DerAlte - 13-8-2007 at 22:20
Anyone ever heard of this 'Activated Clay' as a dessicant? I got a bag (about 2 oz.) of this stuff in a package of equipment originating from Taiwan,
I believe. It seems to be a Ca, Mg, Na, etc, hydrated silicate. Allied to bentonite apparently. Does it work like silica gel?
Regards,
Der Alte.
Ozone - 14-8-2007 at 15:11
Yes! It is also (with bentonite) known as--cat litter! It sucks up the pee and turns into rocks which are easily scoopable from the box. It is also
very handy when a bunch of aqueous fluid gets spilled in your car trunk--put some down, wait a day, and scoop it out.
As per Si(OH)x, I don't know.
I do not know about the efficiency of these materials as dessicants, but I can vouge for high capacity.
It might be interesting to saturate some, dry it back out , and see how well it does then.
Cheers,
O3
not_important - 14-8-2007 at 16:41
Ozone has it, it's a montmorillonite type clay. High surface area with lots of oxygens and hydroxyl groups means that water plates out on the
surfaces of the clay.
Clays usually are only good to 50 C or so, after that the drying capacity drops off sharply and reverses so that the clay is releasing absorbed water.
Heating to 100 C of so will drive off much of the water; 150 C and reduced pressure will fully regenerate them. Too high of heat can cause changes in
the physical structure resulting in reduced capacity.
They're OK at higher humidities, but become less efficient than other desiccants at lower amounts of water vapour.
Actually getting it wet might also mess it up, as again pores could be closed up, reducing the surface area.
http://www.sorbentsystems.com/desiccants_charts.html
DerAlte - 15-8-2007 at 23:00
Thanks! Sounds like it behaves much like silica gel. Those graphs were rather useful, not_important. Never realized silica gel could absorb so much
water. There's a short piece on desiccants in CRC Phys&Chem. that shows the ultimate performances of some common ones. Good old CaSO4 rates pretty
welll for ultimate vapor pressure, even if idoesn't absorb much.
Regards,
Der Alte.
not_important - 16-8-2007 at 00:33
Here's another handy chart, similar to the CRC one
http://www.mallbaker.com/techlib/documents/americas/3045.htm...
as far as ultimate level or dryness goes, CaSO4 is almost as good as H2SO4, H3PO4, and Al2O3. For general drying the sulfates Ca, Mg, and Na are a
good choice - cheap, low toxicity and reactiveness, not too hard to regenerate; MgSO4 can act as an acid in some cases, especially if heated too hot
during activation/regeneration.
DerAlte - 17-8-2007 at 12:53
Great info., not_important! Added to my pile... Der Alte