Bedlasky
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CrPO4 and FePO4 ion exchange
Hi.
I read that CrPO4 and FePO4 can be used as ion exchange resins. Look at this, it is quite interesting:
https://cdnsciencepub.com/doi/pdf/10.1139/v76-270
https://en.m.wikipedia.org/wiki/Chromium(III)_phosphate
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Maurice VD 37
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So what is your question ?
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Bedlasky
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I don't have question, I just share these links with others. Maybe I will try to make FePO4 resin, but I don't have time now.
[Edited on 1-12-2020 by Bedlasky]
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Bedlasky
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I plan to make ferric phosphate according to article above. I'll make two batches: First from 1:2 0,1M Fe(NO3)3:0,1M NH4H2PO4, second from 1:2 0,1M
NH4Fe(SO4)2.12H2O:0,1M H3PO4. First should have highest ion exchange capacity. Second will be just attempt if nitrate can be replaced by more common
sulfate.
I have a question. In the paper say: Ferric phosphate was precipitated by adding phosphoric acid or ammonium dihydrogen phosphate to the solution of
ferric nitrate with constant stirring under the conditions given in Table 1. The required pH of the final product was adjusted by adding either
hydrochloric acid or sodium hydroxide solution.
I think that precipitation pH is that both solutions, which are mixed, have the same pH, precipitate is formed at the same pH. But this looks like
they adjust pH after the precipitation to required value. So I am not sure what to do.
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Bezaleel
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Quote: Originally posted by Bedlasky  | I plan to make ferric phosphate according to article above. I'll make two batches: First from 1:2 0,1M Fe(NO3)3:0,1M NH4H2PO4, second from 1:2 0,1M
NH4Fe(SO4)2.12H2O:0,1M H3PO4. First should have highest ion exchange capacity. Second will be just attempt if nitrate can be replaced by more common
sulfate.
I have a question. In the paper say: Ferric phosphate was precipitated by adding phosphoric acid or ammonium dihydrogen phosphate to the solution of
ferric nitrate with constant stirring under the conditions given in Table 1. The required pH of the final product was adjusted by adding either
hydrochloric acid or sodium hydroxide solution.
I think that precipitation pH is that both solutions, which are mixed, have the same pH, precipitate is formed at the same pH. But this looks like
they adjust pH after the precipitation to required value. So I am not sure what to do. |
My guess is that they add NaOH, because iron(III)phosphate is soluble in acidic solutions. I tried this last week, and adding H3PO4 to FeCl3 solution
does not give much precipitate, only a very tiny bit.
Ferric nitrate is also a peculiar choice as a starting point, because it is not very soluble in acidic environment.
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Bedlasky
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Bazaleel: Look at the paper. Ferric phosphate is prepared at different pH, each form have different ion exchange capacity, so pH is really important.
So if precipitation pH is 1, ferric phosphate must to be formed at pH 1. After preparation they convert it in to fully protonated form using 1M HNO3
(which have pH = 0). But I am little bit worried about this step. I tried if ferric phosphate withstand such a low pH. So I tried precipitating from
1M HCl and it didn't work. I added NaOH and at cca pH = 2 ferric phosphate start to precipitate. Maybe I add too much NaOH and it can precipitate at
lower pH values, I don't know, this wasn't very accurate measurment, just a quick test tube test.
Ferric nitrate have a low solubility? According to wiki hexahydrate have solubility 150 g/100 ml. This doesn't seem as low solubility. In addition low
pH helps to dissolve ferric salts in general.
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unionised
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| Quote: Originally posted by Bezaleel |
Ferric nitrate is also a peculiar choice as a starting point, because it is not very soluble in acidic environment. |
Ferric nitrate is pretty soluble as pointed out.
The reason they use it is that the nitrate ion doesn't form complexes readily whereas sulphate and, particularly, chloride do.
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