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Unread 11/04/2014, 07:48 AM   #101
Randy Holmes-Farley
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One additional point bears telling since it suggests to folks who have elevated aluminum, whether from media like Phosguard, the Marine Pure Ceramic Biomedia, or from other sources, how to reduce it...

Ehsan (owner? of Triton) suggested that folks should alternate between aluminum oxide phosphate binders and GFO, in part because the GFO binds the aluminum released from the aluminum oxide and keeps it in check.

Assuming this is true (and I have not independently verified it, but they certainly have access to lots of test results), it suggests that folks who want to use aluminum-containing media for whatever reason might usefully use GFO as their phosphate binder, and keep aluminum in check at the same time.

It also suggests the aluminum is not particulate but rather individual ions that can bind to GFO, but I'll stop beating that dead horse.


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Unread 11/04/2014, 08:05 AM   #102
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One additional point bears telling since it suggests to folks who have elevated aluminum, whether from media like Phosguard, the Marine Pure Ceramic Biomedia, or from other sources, how to reduce it...
OK, can you conclude that it's safe for FO/FOWLR? You better say yes.


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Unread 11/04/2014, 08:17 AM   #103
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mikeatjac,

I to run a reactor with Seachem matrix. I mainly used seachem version because of price and the fact that I can run it in reactor and not take space in sump (also have been using it for 5 years on discus tank in a canister).

My question for the Chemistry gurus is the following.

How likely is it that other cermic based bio medias contain aluminium oxide (like seachem matrix, Eheim SUBSTRAT, etc).


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Unread 11/04/2014, 08:27 AM   #104
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mikeatjac,

I to run a reactor with Seachem matrix. I mainly used seachem version because of price and the fact that I can run it in reactor and not take space in sump (also have been using it for 5 years on discus tank in a canister).

My question for the Chemistry gurus is the following.

How likely is it that other cermic based bio medias contain aluminium oxide (like seachem matrix, Eheim SUBSTRAT, etc).
I just don't know. There are a number of materials it could be made from. Sorry.

If you don't observe any unexpected issues, then I wouldn't change from it without a more substantial reason (which might include an significantly elevated aluminum measurement, if you got one).


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Unread 11/04/2014, 08:28 AM   #105
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OK, can you conclude that it's safe for FO/FOWLR? You better say yes.
OK, yes.

I've not heard of issues relating to fish from aluminum oxide. It is likely fine.


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Unread 11/04/2014, 09:34 AM   #106
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But as a final comment, you are confounding thermodynamic data with kinetic comments (the days comment).
I'm not sure how. Kinetics always wins over thermodynamics when talking about real life. If something happens, but the half-life is 10,000 years, does it happen?

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You certainly can use the Al(OH)3 curve for thermodynamic purposes. The dehydrated Al(OH)3 forms (as phosguard is) will have a more stable crystal, so has a lower equilibrium solubility at every pH, but the pH effects must be exactly the same since all of the forms in solution are identical.
Al(OH)3 and Al2O3 do not interconvert without a redox source (often protons, as detailed in the paper you found). You cannot simply hydrate Al2O3 and make Al(OH3).

The unit cell (a single molecule) of Al2CO3 exists as:

O=Al–O–Al=O

Meanwhile, aluminum (III) hydroxide is:

Al(3+) + 3 (OH-)

You need a redox source. That's why it can happen (to a very small extent at pH 4). But we're talking about pH 8.



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Unread 11/04/2014, 09:47 AM   #107
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First, let's admit that neither you nor I has any actual data (of our own) to back up the conversion of Al2O3 into Al(OH)3 at pH8. Right? Good. Now, let's see what the literature says (not much):

1) It can happen at pH 4. If you supersaturate a solution of pH 4 water, you'll get about 30 ppm Al(OH)3.

