I have started to use citric acid instead of safety pickle or other
stronger acids, to reduce environmental impact; I felt pleased with
myself for a while, but have been informed now that the acid content
is less of an issue than the quantity of copper being flushed into
the drains when the neutralised pickle is discarded.
As Copper so beautifully plates silver when a student accidentally
puts steel tweezers in the mix, I wonder if there is a way to use
this method of extraction to make the spent pickle more friendly to
the waterways?? Obviously I don’t want to be using my silver for
this job!!
You can use the same cementation process used to extract copper from
acid mine water: just throw in some scrap iron in the form of steel
cans, wire, steel wool, etc. The iron will go into solution while the
copper plates out. Or you can neutralize the solution with baking
soda and the copper will settle out as a solid sludge.
As Copper so beautifully plates silver when a student accidentally
puts steel tweezers in the mix, I wonder if there is a way to use
this method of extraction to make the spent pickle more friendly
to the waterways?? Obviously I don't want to be using my silver for
this job!!
Get a large industrial roll of steel wool to keep the price down and
place a wad of steel wool into the spent pickle. It will turn pink,
remove/drain the steel wool and place in trash bag, repeat using
fresh steel wool until it no longer turns pink. You have now removed
the vast majority of the copper form the solution and the copper
plated steel wool can be sent to a scrap yard for recycling.
This is a very old convo that I think is pretty relevant. Well, it is to me, anyway… and may get some love from the other pickling thread.
Question:
After one removes the copper in solution with the steel wool, and after one has removed the now plated steel wools, is this pickle again suitable for pickling or now is it suitable for neutralizing and discards only?
This is a good question! I would think that after the majority of the cooper is removed it’s safe to neutralize and discard. It would be an interesting experiment to try to reuse the pickle however…
Nothing against experiments, but there isn’t much to experiment, really. These chemical processes are replacement processes where the replacement goes from higher value to lower value (very simplistic).
If you dissolve silver (Ag) in nitric acid (HNO3), you will loose the hydrogen H and end up with silver nitrate AgNO3. To get the silver out (it’s still an acid), you could dissolve copper in it, cementing out the silver, ending up with copper nitrate CuNO3. To get the copper out, you could use iron, ending up with iron nitrate FeNO3. Not sure what to use to get the iron out, but already at the copper level, this isn’t an economically operation.
But whatever, you can’t climb the ladder up (Fe > Cu > Ag), nor will you get the missing hydrogen H back in, needed for the reaction to start.
TLDR : Forget it. Neutralize your pickle and dump it (or use in ceramics or as fertilizer in your garden).
Following the steel wool dip, all the cooper would be replaced by iron, and all the acid would be used up in dissolving what steel wool is left. Pickle is spent. It would be possible to electro plate the copper out, but at the price of pickle (Ph Down or NaHSO4, sodium bisulfate), why bother. As far as copper pollution, that would be removed by the steel wool. What I do not understand is that it is fine to poor a pound or 2 of straight copper sulfate (AKA Root Kill, CuSO4·5H2O) down the drain, but not a few grams of CuSO4 in used pickle. Another way would be to neutralize the spent pickle with washing soda, Na2CO3 or backing soda NaHCO3- lots of fizzing. This will form insoluble copper carbonates and other odd insoluble salts. Let them settle out, pour off the neutralized liquid, let the solids dry an discard in the solid waste stream, or save a life times worth and discard a pound with hazardous waste people.
I am learning so much. I had no idea that the iron would replace the copper in solution… I am not sure if I missed this in school because it wasn’t taught or because I wasn’t there- either way, thank y’all for the practical chemistry lessons.
