz some muscovite and accessory minerals (including zircon).

Perhaps a strong alkali solution?

The standard methodology to separate accessory minerals including zircon from granite is to mechanically break it down to a sand grain size in a ring mill, and use successive heavy liquids to isolate the mineral you are after. Luckily for radiometric dating, zircon, the target mineral, is dense and easily separated from the less dense minerals.

crystal grower - 7-10-2017 at 07:10

As has been said already, it really depends on your goal.
Btw, HF might be used to get rid of the SiO2.

barbs09 - 8-10-2017 at 04:36

HF sure will!!!!!!

angeltxilon - 8-10-2017 at 12:55

I want avoid to use HF, this is a dangerous compound that doesn't entries in my current chemistry experience and domain.

I was wondering if there are more mechanical processes like the use of dense liquids.

j_sum1 - 8-10-2017 at 17:01

Cody (cody's lab)recently did a video on flotation separation with dense liquids. Since this is an actual industrial process there is bound to be some research to be done. The problem as I see it with employing this method on granite is that it necessarily requires crushing your material to particles that are mostly one mineral. At this scale you cannot guarantee that the particles will separate via the liquid. Surface properties come into play and the forces associated with surface tension will be greater than the buoyancy and gravitational forces experienced.

Drop the dense liquid and use a form of panning to separate.

SWIM - 8-10-2017 at 17:18

Quote: Originally posted by barbs09  
Hello, I have spent many weeks isolating the components of granite for the purposes of separating zircons for radiometric dating.

The standard methodology to separate accessory minerals including zircon from granite is to mechanically break it down to a sand grain size in a ring mill, and use successive heavy liquids to isolate the mineral you are after. Luckily for radiometric dating, zircon, the target mineral, is dense and easily separated from the less dense minerals.



symboom - 8-10-2017 at 20:29

Doesnt hot phosphoric acid react with the SiO2 grannite

Melgar - 8-10-2017 at 23:41

Quote: Originally posted by symboom  
Doesnt hot phosphoric acid react with the SiO2 grannite

Only when it's really, really hot. Like, elemental-phosphorus-generating temperatures. Hot sodium hydroxide solution might work better, as it would form soluble sodium silicate, slowly. Something stainless steel should suffice, since glassware obviously wouldn't hold up.

unionised - 9-10-2017 at 02:04

Quote: Originally posted by Melgar  
Quote: Originally posted by symboom  
Doesnt hot phosphoric acid react with the SiO2 grannite

Only when it's really, really hot. Like, elemental-phosphorus-generating temperatures. Hot sodium hydroxide solution might work better, as it would form soluble sodium silicate, slowly. Something stainless steel should suffice, since glassware obviously wouldn't hold up.

Phosphoric acid attacks "fused quartz" at temperatures over 150C
It's not clear at what temperature it will start to react with crystalline silica but I imagine that the transition between alpha and beta quartz near 573 C would bring about reaction if H3PO4 was present.
If you get granite to the temperatures used in phosphorous production (about 1500C), it will melt. In those circumstances most things you might have been looking for will be destroyed anyway.
I don't see why anyone thinks you need to get it that hot to react it with H3PO4.

barbs09 - 9-10-2017 at 04:37

You after monazite?

Melgar - 9-10-2017 at 08:59

Quote: Originally posted by unionised  
Phosphoric acid attacks "fused quartz" at temperatures over 150C
It's not clear at what temperature it will start to react with crystalline silica but I imagine that the transition between alpha and beta quartz near 573 C would bring about reaction if H3PO4 was present.

Well, at any of these temperatures, there will be no H3PO4 anyway, if you want to get pedantic, since it'd all be metaphosphate. But how would (meta)phosphoric acid even react with silica? They're both acidic. Maybe it will dissolve silica at high temperatures, but the only actual reaction that I'm aware of is the phosphorus reduction one, in which carbon, silica, and (meta)phosphate react at high temperatures.

unionised - 9-10-2017 at 12:53

Quote: Originally posted by Melgar  

... But how would (meta)phosphoric acid even react with silica? ... but the only actual reaction that I'm aware of...


You might try learning some chemistry.
Silicon forms phosphates
http://pubs.acs.org/doi/abs/10.1021/ja9813461?journalCode=ja...

http://www.sciencedirect.com/science/article/pii/S0022459612...

In nay event, in the real world, fused quartz is attacked by phosphoric acid at relatively low temperatures.

Melgar - 11-10-2017 at 03:32

Quote: Originally posted by unionised  

You might try learning some chemistry.