2) It can happen at high temperatures (like 300 degC). Here is one example: http://csmb.ornl.gov/~webworks/cppr/...res/120198.pdf

3) Note that Figure 1 of the paper above has a pH plot vs soluble Al(III) for bohemite (aluminum oxide hydroxate). Bohemite is "in between" alumina and aluminum hydroxide. In that plot, maximal solubility is at pH 4 and at pH 8 the solubility is lessened by about 3.5 log units.

** Here is the answer using what's in the literature: If you use the bohemite plot and the data in publication 1, at pH 8 there should be no more than 0.01 ppm Al(III) species in a fully equilibrated sample of water saturated with Al2O3.

I'm ignoring the anecdotes and I'm providing real data from the literature.


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Unread 11/04/2014, 09:57 AM   #108
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I'm not sure how. Kinetics always wins over thermodynamics when talking about real life. If something happens, but the half-life is 10,000 years, does it happen?
First of all, the mechanism you propose for dissolution at pH 4 is clearly not the mechanism that happens at higher pH (say, pH 14) where it dissolves fairly readily, forming Al(OH)4-. So without any kinetic data for dissolution rates at pH 8 (or even pH 4 that I know of), I cannot see how you can even guess what it might be, just because you know the mechanism at pH 4. The mechanism at high pH is probably hydroxide binding to exposed aluminum at the surface, releasing Al(OH)4-, but I'm just speculating that mechanism.

I'll note that the paper posted in this thread says nothing about the rate of dissolution at any pH, except that at pH 4 is complete after 15 days. Maybe it is complete in 15 minutes. There's just no data there on shorter times.

The surface of Al2O3 is already hydrated in water. I'm not talking about a giant single crystal. Phosguard will have all sorts of exposed atoms at edges and defects that are easily hydrated and probably much more rapidly dissolved.

Note that in this same paper, they took the active step to remove the easily dissolved aluminum before even beginning their experiment. Perhaps that stuff is what dissolves first from Phosguard:

"All mineral samples were reacted with 0.1 M HCl (1:1 solid:acid) for 14 days to minimize the effect of reactive surface material."


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Unread 11/04/2014, 10:00 AM   #109
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Originally Posted by Randy Holmes-Farley View Post
First of all, the mechanism you propose for dissolution at pH 4 is clearly not the mechanism that happens at higher pH (say, pH 14) where it dissolves fairly readily, forming Al(OH)4-. So without any kinetic data for dissolution rates at pH 8 (or even pH 4 that I know of), I cannot see how you can even guess what it might be, just because you know the mechanism at pH 4. The mechanism at high pH is probably hydroxide binding to exposed aluminum at the surface, releasing Al(OH)4-, but I'm just speculating that mechanism.
Both mechanisms are well known and not proposed by me. Here is the high pH mechanism that requires free hydroxide:

Al2O3 + 6 NaOH + 3 H2O → 2 Na3Al(OH)6

Again, it's not simply dissolution of ions.


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Unread 11/04/2014, 10:07 AM   #110
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Don't let this comment derail your debate, but I just want to say that I'm really enjoying both of your comments. Very enlightening.

But since shermanator has proposed conducting an experiment (on his dime, no less), I'd really like to hear you both work together to design a methodology that would solve this debate. I, like a number of others, use alumina readily - for filtration, phosphate removal, and like I mentioned previously, it's used in pump impellers/shafts, air stones, etc. It would be very valuable to the hobby collectively if we answered this question a bit more definitively.


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Unread 11/04/2014, 10:18 AM   #111
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But since shermanator has proposed conducting an experiment (on his dime, no less), I'd really like to hear you both work together to design a methodology that would solve this debate.
I've been looking for an appropriate assay and it's going to be tough given the low detection level we are talking about (ideally 0.1 ppm resolution).

I can concentrate the sample (via lyophilization) to concentrate the Al(III), but would need to do proper controls to make sure a known concentration of Al(III) doesn't fall out of solution.

