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11/03/2014, 02:50 PM | #76 | |
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That was their "test" tank. It happen so often that it was not a one time thing.
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11/03/2014, 02:51 PM | #77 | |
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The only asterisk one would have to add to the above supposition is that the rate of dissolution from the solid has to be reasonably non-rate limited. |
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11/03/2014, 02:55 PM | #78 |
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I know that Phosguard has been of great contention between Randy and Seachem over the years. What are the differences in the more recent study by Batten and Lafayette vs. Randy that would lead to such different conclusions? Seachem continues to hold that alumina is not soluble in reef tanks.
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11/03/2014, 02:58 PM | #79 | |
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And to be clear... I'm not saying that your measurements are wrong. I'm saying that the soluble filtrate you obtained is almost certainly Al2O3 and not ionic Al(III). I make a big distinction from something being "in solution" and something ionic. I'll tell you what... I have to leave in a few minutes to get my kids -- and I'm giving a couple seminars out of town the remainder of this week, but here is what I will do... I'll buy some Phosguard (and/or MarinePure Media, which I do have) and dissolve it in 18-ohm water. I'll filter it with both 0.45 µm and 0.2 µm syringe filters. I'll buy an Al(III) spectrophotometric test kit (should be silent for Al2O3, even "dissolved" Al2O3) and post the results. I'll make a student do it. It'll take me a few weeks. But let's agree to the methods (and a test kit), if possible. Last edited by shermanator; 11/03/2014 at 03:04 PM. |
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11/03/2014, 02:59 PM | #80 |
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I wish I understood what you two are talking about!
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11/03/2014, 03:00 PM | #81 | |
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But yes, from a thermodynamics point of view, everything is reversible. And from a thermodynamics view, I can walk through a wall, too. |
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11/03/2014, 03:06 PM | #82 | |
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11/03/2014, 03:14 PM | #83 | |
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On the solubility vs pH, yes it goes 10x per pH unit for much of the pH range, but solubility is increasing 10x per pH unit above pH 7, where it reached a minimun for aluminum. I'd just read the article I linked, but if you want to do experiments, go for it!
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Randy Holmes-Farley Current Tank Info: 120 mixed reef Last edited by Randy Holmes-Farley; 11/03/2014 at 03:43 PM. |
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11/03/2014, 03:21 PM | #84 | |
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I addressed it in 2008 and referred to it here, but I do not have the original discussion thred any longer as it is not archived: http://www.reefcentral.com/forums/sh....php?t=1504036 I'll see if I can remember what their problems were, but as I recall, they did not have an adequately low limit of quantitation to detect what I saw as they used a different method.
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11/03/2014, 03:38 PM | #85 |
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In any case, all tox issues aside, since the manufacturer claims this Marine P Ceramic Biomedia contains substantial aluminum oxide, and aluminum oxide is known in the scientific literature to release aluminum to fresh water, I think it is reasonable to conclude that elevated aluminum levels may be coming from this Biopure media.
Folks might argue what form it takes, and what harm it may cause (if any), but the potential for it to possibly be the cause of detectable elevated levels in aquarium tests, IMO, is not really much in doubt.
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11/03/2014, 03:42 PM | #86 | |
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11/03/2014, 03:43 PM | #87 |
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That's a bummer. I bought two blocks of it for an expansion...
Well at least the vidarock didn't raise my tank's aluminum. |
11/03/2014, 03:48 PM | #88 |
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Let me see if I can put it into layman's terms for the rest of us...
This week on Fe(III) Chef ... now entering Labratory Stadium, the challenger, shermanator facing the reigning master, Randy Holmes-Farley. And now to reveal this weeks, secret ingredient [Chairman Kaga whips the covering from the table with a flourish] PHOSGUARD!! [gasps: from the audience at the sheer mountain of phosguard!] Dennis
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11/03/2014, 03:52 PM | #89 |
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My head won't stop spinning
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11/03/2014, 04:17 PM | #90 |
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11/03/2014, 04:22 PM | #91 |
im an addict lol
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Wow
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11/03/2014, 05:07 PM | #92 | |
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The full pH graph is in Pankow, "Aquatic Chemistry Concepts", but for amorphous aluminum hydroxide, not the dehydrated corundum. Still, the shape will be the same, just moved down a bit. At pH 8.2, it shows a bit higher than 10^-4 M (2.7 ppm). At pH 4 is shows about 800 ppm. Since corundum is about 31 fold lower at pH 4, it will also be about that same lower at pH 8.2, so about 2.7/30 ~0.1 ppm. I measured 0.4 ppm. IMO, that is close enough to suggest that what I saw is soluble aluminum from aluminum oxide. I'll try to scan and post it.