You're one to talk, Mr. "Boric acid is VERY toxic". :P
Quote:
Silicon forms phosphates
http://pubs.acs.org/doi/abs/10.1021/ja9813461?journalCode=ja...

http://www.sciencedirect.com/science/article/pii/S0022459612...

We're not talking about silicon, we're talking about silica.
Quote:
In nay event, in the real world, fused quartz is attacked by phosphoric acid at relatively low temperatures.

And in the real world, boric acid is about as toxic as table salt. (Sorry. I just had deja vu. ;) ) And indeed, glass and fused quartz are attacked by molten phosphoric acid. But in my response, I was implying that it probably isn't a chemical reaction, so much as the fact that polyphosphoric acid is glass-like, and as a result can mix with glass and dissolve it. This is not an actual reaction, any more than dissolving sugar in water is a reaction. Since you wanted to get pedantic, I took issue with your use of the word "react".

[Edited on 10/11/17 by Melgar]

unionised - 14-10-2017 at 11:12

Quote: Originally posted by Melgar  
Quote: Originally posted by unionised  

You might try learning some chemistry.

You're one to talk, Mr. "Boric acid is VERY toxic". :P
Quote:
Silicon forms phosphates
http://pubs.acs.org/doi/abs/10.1021/ja9813461?journalCode=ja...

http://www.sciencedirect.com/science/article/pii/S0022459612...

We're not talking about silicon, we're talking about silica.
Quote:
In any event, in the real world, fused quartz is attacked by phosphoric acid at relatively low temperatures.

And in the real world, boric acid is about as toxic as table salt. (Sorry. I just had deja vu. ;) ) And indeed, glass and fused quartz are attacked by molten phosphoric acid. But in my response, I was implying that it probably isn't a chemical reaction, so much as the fact that polyphosphoric acid is glass-like, and as a result can mix with glass and dissolve it. This is not an actual reaction, any more than dissolving sugar in water is a reaction. Since you wanted to get pedantic, I took issue with your use of the word "react".

[Edited on 10/11/17 by Melgar]

You seem to be quoting someone as saying "Boric acid is VERY toxic"
Who are you claiming said it?

We're not talking about silicon, we're talking about silica.
So?
Silica reacts with phosphoric acid to produce silicon phosphate in much the same way that magnesia reacts with phosphoric acid to make magnesium phosphate.
You were inaccurately claiming that no such reaction could take place with silica.

"boric acid is about as toxic as table salt"
Probably.
Both have very low acute toxicity, but both are chronically toxic.
It's the chronic effect of borates that got them banned in the EU and it's the chronic effect of salt that is causing people to campaign to reduce the amounts of it in food.

" But in my response, I was implying that it probably isn't a chemical reaction, "
you were implying that, but you were wrong- you didn't know enough chemistry to recognise it.

"This is not an actual reaction, any more than dissolving sugar in water is a reaction."
Yes it is- you just don't know the chemistry (I'm getting a sense of deja vu about this)

"Since you wanted to get pedantic, I took issue with your use of the word "react". "
Indeed, you did.
Foolish of you, wasn't it?
You took issue with reality.
That... doesn't usually go well.

Incidentally, molten glasses don't always mix. I don't know whether phosphate glasses mix with silicate ones.
Borate glass and silicate glass don't mix/ dissolve when molten.

Melgar - 16-10-2017 at 16:31

It was definitely you that warned of boric acid's considerable toxicity. Or it was someone else that likes to respond "In the real world..." and then follow that with something that is not actually true in the real world.
Quote: Originally posted by unionised  
Silica reacts with phosphoric acid to produce silicon phosphate in much the same way that magnesia reacts with phosphoric acid to make magnesium phosphate.
You were inaccurately claiming that no such reaction could take place with silica.

I never denied that silicon phosphates can form, presumably from the reaction of silicon with phosphoric acid. No idea what the structure would be, though presumably it'd be like other metal phosphates? I only questioned whether they could form by reacting polyphosphoric acid with silica at high-ish temperatures. I've prepared silica-gel-supported phosphorus pentoxide plenty of times, and it sort of melts into a glassy amorphous solid, very slowly. Maybe "silicon phosphate" is an alternate/incorrect name for this stuff, because all my searches turned up the term "silica phosphate" and not "silicon phosphate".

Actually, "silica phosphate" seems to be exactly what's forming when phosphoric acid and silica combine at high temperatures. Contrast the papers you linked, which don't describe the reaction you're proposing at all, with this paper, which describes exactly the phenomenon you're talking about, and also doesn't refer to it as a "reaction", at least in the abstract:

http://www.icevirtuallibrary.com/doi/abs/10.1680/cfec.31784....