Right now, I'm leaning toward using 8-hydroxy-quinoline. My lab has used it to detect other oxidation state III metals and it works well (it's a ligand that can be observed spectrophotometrically). But the detection limit is closer to 5-10 ppm.

If (and only if) Randy and I agree on the protocol, I'll have a graduate student do it and I won't be involved at all. And I'll blind the samples. But as I said earlier, I don't want to do this if the results won't be taken seriously by the authorities of the field (Randy). Is Advanced Aquarist peer reviewed (by scientists)? If so, I'd be willing to submit an article on this.

--

I'm hopping on a plane soon, so no responses from me for a while. =)


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Unread 11/04/2014, 10:33 AM   #112
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Quote:
Originally Posted by shermanator View Post
Both mechanisms are well known and not proposed by me. Here is the high pH mechanism that requires free hydroxide:

Al2O3 + 6 NaOH + 3 H2O → 2 Na3Al(OH)6

Again, it's not simply dissolution of ions.
I said I thought it was attack of hydroxide.

But don't try to convince me it takes six simultaneous hydroxide ions to release a single surface aluminum ion that is already hydrated. It likely only takes a single one.

But I agree, neither of us has any kinetic data at pH 8.2, especially not in seawater, unless I count my own experiments and accept the hypothesis that the aluminum is dissolved.


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Unread 11/04/2014, 10:43 AM   #113
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Oh bugger... I did the Triton test (Randy knows) and had really high Al. Because I had no other sources of Al (Aside from the potential coming from the Ceramic Block, by Marine Pure) I wanted to do a not too scientific test, and simply remove it from the sump.. while relying on water changes only to see if it drops.

Problem is, I also installed my GFO reactor to address my slightly higher Phosphate result from the test.. now I can't say for sure if the GFO will interfere will the Al removal, as opposed to just water changes.

I would post the high amount of details of my tank (I did this in another forum) but don't want to link it and then get in trouble.


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Unread 11/04/2014, 11:15 AM   #114
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Oh bugger... I did the Triton test (Randy knows) and had really high Al. Because I had no other sources of Al (Aside from the potential coming from the Ceramic Block, by Marine Pure) I wanted to do a not too scientific test, and simply remove it from the sump.. while relying on water changes only to see if it drops.

Problem is, I also installed my GFO reactor to address my slightly higher Phosphate result from the test.. now I can't say for sure if the GFO will interfere will the Al removal, as opposed to just water changes.
(
Well, if your aluminum doesn't decline, then we don't have any idea what we are talking about.


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Unread 11/04/2014, 11:29 AM   #115
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Tag along I was thinking of adding some MarinePure Ceramic Biomedia 1 1/2” Spheres to the second chamber in a media bag in my 24G JBJ nano reef to add some biological filtration


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Unread 11/04/2014, 11:52 AM   #116
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FWIW, I just got my Triton results a few minutes ago. No elevated aluminum for me, which is not surprising since I use GFO and no aluminum media of any sort.


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Unread 11/04/2014, 12:47 PM   #117
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If (and only if) Randy and I agree on the protocol, I'll have a graduate student do it and I won't be involved at all. And I'll blind the samples. But as I said earlier, I don't want to do this if the results won't be taken seriously by the authorities of the field (Randy). Is Advanced Aquarist peer reviewed (by scientists)? If so, I'd be willing to submit an article on this.
Please know that even if Randy is unwilling (which I hope his indifference to your proposal is a sign of him thinking, not ignoring ), I know many hobbyists would find great value in your findings.

Even if alumina products yield some levels of detectable aluminum beyond small particulates, it would be quite useful to know if we're talking about truly soluble aluminum that could prove toxic to our marine life or something more innocuous. MarinePure, for instance, is some pretty cool stuff as we talk about its physical properties and that application in aquaria. I'd hate to eliminate a whole subset of products and materials that could prove very beneficial for our hobby just because of anecdotal evidence.

