Reef Chemistry Question of the Day #126 Aluminum Oxide

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#126[/HASHTAG]

Two of the primary materials used as inorganic binders of phosphate are GFO (granular ferric oxide) and aluminum oxide. GFO is always a dark color, varying from orange to red to nearly black, depending on hydration and possibly other factors. Aluminum oxide binders are always white.

What is the chemical formula for the aluminum oxide used as a phosphate binder?

A. AlO
B. AlO2
C. Al2O
D. Al2O2
E. Al2O3
F. Al3O2
G. Al3O3

Bonus: why is that the formula?

Good luck!































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[Downbeach]

E
A compound made up of aluminum and oxide.

 

[redfishbluefish]

I know this one.....use to work on Technecium 99m Generators that contained Alumina (Aluminum Oxide) and actually was supplied in nice aluminum canisters. I probably still have some of these empty canisters in the basement somewhere. Jim (downbeach), has the formula above, but the reason for the formula is because ionically Al is 3+ while O is 2-......and everything needs to balance out. So 2 Al's = 6+, and 3 O's = 6-, and everybody is happy!

 

[beaslbob]

c

(means I don't know) LOL

 

[Randy Holmes-Farley]

And the answer is...E. Al2O3

In seawater in contact with air, aluminum salts will always be in the Al+++ state and oxygen salts will be in the O-- state. In a sense, the aluminum always looses its three valence electrons and the oxygen picks up two extra valence electrons. Any other combination would shift some electrons between the aluminum and oxygen ions to arrive at this stable configuration.

In order to combine them in a way that maintain charge neutrality on the solid (always the case for any solid), you need two Al+++ ions (giving +6) and three O-- (giving 6-).


Happy Reefing!

 

[Shaun Sweeney]

Trying to figure out how much gfo to load into my reactor given 160 gallons of water.

 

[Downbeach]

Trying to figure out how much gfo to load into my reactor given 160 gallons of water.

If you're using the regular granular GFO, 2 1/2 cups is what's recommended, if the HC then 1 1/4 cups. In either case I wouldn't start out with the whole amount. I would start with 1 cup of the regular or 1/2 cup of the HC, and closely monitor the results, you don't want to strip your system of PO4. What are you using to measure PO4? This is one test I think a Hanna meter would be best.

 

[Shaun Sweeney]

Many thanks Jim. I'm now wondering about the kind of reactor that best suits the GFO. I experimented with a CPR Nano Tumbler that I picked up at MACNA but had to make my own fines filter top as the particles are just to small. I have a full size reactor that I should probably try next.