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11/04/2014, 07:48 AM | #101 |
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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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11/04/2014, 08:05 AM | #102 | |
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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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330g SPS - LED/T5 - EShopp S-300 Skimmer - 4 x Jebao PP20- reefkeeper elite Current Tank Info: 210 gallon mixed reef lps sps |
11/04/2014, 08:27 AM | #104 | |
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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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11/04/2014, 08:28 AM | #105 | |
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I've not heard of issues relating to fish from aluminum oxide. It is likely fine.
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11/04/2014, 09:34 AM | #106 | ||
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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. Last edited by shermanator; 11/04/2014 at 09:51 AM. |
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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. |
11/04/2014, 09:57 AM | #108 | |
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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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11/04/2014, 10:00 AM | #109 | |
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Al2O3 + 6 NaOH + 3 H2O → 2 Na3Al(OH)6 Again, it's not simply dissolution of ions. |
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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. |
11/04/2014, 10:18 AM | #111 | |
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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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11/04/2014, 10:33 AM | #112 | |
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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. 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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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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11/04/2014, 11:15 AM | #114 | |
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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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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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11/04/2014, 12:47 PM | #117 | |
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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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11/04/2014, 01:01 PM | #118 | |
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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.
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11/04/2014, 01:09 PM | #119 | |
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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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11/04/2014, 01:59 PM | #120 | |
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Anyhow, a single hydroxide addition to alumina would give you boehmite (a crystalline, insoluble material). |
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11/04/2014, 02:01 PM | #121 | |
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3) could happen and would be in your favor. |
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11/04/2014, 02:06 PM | #122 | |
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Here's some alumina that is 50 nm (10x below the size of your filter cutoff): http://www.sigmaaldrich.com/catalog/...g=en®ion=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)? Last edited by shermanator; 11/04/2014 at 02:19 PM. |
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11/04/2014, 02:23 PM | #123 | |
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One by one we dissolve them away.
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11/04/2014, 02:26 PM | #124 | |
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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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11/04/2014, 02:30 PM | #125 | |
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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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