Randy (in addition to the above plea), what levels of toxicity would we expect to see simply from the addition of MarinePure media? Unlike Phosguard, which would continue to be reintroduced as old material became spent, these blocks are a one-time introduction to our tanks. Electrobe's Triton test showed ~0.22 ppm of Al. If we accept that anything filtered through a 0.45 µm filter is soluble Al, which in your Phosguard experiments showed filtered levels approximately 1/6th of the unfiltered samples, we get something like 0.035 ppm, which is well beneath any levels of toxicity cited in your experiment. If the blocks were leeching, would that number jump considerably over time to cause eventual animal death?


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Unread 11/04/2014, 01:01 PM   #118
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I've been looking for an appropriate assay and it's going to be tough given the low detection level we are talking about (ideally 0.1 ppm resolution).

I can concentrate the sample (via lyophilization) to concentrate the Al(III), but would need to do proper controls to make sure a known concentration of Al(III) doesn't fall out of solution.

Right now, I'm leaning toward using 8-hydroxy-quinoline. My lab has used it to detect other oxidation state III metals and it works well (it's a ligand that can be observed spectrophotometrically). But the detection limit is closer to 5-10 ppm.

These would be my concerns, some of which may be explained away but others might have to be experimentally tested.

1. The sample should be seawater. Concentration for testing will need to be at least 20x to reach the levels needed. At that concentration, lots of compounds are precipitating from seawater. Aluminum may precipitate along with them, maybe even if attached to a chelator, and the chelator may bind to some of the solid surfaces.

2. Will the chelator bind all of the aluminum, even if already chelated by the random organics in seawater? Is it known to bind aluminum at all in seawater, where aluminum normally is complexed to multiple OH- ions?

3. Will the chelator potentially strip aluminum out of colloid surfaces? That is a way I proposed that chelating organics in seawater might increase the release of iron from GFO. If it does, it might blur the line between dissolved and particulate aluminum.


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Unread 11/04/2014, 01:09 PM   #119
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Originally Posted by Fade2White12 View Post
Randy (in addition to the above plea), what levels of toxicity would we expect to see simply from the addition of MarinePure media? Unlike Phosguard, which would continue to be reintroduced as old material became spent, these blocks are a one-time introduction to our tanks. Electrobe's Triton test showed ~0.22 ppm of Al. If we accept that anything filtered through a 0.45 µm filter is soluble Al, which in your Phosguard experiments showed filtered levels approximately 1/6th of the unfiltered samples, we get something like 0.035 ppm, which is well beneath any levels of toxicity cited in your experiment. If the blocks were leeching, would that number jump considerably over time to cause eventual animal death?
I agree the fact that it sits there and is unchanging may help. Moreover, the released aluminum may have time to become chelated to organics to a greater extent if added slowly, and so that may mitigate the toxicity greatly if it is not added at once.

However, that ratio only applied to unrinsed Phosguard (IIRC). In the rinsed Phosguard tests, nearly all of it passed through the 0.45 micron filter.


In the redo of the results at Seachem's request, I got:

Raw IO : no detectable aluminum (<0.05 ppm)
Phosguard water (unfiltered) 0.41 ppm
Phosguard water (filtered) 0.42 ppm

In the original, I got:

Rinsed Phosguard:
Water Sample Exposure Time Filtration Aluminum Concentration (ppm)
Aquarium Water none ................none ...............≤ 0.05
Aquarium Water 2 weeks............. none ...................0.25
Aquarium Water 2 weeks............ 0.45 μm................0.16

and

Unrinsed Phosguard:
Water Sample Exposure Time Filtration Aluminum Concentration (ppm)
Aquarium Water none.............. none.............. ≤ 0.05
Aquarium Water 1 week............... none.......... 0.37
Aquarium Water 1 week ...........0.45 μm .............0.06
Aquarium Water 5 weeks ..........none........................0.71
Aquarium Water 5 weeks ............0.45 μm ................0.12
Instant Ocean none ....................none.................. ≤ 0.05
Instant Ocean 1 week...............none.......................1.11
Instant Ocean 1 week ............0.45 μm........................ 0.13


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Unread 11/04/2014, 01:59 PM   #120
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But don't try to convince me it takes six simultaneous hydroxide ions to release a single surface aluminum ion that is already hydrated. It likely only takes a single one.
I'm on a plane and still cannot stay away from this thread. Ha.

