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11/04/2014, 03:43 PM | #126 | |
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It is the standard in oceanography for such things as particulate organic matter (POM) vs dissolved organic matter (DOM): http://www.terrapub.co.jp/journals/J...2/58020265.pdf "The first difficulty that one must confront in any definition of POM is to define the term “particulate”. Usually it has an operational definition as any material that does not pass through a given filter—usually a 0.5 µm filter. " However, I do recognize the difference between aluminum ions as individuals, and aluminum ions packed into a colloid with other aluminum ions. I have not claimed that the aluminum released is individual ions, but I think that a reasonable portion of it is likely to be. The same is used for POC (particulate organic carbon), DOC, POP (particulate organic phosphorus), DOP, etc. Maybe I should call it "Dissolved aluminum matter" to be consistent, DAM.
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11/04/2014, 05:45 PM | #127 | |
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Using what little is available via literature, I've shown (post #107) that the levels you found by ICP are extremely unlikely to be ionic Al(III). Now I'm thinking it's time for me to stop debating this topic (I have to make some slides for a talk tomorrow anyhow). It's experiment time! (well, next week I'll find a grad student to "volunteer" and get them going).* * I'm still uncertain the methodology I have proposed will have sufficient S/N. We should know in two weeks if we can generate a standard curve for Al(III) in saltwater. And Randy, I've enjoyed the debate. I'm an organic/medicinal chemist, so this is a bit afield. That said, it's been a good refresher of general and inorganic chemistry. Since I know who you are (and your credentials), if you want to know who I am, PM me. I've hugely enjoyed your works and contributions. I disagree with you here, but hey, the beauty of science is that we can figure out the correct answer. |
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11/04/2014, 06:16 PM | #128 |
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This is the most enjoyable and interesting discussion I've read in some time on Reef Central. Rock on chemists!! Let's get to the bottom of the aluminum in reef tanks issue!
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11/04/2014, 06:21 PM | #129 | |
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~Phil Current Tank Info: 205 gallon in-wall, SPS dominated |
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11/04/2014, 06:38 PM | #130 |
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Agreed this thread is like reading the large tank threads :-). Any chance others can be tested as well? Like Seachem Matrix or other ceramic based media? I would be happy to supply some matrix :-)
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11/04/2014, 06:51 PM | #131 | |
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I don't have any Matrix, but do have Seachem DeNitrate. I think they are the same composition (?) but DeNitrate is smaller pieces. Let's see what comes of the assay... |
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11/04/2014, 07:18 PM | #132 | ||
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11/05/2014, 06:43 AM | #133 | |
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11/05/2014, 06:53 AM | #134 | |
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11/05/2014, 07:01 AM | #135 | |
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FWIW, I expect AA will come up with some competent reviewers, but if not, I'm sure there are some expert reef chemists such as Chris Jury or Craig Bingman who would review it if we asked them. A couple of other suggestions: 1. The standard should circulate in the seawater for as long as the media does (which should be a substantial period, such as a week) in case free aluminum ions are binding to bacteria or other particulates that would be filtered out (or at least that should be an arm of the study). 2. While I think the nature of the released aluminum is an intellectually interesting issue, and I'm eager to see what form it takes, I would not, a priori, agree with your assertion that if it is not independent aluminum ions, it cannot be toxic. Unless someone has studied the impact of nanoparticles of aluminum oxide on corals and such, that is just speculation. It might be right, but it isn't established. Such particles will quickly be coated with organics and look like food. Ingestion of them may give some organisms indigestion.
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11/05/2014, 07:04 AM | #136 | |
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Since I think it likely that some individual ions are released, I would have been inclined to word it that way anyway, but I agree it is definitely not proven.
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11/05/2014, 08:06 AM | #137 |
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regarding the solubility curves and the discussion of the toxicity of Alumina and all that - did we remember to mention that Triton's going to process the sample in 1 M HN03? You've taken your seawater sample at pH ~ 8.0 and dropped it down to ~4.0 (just guesses on the pH by the way).
