Sciencemadness Discussion Board - Silica Gel

Silica Gel

SAM4CH - 30-11-2008 at 07:07

I'd like to prepare Silica gel from sodium silicate, but I faced a problem in HCl/Sodium silicate method, I got very weak structure not like in chemical store Silica gel.
I need perfect procedure for preparing it.

Klute - 30-11-2008 at 08:53

Well, considering that it is a gel, you will not obtain hard pebbles like the dessicant, more a fine flowing powder.

You can obtain lumps by not letting the gel fset, that is just after reaching neutral (stop before acidic), filter the slush immediatly and leave to dry. You will have largish lumps that crumble easily after activation. I don't think the adsorption properties are at their maximum with such material, it has some surprisingly different properties than "true" silica gel, surely because it has a much smaller specifc surface.

If you add more acid to the slush until pH is acidic, and keep on stirring, the slush will form a gel. leave it to set for 15-60min, then decant wash, decant wash, etc and finally filter and wash generously. You obtain a free flowing powder after activation, with a much higher specific surface.

I don't know how they produce the dessicant shard in the industry though. Try looking into some patents.

S.C. Wack - 30-11-2008 at 10:08

"...silica gel is converted to pelletized or granular form by extruding pulverized gel with a binder or by shaping the hydrogel during drying. Silica can be gelled in spherical form by spray-drying, or by spraying droplets into an immiscible liquid (emulsion polymerization). Freezing of a silica sol produces silica gel particles of nonspherical shapes." - K-O.

Have fun doing that. Nothing in K-O or Ullmann's looks very convenient except for the original method.
US1297724

kmno4 - 30-11-2008 at 15:42

Quote:

Originally posted by SAM4CH
I'd like to prepare Silica gel from sodium silicate, but I faced a problem in HCl/Sodium silicate method, I got very weak structure not like in chemical store Silica gel.
I need perfect procedure for preparing it.

Inorganic Syntheses vol.2, page 95 (available)
V. Karyakin and I. I. Angelov, Pure Chemical Compounds [in Russian] (available as DJVU in Russian), page 173
Do not search in shitty patents - above is given good literature

ps. making this gel is a fun - you stirr a liter of solution and in a moment you cannot sir: you got a hard gel.

chief - 1-12-2008 at 12:48

Was it not possible to somehow prepare the Na-silicate by melting SiO2 (quartz) with either NaOH OR Na2CO3, and then dissolving in H2O ? This could be done with a welding-transformer and some carbon-electrodes.

Such gel is very useful: It wets glass, eg. . Also fireproof furnaces etc. may be made with the gel as binder.

Klute - 1-12-2008 at 14:39

IIRC, even boiling glass in conc. NaOH gives a silicate solution after a certain period. But you just aswell get it from the nearby hardware store, I think it's pretty universally used and sold.

starman - 2-12-2008 at 02:11

Quote:

Originally posted by Klute
IIRC, even boiling glass in conc. NaOH gives a silicate solution after a certain period. But you just aswell get it from the nearby hardware store, I think it's pretty universally used and sold.

Cool...off to the hardware store.Sold and used for what?Trade names?

Klute - 2-12-2008 at 09:10

trade names I dunno they will surely be different from country to country... It used a a hydrofuge for wood, bricks, etc a very dense viscous clear liquid. Asking for waterglass will surely be all that's needed.

Lloyd - 28-1-2009 at 05:45

Quote:

Originally posted by starman

Quote:

Cool...off to the hardware store.Sold and used for what?Trade names?

in oz i'm pretty sure that sodium silicate has uses in the 'temporary automotive head repair in a bottle',i hope this helps.

starman - 28-1-2009 at 07:50

Thanks Lloyd,oz specific sources always welcome.We always seem to have to go that extra yard here in oz.