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11/03/2014, 05:37 PM | #93 | |
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If you can post that plot, would be great. We should be able to calculate this via k-sp. I'll work on it after the kids are in bed. |
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11/03/2014, 06:19 PM | #94 |
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Here's the curve for aluminum solubility as a function of pH in fresh water.
It is for aluminum hydroxide, so the data for aluminum oxide will be the same curve, but moved straight down becasue it is a more stable crystal form. That said, I don't think we know what crystal forms Phorguard shows on its hydrated surface, so it would likely be between amorphous corundum and amorphous aluminum hydroxide. I believe it is correct to cross over the data at pH 4 (where we have data for both forms), as I mentioned above, giving solubility for corundum around 0.1 ppm in fresh water at pH 8.2
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11/03/2014, 07:16 PM | #95 |
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Randy, any chance you might know if seachems matrix bio media might have the same issue as I have used it in both reef and discus tanks.
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11/03/2014, 07:49 PM | #96 |
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Okay, I'm back. A couple notes after reading the Peryea paper:
1) All their data is at pH 4, and over a long time scale (15–45 days). 2) Their mechanism for solubilization is a protic solubilization and requires 6 protons per Al2O3 (equation 1) to make 2 Al(III) 3) At pH 4 and 15 days, they measure 9x10^-4 M Al(III) or ~30 ppm Al(III) 4) At pH 8, there are 10^4 fewer (free) protons compared to pH 4. If you ballpark 3) and 4) above, at pH 8, there isn't going to be anywhere near 0.1 ppm Al(III) in solution. I'm not sure you can use the aluminum hydroxide curves. It's a very different process. With aluminum hydroxide you are looking at dissolution of ions. With Al2O3 (alumina), there is a chemical reaction that is occurring and requiring protons (or hydroxide). But, this is getting outside my chemistry area of expertise so I might be wrong about the applicability of that curve. I really couldn't find much on the solubility of alumina. I found some papers saying they got micrograms to dissolve, but that was at 800 degC and high pressure. I'll just say it's not very soluble. Maybe this is getting too academic? I'm still willing to test for soluble Al(III) as I proposed earlier, but I want you to help design the experiment so that you will accept the results. No point in spending time and money if neither of us will be convinced (or the experiments are not designed in a way to tell us anything informative). Last edited by shermanator; 11/03/2014 at 08:33 PM. |
11/03/2014, 07:50 PM | #97 |
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11/03/2014, 08:44 PM | #98 | ||
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I'm all for science and adding technology to everyday life. But, as evidenced in our debate, I fail to see how ICP (Triton) tells us anything useful about Al levels. It causes panic and concern when no one (including both you and I) knows if the elevated atomic Al is concerning (aluminum hydrates) or inert (Al2O3). |
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11/04/2014, 05:02 AM | #99 | |
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But as a final comment, you are confounding thermodynamic data with kinetic comments (the days comment). Phosguard is designed to be a very high surface area material. I don't know exactly what the paper used, but I expect it was not like Phosguard, and so will dissolve more slowly than Phosguard. I see no reason to not think it reaches equilibrium faster. 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.
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11/04/2014, 05:06 AM | #100 | |
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I don't really know much about fluorescence of aluminum, or if different forms that might exist (organic chelated, Al(OH)3, Al(OH)4-, Al(OH)3CO3--, etc. will have different emissions, or all overlap and be countable, and how you distinguish very fine particles from soluble aluminum, or even what that means if they are small aggregates of a few aluminum atoms.
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