DraconicAcid - 16-10-2017 at 16:43

I don't know much about phosphates, but I'd suspect that any reaction between phosphates and silica would result in silicophosphates....you'd get complex polysilicate chains with phosphorus replacing some of the silicon atoms, or a complex polyphosphate with some of the phosphorus atoms replaced with silicon. I definitely wouldn't call it a silicon phosphate, any more than I would call borosilicate glass a boron silicate.

unionised - 17-10-2017 at 12:42

Quote: Originally posted by Melgar  
It was definitely you that warned of boric acid's considerable toxicity. Or it was someone else that likes to respond "In the real world..." and then follow that with something that is not actually true in the real world.
Quote: Originally posted by unionised  
Silica reacts with phosphoric acid to produce silicon phosphate in much the same way that magnesia reacts with phosphoric acid to make magnesium phosphate.
You were inaccurately claiming that no such reaction could take place with silica.

I never denied that silicon phosphates can form, presumably from the reaction of silicon with phosphoric acid. No idea what the structure would be, though presumably it'd be like other metal phosphates? I only questioned whether they could form by reacting polyphosphoric acid with silica at high-ish temperatures. I've prepared silica-gel-supported phosphorus pentoxide plenty of times, and it sort of melts into a glassy amorphous solid, very slowly. Maybe "silicon phosphate" is an alternate/incorrect name for this stuff, because all my searches turned up the term "silica phosphate" and not "silicon phosphate".

Actually, "silica phosphate" seems to be exactly what's forming when phosphoric acid and silica combine at high temperatures. Contrast the papers you linked, which don't describe the reaction you're proposing at all, with this paper, which describes exactly the phenomenon you're talking about, and also doesn't refer to it as a "reaction", at least in the abstract:

http://www.icevirtuallibrary.com/doi/abs/10.1680/cfec.31784....


You are not looking in the right places if you think silicon phosphate is the wrong term.
you may not know that structure and thus think it's an amorphous product.
In the real world it's fairly well characterised.
The fact that someone published a paper about a "new" structure tells you that there was already an established structure. That's why I chose that paper to show you.
It's a pity you didn't understand.
"I only questioned whether they could form by reacting polyphosphoric acid with silica at high-ish temperatures. "
No, you didn't"question" it, you said it didn't happen- and you remain wrong about that. Remember, you said " But how would (meta)phosphoric acid even react with silica? They're both acidic" (I know there's a question mark in there- it was plainly rhetorical)
It's as if you don't understand amphoteric behaviour. It's some chemistry you could learn.

Your opening gambit was "Only when it's really, really hot. Like, elemental-phosphorus-generating temperatures."
And that's still wrong.

And, perhaps you would be so kind as to point out where you got this idea "It was definitely you that warned of boric acid's considerable toxicity. "
I mean, yes, it is worthy of consideration- and then I pointed out that I don't have a problem with supervised kids playing with it.


[Edited on 17-10-17 by unionised]

clearly_not_atara - 17-10-2017 at 13:47

Silicon phosphate is indeed a mixed glass rather than a traditional salt; the stoichiometry is Si5O(PO4)6:

http://www.sciencedirect.com/science/article/pii/S0020169300...

However as this paper demonstrates the rxn occurs at ordinary temperatures. The chemistry of silicon phosphate is more comparable to that of aluminium silicate than it is to aluminium sulfate.

Perhaps more importantly, phosphoric acid is not a very good tool for solubilizing silicon dioxide in water. Which is the actual topic of this thread. The product of reacting phosphoric acid with silicate rock is still solid and still insoluble, so it does not do a whole lot of good. For dissolving silicates there are essentially two options:

* excess alkali
* hydrofluoric acid

I recommend the former.

There is another way to degrade silicate rock for analysis which may be of interest: supercritical carbonation. Rxn of finely ground rock with supercritical CO2 can IIRC convert the alkali components to their carbonates leaving behind the poor metals. The alkali carbonates can be removed by simple water extraction. However this process requires substantial equipment.

Melgar - 17-10-2017 at 21:17

Quote: Originally posted by unionised  
You are not looking in the right places if you think silicon phosphate is the wrong term.
you may not know that structure and thus think it's an amorphous product.
In the real world it's fairly well characterised.
The fact that someone published a paper about a "new" structure tells you that there was already an established structure. That's why I chose that paper to show you.
It's a pity you didn't understand.
"I only questioned whether they could form by reacting polyphosphoric acid with silica at high-ish temperatures. "
No, you didn't"question" it, you said it didn't happen- and you remain wrong about that. Remember, you said " But how would (meta)phosphoric acid even react with silica? They're both acidic" (I know there's a question mark in there- it was plainly rhetorical)
It's as if you don't understand amphoteric behaviour. It's some chemistry you could learn....