Anyhow, a single hydroxide addition to alumina would give you boehmite (a crystalline, insoluble material).


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Unread 11/04/2014, 02:01 PM   #121
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These would be my concerns, some of which may be explained away but others might have to be experimentally tested.

1. The sample should be seawater. Concentration for testing will need to be at least 20x to reach the levels needed. At that concentration, lots of compounds are precipitating from seawater. Aluminum may precipitate along with them, maybe even if attached to a chelator, and the chelator may bind to some of the solid surfaces.

2. Will the chelator bind all of the aluminum, even if already chelated by the random organics in seawater? Is it known to bind aluminum at all in seawater, where aluminum normally is complexed to multiple OH- ions?

3. Will the chelator potentially strip aluminum out of colloid surfaces? That is a way I proposed that chelating organics in seawater might increase the release of iron from GFO. If it does, it might blur the line between dissolved and particulate aluminum.
All valid issues. I think a standard curve is the first course of action with known amounts of Al(III). That would address 1) and 2) above.

3) could happen and would be in your favor.


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Unread 11/04/2014, 02:06 PM   #122
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But I agree, neither of us has any kinetic data at pH 8.2, especially not in seawater, unless I count my own experiments and accept the hypothesis that the aluminum is dissolved.
If you had at least shown there was no change going from 0.45 um to 0.2 um filtration, you'd give you hypothesis some credence. But (and this is a fact): alumina (al2o3) has particle sizes < .45 um.

Here's some alumina that is 50 nm (10x below the size of your filter cutoff): http://www.sigmaaldrich.com/catalog/...g=en&region=US If you put this stuff in water and find aluminum in an ICP, do you really honestly believe it's accurate to call it ionic Al(III)?



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Unread 11/04/2014, 02:23 PM   #123
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I'm on a plane and still cannot stay away from this thread. Ha.

Anyhow, a single hydroxide addition to alumina would give you boehmite (a crystalline, insoluble material).
Not to every aluminum ion. Just to the one at the edge of the crystal that already is hydrated with two OH groups. It's not bare aluminum ions at the surface, nor "oxide" ions.

One by one we dissolve them away.


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Unread 11/04/2014, 02:26 PM   #124
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If you had at least shown there was no change going from 0.45 um to 0.2 um filtration, you'd give you hypothesis some credence. But (and this is a fact): alumina (al2o3) has particle sizes < .45 um.

Here's some alumina that is 50 nm (10x below the size of your filter cutoff): http://www.sigmaaldrich.com/catalog/...g=en&region=US If you put this stuff in water and find aluminum in an ICP, do you really honestly believe it's accurate to call it ionic Al(III)?
Nope, and I don't think I did call them that, did I?

Only the ones that hydrate and dissolve into the water would be called individual ions of Al(OH)3 and Al(OH)4-.


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Unread 11/04/2014, 02:30 PM   #125
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Nope, and I don't think I did call them that, did I?

Only the ones that hydrate and dissolve into the water would be called individual ions of Al(OH)3 and Al(OH)4-.
Your definition of dissolve is something not filtered at 0.45 um (see your article and in this thread). I disagree with that. If you put alumina nanoparticles in water they will pass through a larger filter pore. In your method, you'd see 50 nm alumina in your ICP. If you disagree with that, I'm lost and give up.

Alumina will degrade with a variety of sizes. It's why filtering has an effect at all. But the size distribution of alumina certainly includes particles smaller than your .45 um filter.


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