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vibbzlab
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[*] posted on 14-12-2019 at 03:58
Purify ferrous sulfate


I tried to make ferrous sulfate by adding Sulfuric acid to scrap stainless steel and I got green crystals from that. But seeing the colour of it I think there is good amount of contaminants in it probably chromium. Is there any way to purify it

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[*] posted on 14-12-2019 at 04:21


Pure FeSO4 looks similiary like your crystals. Look on crystalgrowing. But if you use staniless steel as a source of iron, it contain some Ni and Cr salts. Cr salts can be removed by just dissolving crystals and addition of excess of NaOH. Fe and Ni precipitates and Cr stay in solution. Ni can be dissolved by addition of ammonia. Then filtered your Fe precipitate, dissolve it in sulfuric acid, add few iron nails and boil it for few minutes. Iron nails reduce any Fe(III) in solution in to Fe(II).
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vibbzlab
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[*] posted on 14-12-2019 at 06:33


Thanks for that .So I will dissolve it in minimum amount of water to make a solution and then add concentrated sodium hydroxide in excess right?
Then I would add ammonia into it? Or should I filter the precipitate first then add ammonia? After that I should filter the ppt and then add Sulfuric acid with iron nails and boil that for few minutes and recrystallise right





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[*] posted on 14-12-2019 at 06:52


I would start by taking a little of it, rinsing it and then dissolving it in water in a test tube.
Then add excess ammonia, and filtering it.
Cr and Ni will dissolve as amine complexes and pass through the filter.
If the filtrate is colourless then there's not enough Ni or Cr to worry about.
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[*] posted on 14-12-2019 at 09:22


By excess ammonia how much do you mean. Can you tell




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[*] posted on 14-12-2019 at 09:35


Until no more precipitate forms when you add more, the solution stops changing colour (apart from getting a little paler because it becomes more dilute) and the mixture smells strongly of ammonia.
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[*] posted on 14-12-2019 at 10:08


i'm really new to the forum, can someone explain to me why recrystallizing it won't work? Only thing I can think of is that Fe, Ni, and Cr similar enough that they can replace each other in the crystal structure so they all crystallize out together but i don't know if that's right. Thanks.
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[*] posted on 14-12-2019 at 12:02


Because this is much easier method of separation. Another benefit is that you have higher yield because losses from precipitation are much lower than losses from multiple recrystallizations.
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[*] posted on 14-12-2019 at 13:04


Cr(III) is not likely to be incorporated into the FeSO4- the charge is "wrong" so it won't fit properly.
But Ni (and Cu and Mn + Zn) if they are there will co crystallise.
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[*] posted on 14-12-2019 at 16:34


I think adding ammonia and refiltering the solution then adding Sulfuric acid again isn't that hard




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[*] posted on 14-12-2019 at 16:54


Just a general comment to be taken with a grain of salt (NaCl?) by anyone who reads it: many (not all) questions about separating inorganic species could be answered by referring to qualitative analytical chemistry and/or qualitative analytical chemistry textbooks.
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[*] posted on 24-12-2019 at 04:10


I have decided to convert all that stainless steel sulfate solution into ferrous oxalate thereby I can get pure iron as we can precipitate out that compound with oxalic acid




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[*] posted on 24-12-2019 at 06:30


I would honestly simply recrystallize your ferrous sulfate from boiling water when you have a significant quantity of the crude product. Chromium(III) compounds form extremely hygroscopic coordination complexes containing water ligands after being heated above 40C, and they're very slow to exchange ligands thereafter. Simply re-crystallizing and then washing your crystals with ice water should remove chromium and nickel sulfates, the latter of which is far more soluble than FeSO4.
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[*] posted on 24-12-2019 at 10:26


As you and others said, you can remove chromium by recrystallising (just keep solution acidic to prevent Cr(OH)3 from forming), but is won't remove nickel, it forms shared crystals with FeSO4. Starting over with scrap cast iron or steel wool would be more cost effective than removing nickel.
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[*] posted on 24-12-2019 at 12:15


Quote: Originally posted by vibbzlab  
I have decided to convert all that stainless steel sulfate solution into ferrous oxalate thereby I can get pure iron as we can precipitate out that compound with oxalic acid


Nickel oxalate is insoluble as well.
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[*] posted on 24-12-2019 at 12:49


Quote: Originally posted by Bedlasky  
Quote: Originally posted by vibbzlab  
I have decided to convert all that stainless steel sulfate solution into ferrous oxalate thereby I can get pure iron as we can precipitate out that compound with oxalic acid


Nickel oxalate is insoluble as well.


Could go the other way and complex out the iron with some H2O2... sodium triferrooxalate is also a pretty crystal to grow.




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[*] posted on 25-12-2019 at 12:05


Maybe I'm exposing a blind spot in my inorganic chemistry knowledge, but why is everyone suggesting that nickel will co-crystallize with iron when nickel(II) sulfate is approximately 4 times more soluble in room-temperature water and the most common hydrates have vastly different crystal structures?
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[*] posted on 13-1-2020 at 09:17


I have found that it's really contaminated with chromium. I got several ideas to seperate it. People told me to use alcohol as a medium because chromium sulfate is easily soluble in methanol. And ferrous sulfate seperates which can just crystalise out.
I also tried to seperate out iron oxalate crystals by adding a concentrated solution of oxalic acid into it.
Here is the preparation video
https://youtu.be/hQ3YwDnYdYk

sulfate precipitate out as yellow colored solution.





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[*] posted on 15-1-2020 at 10:10


Quote: Originally posted by vibbzlab  
I tried to make ferrous sulfate by adding Sulfuric acid to scrap stainless steel and I got green crystals from that. But seeing the colour of it I think there is good amount of contaminants in it probably chromium. Is there any way to purify it

This is not the color of FeSO4.7H2O. The latter has a fairly pale mint green color, not the strong green color of your material.

Here is a picture of pure ferrous sulfate:

https://woelen.homescience.net/science/chem/compounds/ferrou...



[Edited on 15-1-20 by woelen]




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[*] posted on 15-1-2020 at 16:44


if you need pure FeSO4 then react H2SO4 with Electrical steel https://en.wikipedia.org/wiki/Electrical_steel it a alloy of Fe and Si with often no other impurity's Si won't get dissolved. in Hit can get from old transformer(I and E shaped plates). keep in mind they have thin layer of polymer that have to remove with sand paper.

please don't start arguments over pictures of compounds over the internet as ebay sellers say color may change display to display.




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[*] posted on 22-1-2020 at 05:57


Finally I was able to get iron oxalate from that contaminated stainless steel solution by adding Sulfuric acid into it. I filtered the solution and obtained the precipitate which I dried.i heated it to make the pyrophoric iron and it worked perfectly fine . I have added a picture of ferrous oxalate here.
Here is the preparation video of the compound and the pyrophoric test
https://youtu.be/Yo7Im90rX2s

IMG_20200122_190345_252.jpg - 178kB





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[*] posted on 23-1-2020 at 03:46


If your target was Iron^2 Sulfate why did you decide to use stainless if I may ask?

I needed some for a catalyst for making dioxane, so I used black iron gas pipe (Just carbon steel)

So just filtered out the carbon after I had boiled the solution with excess iron pipe.

Yield was nice pale green iron 2 sulfate.

to the right is Copper Nitrate to contrast the color

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