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Re: BBA and P


On Thu, 25 Nov 1999, Sylvia wrote:
 
> This discussion of phosphate removers seems to conflict with the information 
> given on the Kent Phosphate Sponge container. The Seachem website states that 
> the 2 phosphate removers are iron oxide and aluminum oxide. The Phosphate 
> Sponge jar states that other products will release soluble aluminum compounds 
> into the water, which their product does not, though it is white in color (as 
> the faq reports the aluminum oxide products are). I inferred that it is not 
> the same type of medium as the aluminum oxide . . .

The true oxides of iron (the mineral hematite) and aluminum (the mineral
corundum-one of the hardest materials known) are pretty non-reactive.  I
suspect that the Kent product is aluminum hydroxide or oxyhydroxide. The
issue seems to be whether their product releases more or less aluminum
then somebody else's similar aluminum hydroxide or oxyhydroxide product.  
I suppose that it's possible for there to be a difference.

> Unfortunately, Kent 
> Marine took an early holiday, and I couldn't reach anyone there today to get 
> more information on this, nor do they seem to have a web site. Forgive me for 
> being ignorant on this matter, but does a ceramic medium contain aluminum 
> oxide?

"Ceramic" may be an overworked term here.  I think it can be used for any
sort of solid material aggregated from non-metallic raw materials and
bound by reactions that occur during heating.  In that context there are a
lot of materials that can be put into a ceramic, including aluminum
hydroxides.  Aluminum oxide (not hydroxide) ceramics can be *extremely*
hard, durable and non-reactive, but expensive.  It's good for things like
mortars; not very good for things like phosphate adsorbers.

> I am a bit confused about the use of ceramic beads used in purifying 
> and deionization and the "ceramic" medium in the phosphate sponge. . . It 
> sounds suspiciously similar, and therefore would not be rechargeable. What 
> are the possible consequences of this use in the tank? (I mentioned earlier a 
> rise in pH and cloudiness)? 

The purifying and deionizing materials I know of are plastics (usually,
modified polystyrene), not ceramics.  That aside, I have used the Kent
product and I tried to recharge it per their instructions.  The package
instructions weren't very encouraging about the recharging working well,
and it didn't.

I think that the "sponge" can't be recharged if it's adsorption capacity
was used up with phosphorus or silica.  It probably is possible to
recharge the stuff if the adsorption capacity is lost instead to
biological fouling or to adsorption of organic molecules that can be
burned off.

It's common for silica to be 100 times more common in water than
phosphorus - often more.  When the phosphorus sponge (of any manufacture)
loses its capacity it's probably more likely to lose it to silica than it
is to lose it to phosphorus.  If you want to remove silica that's
great. If you want to remove phosphorus that's a Bad Thing.


Roger Miller