Ok, let me get this straight. After you claimed that metaphosphoric acid would react with glass and silica, I asked how silica and metaphosphoric acid could react to produce a new compound. You responded by citing two papers describing compounds that contain both silicon and phosphate, but are clearly not formed by reacting silica with metaphosphoric acid. You triumphantly declare victory, regardless of the relevance of the information you cited. I further emphasize that I don't give a fuck about some exotic phosphate of silicon that was first prepared in the 1990s. I care about what, if any, reaction occurs under the conditions described earlier. You then picked out my dismissal of silicon phosphates as meaning that I don't understand how such a compound could exist? Really, it's because I just don't care if such a compound exists or not, since it'd be completely useless and unobtainable to me for the foreseeable future anyway. But it's like every time I try to get you back on topic, you keep responding with totally irrelevant talk about silicon phosphate.

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clearly_not_atara - 18-10-2017 at 12:03

https://www.geopolymer.org/fichiers_pdf/CemPlant.pdf

Apparently some organic chelators can attack feldspar.

[Edited on 18-10-2017 by clearly_not_atara]

symboom - 18-10-2017 at 12:23

Ah molten phosphoric acid solid phosphoric acid melts at 50 C
And boils 158 °C

Also cesium hydroxide is a powerful agent that will also dissolve silicon dioxide in liquid form and I wouldnt mess with molten.



unionised - 18-10-2017 at 12:40

Quote: Originally posted by clearly_not_atara  
Silicon phosphate is indeed a mixed glass rather than a traditional salt; the stoichiometry is Si5O(PO4)6:

http://www.sciencedirect.com/science/article/pii/S0020169300...

However as this paper demonstrates the rxn occurs at ordinary temperatures.

OK
Here's the abstract

"Silicon phosphate samples have been synthesized at low temperature (200–300 °C) and characterized using various physico-chemical methods. The crystal structure of the silicon phosphate prepared at low temperature and the sample heated at 1000 °C was studied by the Rietveld method. The crystals belong to the hexagonal space group R3 with a ⋍ 7.8 and c ⋍ 24.0 Å. The structure of silicon phosphate in both of these samples is found to be Si5O(PO4)6. The asymmetric unit consist of three crystallographically independent silicon atoms of which one is in a tetrahedral environment and the other two have octahedral coordination."

Let's just clarify that
"Silicon phosphate ...The crystal structure of the silicon phosphate pr... The crystals belong to the hexagonal space group. The structure of silicon phosphate ... three crystallographically independent ..."

That's a whole bunch of references to it being crystalline.
You can't assign a space group to something that's not crystalline; and they tell you what the space group is.

And, on that basis you say it's a glass.

Why do you do that?

unionised - 18-10-2017 at 12:52

Quote: Originally posted by Melgar  
... You responded by citing two papers describing compounds that contain both silicon and phosphate, but are clearly not formed by reacting silica with metaphosphoric acid. ... I further emphasize that I don't give a fuck about some exotic phosphate of silicon that was first prepared in the 1990s. ..



I see you accept you were wrong about borate. I guess that's a start.

Kicking around the house somewhere I have a copy of this book - published in 1978
https://books.google.co.uk/books?id=V_vvAAAAMAAJ&q=inorg...


It talks of the production of silicon phosphate from phosphoric acid and silica (or glass) and it mentions the stoichiometry + properties. If I get round to it, I will dig it out + quote it verbatim. The stuff wasn't new then.

In the real world 1978 is before the 1990s


However, and here's the important point, any product formed from phosphoric acid and silica at a moderately high temperature was enough to show that they damned well do react and your lack of understanding of the product won't ever have stopped them.
You don't need to get it as hot as you bizarrely claimed- do you?



[Edited on 18-10-17 by unionised]

clearly_not_atara - 18-10-2017 at 16:51

Mixed oxide, sorry, not mixed glass. Point is it's not a "salt" in the ionic sense, which means it does not dissolve in water, which is the actual. topic. of. the. thread. And I am not always specific when something is not the point. Although, you could probably make it into a glass if you froze it quickly enough, being that's all a glass is. But yes, continue snipping about grammar, and I will continue to find references which are actually related to the hydrolysis of granite.

Carbon dioxide and water, 200 C:

http://www.sciencedirect.com/science/article/pii/00167037769...

unionised - 19-10-2017 at 11:18

Quote: Originally posted by clearly_not_atara  
I will continue to find references which are actually related to the hydrolysis of granite.


