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Re: phosphate removal products

>
>
>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.


The Kent product is not aluminum hydroxide (soluble in alkaline water 
and turns into a gel in water). The Kent product is simply pulverized 
aluminum oxide, it's the same as every other one out there. I do not 
understand the origin for their dissolved aluminum compounds claim... 
If they have some experimental data I wish they would share it with 
the rest of us. Aluminum oxide is totally and completely insoluble in 
water, so I can not see where these compounds could be coming from; 
their claim simply makes no sense from a scientific standpoint.

>
>  > 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


Not only overworked, but misused here. The Kent product is not a 
ceramic. I guess they say that because it sounds "cool" and it 
certainly seems like a ceramic (very hard isn't it)? but the hardness 
stems from the fact that aluminum oxide (corundum as you point out 
above) is one of the hardest minerals known. It's a harmless claim 
since the product still does what it says it does.

>
>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.
>

You are correct, it cannot be recharged because the adsorption of 
phosphate or silicate to the material is an irreversible covalent 
reaction... which brings me to another point: no phosphate remover 
will leach phosphate back into the water when exhausted... the level 
goes up when exhausted because phosphate is still being made but now 
not removed. Here's a simply test to prove it, remove your phosphate 
remover when done and rinse thoroughly (to remove any residual tank 
water) and place it in some fresh water in a jar and let sit... test 
it after a few days... you won't see a bit of phosphate in the water. 
With respect to "recharging" it to drive off organic material... I 
suppose that is technically a possibility, although in practice it 
would be insignificant as the material has a very low organic 
affinity.

This whole heating to regenerate is based on the fact that when used 
in the application of gas filtration (to remove moisture from air) 
aluminum oxide can be regenerated by heating to drive off the 
adsorbed water... but in the application of phosphate/silicate 
removal, heat has no affect whatsoever.

I hope this doesn't appear to be "bashing" of another product. That 
truly is not my intent, but I do feel strongly when another 
manufacturer tries to mislead the consumer (either intentionally or 
not, I don't know) with pseudo scientific claims that prop up invalid 
assertions of product superiority.

-Greg Morin


Gregory Morin, Ph.D.  ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc.      www.seachem.com     888-SEACHEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~