Sciencemadness Discussion Board

Unsure how to effectively filter nickle sludge and clean remaining residue from glasswear

alking - 2-2-2017 at 09:31

So I have some nickel aluminum amalgam which I've activated with a base soak. From there I filter and wash it to remove any base. Filtering it is very slow and tedious with a buchner and filter paper. I have a sintered funnel which I'm sure would work better, but I'm concerned that the nickel will clog the frit and I will be unable to get it out effectively ruining my filter.

I would have assumed that I could dissolve it easily enough with a strong mineral acid, but testing some that doesn't actually seem to work at all, I'm unsure why? I have tried hcl, h2so4, and piranha solution. Am I wrong in assuming that this should dissolve? If it doesn't do you have any suggestions on how to better filter it? I can't use celite since I need to actually recover the nickel, not the solution which it is in. If it should be dissolving any idea why it's not? The only idea I have left is to make some nitric acid or aqua regia, but since I don't have any on hand already I'd really like to avoid that extra work if at all possible.

Metacelsus - 2-2-2017 at 10:27

I recently (last night, actually) had this problem after a Raney nickel reduction. I discovered that it was possible to remove most of the nickel using a strong magnet. Then, I used celite to help filter the remaining nickel.

Based on my experience, you might be able to get a lot of the nickel back using a strong magnet.

[Edited on 2-2-2017 by Metacelsus]

Praxichys - 2-2-2017 at 10:55

Nickel metal is pretty resilient and is attacked only very slowly by non-oxidizing acids like sulfuric and hydrochloric. Check this photo out:

http://fphoto.photoshelter.com/image/I0000rNoyMFd5KhQ

This is nickel shot in concentrated HCl after 10 days. Barely anything!

You will be much better off with warm nitric or perchloric acid if you want to get rid if it quickly. You don't necessarily have to prepare the nitric acid. You could always just use a mixture of sulfuric acid and a nitrate salt.

Fulmen - 2-2-2017 at 11:50

Perhaps HCl + H2O2 if nitric or perchloric acid isn't available?

alking - 2-2-2017 at 13:49

Quote: Originally posted by Metacelsus  
I recently (last night, actually) had this problem after a Raney nickel reduction. I discovered that it was possible to remove most of the nickel using a strong magnet. Then, I used celite to help filter the remaining nickel.

Based on my experience, you might be able to get a lot of the nickel back using a strong magnet.

[Edited on 2-2-2017 by Metacelsus]


Do you mean I should activate it and then 'extract' it with a magnet? Then filter the rest through celite and discard w/e is caught in the celite? Or do you mean to filter it through the frit and then 'clean' the frit with a magnet?
Quote: Originally posted by Praxichys  
You could always just use a mixture of sulfuric acid and a nitrate salt.


Good point, that should still clean things well enough.
Quote: Originally posted by Fulmen  
Perhaps HCl + H2O2 if nitric or perchloric acid isn't available?


I tried piranha solution and it didn't touch it, though it's possible it just wasn't strong enough as I didn't add enough H2O2 to make it full strength. I originally tried this on some glassware that had some nickle scaling though and I think because I just added a small amount of H2SO4 that I did add an appropriate amount of H2O2 but I can't remember for sure. I may test it again before using up some of my limited nitrite salts. I should pick up a larger quantity of nitrate or something as it's pretty useful for things like this, but like so many other things it ends up getting pushed down the list.

Σldritch - 3-2-2017 at 08:56

Acidic iron (III) chloride might work but if piranha solution does not do it i doubt ferric chloride will.

http://lanthanumkchemistry.over-blog.com/article-the-dissolv...

[Edited on 3-2-2017 by Σldritch]

alking - 3-2-2017 at 09:44

Awesome, thanks for the link. Perhaps I did not use enough H2O2, I am running low so I might have been over-conservative when making the piranha solution. Strangely that article mentions HCl + H2O2 but makes no mention of piranha solution/H2SO4 + H202 so perhaps HCl + H2O2 is actually more reactive towards Ni.

Melgar - 3-2-2017 at 13:08

Piranha solution doesn't do much to less-reactive metals unless you dilute it. There needs to be enough water to form the hexahydrate so it can go into solution, otherwise it's insoluble in piranha, and so blocks the surface from further attack. Similar to how concentrated nitric acid will barely dissolve silver at all, but dilute acid will eat right through it. Even with the more reactive metals like aluminum, zinc, and magnesium, adding piranha to them is more likely to reduce the sulfuric acid to SO2 or H2S than it is to dissolve it in the manner of a typical acid, or catalyze the decomposition of the H2O2.

So I guess the key point here is, don't use piranha on metals, because it will probably either do little to nothing or generate toxic, foul-smelling fumes. Also, when dissolving metal into a solution, leave enough water without stuff dissolved in it, so that the metal salts will have somewhere to go when they form. Incidentally, I've found these mixtures to work best for dissolving metals:

1) HNO3 + H2O2 (dilute): This mixture is great because the H2O2 will oxidize the NOx fumes back to nitric acid before they can escape the vessel.

2) H2SO4 + H2O2 (dilute): Good for copper, nickel, and most other metals that form soluble sulfate salts.

3) HCl + H2O2 (dilute): The H2O2 has to be added very slowly and carefully at first, and you should monitor the temperature and check for chlorine gas, stopping if there's a sudden increase in either. This one is fairly dangerous, but it's far and away the best way to make copper (ii) chloride via copper metal. More dilute solutions decrease the chance of a thermal runaway.

4) H2SO4 + HNO3 + H2O2 (dilute): You don't really need both oxidizers, and you can just stick with whichever is more available, at least for most metals. The mixture has been known to dissolve some metals particularly fast though, and the H2O2 prevents the evolution of NOx fumes.

5) HCl + HNO3 + H2O2 (dilute): This one decomposes itself, I'm pretty sure, and the evolution of weird acid fumes containing both nitrogen and chlorine probably isn't worth the reduction in NOx emissions.