That's nice.
Do you plan to come back later and address what the OP asked for which was
"what I could do for degradate and separate granite components."
The reason I ask is that fairly hot phosphoric acid will actually do that.

SWIM - 19-10-2017 at 13:27

Maybe if you just leave the granite sample here on this thread it will be decomposed by pure orneryness.

Melgar - 19-10-2017 at 17:12

Quote: Originally posted by unionised  
The reason I ask is that fairly hot phosphoric acid will actually do that.

You assumed that, you never actually attempted it or tested it or found a source that did either of those things. Granite is a lot more complex than silica too, so there's every reason to believe that this doesn't have a chance of working.

I'm not super worried about you derailing the thread, because all the good ways to separate components have already been mentioned, but there is still one bad suggestion that needs to be put to rest.

I attached the source I posted earlier, which I assume you didn't read. Page 2, third paragraph. I tried to copy and paste it, but the formatting was messed up due to the PDF.

Attachment: silicAphosphate.pdf (485kB)
This file has been downloaded 289 times

DraconicAcid - 19-10-2017 at 18:23

Quote: Originally posted by Melgar  
Quote: Originally posted by unionised  
The reason I ask is that fairly hot phosphoric acid will actually do that.

You assumed that, you never actually attempted it or tested it or found a source that did either of those things. Granite is a lot more complex than silica too, so there's every reason to believe that this doesn't have a chance of working.


It might also mean that it will react with the quartz bits and not the other bits.

unionised - 20-10-2017 at 14:13

Quote: Originally posted by Melgar  
Quote: Originally posted by unionised  
The reason I ask is that fairly hot phosphoric acid will actually do that.

You assumed that, you never actually attempted it or tested it or found a source that did either of those things. Granite is a lot more complex than silica too, so there's every reason to believe that this doesn't have a chance of working.




Phosphoric acid attacks silica.
The silica in granite is not "magic" silica that somehow resists attack.

Melgar - 20-10-2017 at 14:49

Quote: Originally posted by unionised  

Phosphoric acid attacks silica.
The silica in granite is not "magic" silica that somehow resists attack.

And phosphoric acid is not some sort of "magic" acid that can dissolve the silica on the inside from the outside. It's also not the same thing as "fused quartz", which is amorphous. Depending on the silica content of the granite, there's a very good chance of just etching the outside of the rock a little a bit, leaving the inside untouched. Not to mention, metaphosphate is solid, and the higher its silica content, the less water-soluble it becomes.

unionised - 21-10-2017 at 02:58

Thanks for explaining why it's' kind of traditional to grind stuff to powder before seeking to dissolve it.

Incidentally, the data I can find say thing like "The silica content of granite should be at least 70%"
From
http://www.devonmemorials.co.uk/memorialmaterials.html
Which suggests that even bulk granite should be fairly susceptible to dissolution.

unionised - 29-10-2017 at 01:02

I got round to digging out that book + checked the references.
The reaction of silica with phosphoric acid was reported somewhat earlier than the 1990s.

"Sur une combinaison d’acide phosphorique et de silice ; par MM. P. Hautefeuille et J. Margottet"

https://fr.wikisource.org/wiki/Comptes_rendus_de_l%E2%80%99A...

Though it's hard to see why it matters when it was reported; it happens.

clearly_not_atara - 30-10-2017 at 00:11

Quote: Originally posted by unionised  
Quote: Originally posted by clearly_not_atara  
I will continue to find references which are actually related to the hydrolysis of granite.


That's nice.
Do you plan to come back later and address what the OP asked for which was
"what I could do for degradate and separate granite components."
The reason I ask is that fairly hot phosphoric acid will actually do that.

Dissolving does that better than anything else. There's no reason to believe that the rxn product of granite with phosphoric acid will be easy to separate into components, or anything other than a solid concretion, for that matter. None of the references you've linked say anything like this at all. I looked up dozens of papers on granite analysis; phosphoric acid was never mentioned.

Congratulations, phosphoric acid reacts with silica. Who says it doesn't also react with every other component of granite? It reacts with all of the metal oxides; you go from a mixture of silicates to a mixture of phosphates. How precisely does converting insoluble silicates to insoluble phosphates allow you to separate them into components?

Phosphates are insoluble, therefore not useful. Dissolving things allows for differential precipitation, it allows you to actually get something from the granite; you've diverted this thread into "does silicon phosphate exist?" and you know it. Which is why you have chosen to post yet another irrelevant paper about the reaction of phosphate with silica instead of a paper about the reaction of anything at all with granite.

Alkaline hydrolysis is still the best actual solution to the actual problem being posed here.

[Edited on 30-10-2017 by clearly_not_atara]