ICP doesn't tell us the nature of the constituents - only the total constituents. So it could indeed be non-soluable, non-toxic alumina floating around our aquariums and the particulate is annoying the leathers the same way GFO particulate can annoy SPS or carbon particulate can annoy tangs. The source of aluminum via the ICP test could be dust blowing in the window (clays and dirt and such are very high in Al/Mg/Si). |
11/05/2014, 08:28 AM | #138 | |
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If one really wanted to "close the loop" on this, it would require some biology experiments with colloidal aluminum/organoaluminum compounds. |
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11/05/2014, 08:48 AM | #139 | |
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11/05/2014, 08:51 AM | #140 | |
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Even if they are free ions, chelation by organics can greatly reduce that toxicity.
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11/05/2014, 10:00 AM | #141 |
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Here's a paper that shows the kinetics and dissolution of fine particles of alumina over the pH range of 3 to 11. I could only preview it for 5 minutes without buying it, and could not find the data I wanted in that time, but we may not need to do the experiment if someone has access to this paper and can see the equilibrium solubilities in the pH 7-9 range for us.
It also gives a method for detecting the dissolved aluminum, although I do not know its lower limit of detection. Dissolution kinetics of nanodispersed γ-alumina in aqueous solution at different pH: Unusual kinetic size effect and formation of a new phase http://www.sciencedirect.com/science...21979706007302
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11/05/2014, 10:28 AM | #142 |
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Here's another paper that measures the dissolution of alumina as a function of pH (they use ICP to match their modelling of released individual ions of aluminum.
They didn't quote a value for the data around pH 8, but looking at the data point on the graph (Figures 7 and 8), it looks to me to be about 0.00005 M, or 1.4 ppm (or perhaps a tad lower), although it might easily be a factor of 2 higher or lower since I can't be sure they put the data point exactly on the actual value. Still that is higher than I measured in my experiment, and suggests the possibility the the aluminum is truly dissolved forms of Al(OH)3 and Al(OH)4-. http://www.academia.edu/679100/Inter...tion_of_solid_
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11/05/2014, 10:48 AM | #143 | |
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Click me! Last edited by Fade2White12; 11/05/2014 at 10:59 AM. |
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11/05/2014, 11:07 AM | #144 |
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Thanks.
So sample A09001 (pH 9 dissolution of the alumina; Figure 1 and Table 5) shows an equilibrium concentration of free aluminum of 7.05 x 10^-6 M, which corresponds to 0.2 ppm (note the data quoted in Table 5 (0.2 ppm) seems higher than Figure 1 (0.1 ppm), for reasons I cannot understand) I'm satisfied.
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Randy Holmes-Farley Current Tank Info: 120 mixed reef Last edited by Randy Holmes-Farley; 11/05/2014 at 11:24 AM. |
11/05/2014, 11:09 AM | #145 |
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So I am Lost lol Marine pure ceramic biomedia Good product or no LOL
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11/05/2014, 11:11 AM | #146 | |
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EDIT: I see someone else posted it! Nevermind! |
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11/05/2014, 11:18 AM | #147 |
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FWIW, that A09001 sample is an especially interesting one (at least to a chemist), as it reaches a much higher concentration (1.9 ppm) transiently and then begins to reprecipitate in a different form (bayerite in addition to gamma-alumina) before reaching equilibrium at 0.2 ppm. That didn't happen at most other pH values.
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11/05/2014, 11:20 AM | #148 | |
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That's not so easily answered as the chemistry involved. For me personally, I wouldn't use products that released aluminum, but if you do not have any of the tell tale signs of aluminum issues (such as closed leathers) it is not likely an issue and if you already have it in place, I might not remove it.
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11/05/2014, 11:20 AM | #149 | |
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This space for rent... Current Tank Info: 36x36x16 A.G.E. tank. Lighting: ATI Straton. Circulation: 2x Vortech MP40wQd's. Skimmer: Red Sea 300. Controller: Neptune Apex. Doser: Neptune Dos. |
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11/05/2014, 12:18 PM | #150 |
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Reminds me of Ebola fear (although not funny). Some people start to have fear of Marine Pure stuffs.
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