[bodegas]

Hello everyone, I'm new to this forum but I'd really like your help.

I've been working with zeolites and I've found most of them terribly unstable at low pH, below pH 3 zeolites NaX and NaA just dissolve.
My problem now is that I need to destroy a zeolite so I can analyse everything that was trapped inside. The problem seems to be that this zeolite has a higher ratio of Si/Al (about 15) and so, is more stable to attacks from acids. I've used HNO3 at 65% and high temperatures and pressures, but I can't seem to get the job done.
I've been considering using a strong oxidizer but I'm afraid that the bonds are strong enough to withhold.
Could anybody throw an opinion?

[Alberto_Kravina]

Maybe you could just precipitate the Al of the zeolithe with hydroxide. but I'm not really sure about this, I'm not an expert in this field.

[hmx9123]

If you can get it hot enough, it may go to its thermodynamic sink.  Try heating it in a muffle or tube furnace to 1000C or so.  If not, you could always hit it with a methane/oxygen torch.  That'll get it to around 1800-2000C if you have the right fuel air mix.

[bodegas]

The problem is that, as I said, I need to analyse what is trapped inside the zeolite, so I need to keep it in an aqueous phase.
I'm guessing that most of the Al has gone away with the HNO₃ and what I have now is basically a three-dimensional structure made of silicates. Basically, I think I have some sort of sand. Is anything strong to dissolve sand?
I know that HF attacks glassware, which, I guess, is basically a polisilicate structure. Maybe I can use the same principle to destroy the zeolite.

[Alberto_Kravina]

I know that HF attacks glassware, which, I guess, is basically a polisilicate structure. Maybe I can use the same principle to destroy the zeolite.

It attacks glass, yeah, but it takes a bit long until the glass (silicate) completely dissolves.
Also, HF is a pretty nasty stuff, as well as SiF₄, which is produced in this reaction. Be careful if you make this reaction

[bodegas]

Thanks for the tip

Could somebody tell if teflon is stable enough towards attack from HF to make the reaction inside a teflon vase?

[Alberto_Kravina]

HF is normally stored in plastic recipients, I think that Polyethylene is enough, teflon should also work. :=
Be careful not to get HF on your hands. I don't know what exactly happens but it is dangerous!!!

[P]

"I don't know what exactly happens but it is dangerous!!!"

Yes it is.  It seeps through your flesh and de calcifies your bones  -  supposidly very painfull and and possibly fatal depending on the amounts.  It is reccomended to have some calcium  glutomate at hand if you are working with the stuff (In fact it is reccomended not to use the stuff at all unless you really know what you are doing with it).  I think it's calcium glutomate  -  check it out yourself - esspecially if you are going to use it.

Any case - do LOTS of reading arround the subject of HF and the health and safety issues associated with it before even thinking about it.

[plu]

Could somebody tell if teflon is stable enough towards attack from HF to make the reaction inside a teflon vase?

Yes, teflon is the recommended material for the containment of HF.

[bodegas]

thank you all for the advice

Allready done the reaction, luckily it only needed a very small amount of HF. Worked just fine

[tesseract]

re: HF

..  It is reccomended to have some calcium  glutomate at hand if you are working with the stuff (In fact it is reccomended not to use the stuff at all unless you really know what you are doing with it).  I think it's calcium glutomate  -  check it out yourself - esspecially if you are going to use it.

It's calcium gluconate, but otherwise, yeah, HF is very nasty stuff.