Author Topic: Disposing (or Regenerating) Sodium Persulphate etchant  (Read 5082 times)

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Offline will_raymo2000Topic starter

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Disposing (or Regenerating) Sodium Persulphate etchant
« on: December 06, 2016, 10:24:56 pm »
Having been using my first batch of persulphate for a month or just over its finally given all it can give and won't etch any more! I realise that obviously I can't just pour it down the drain, so my question to the experts is what can I do with my expired etchant?

I have read on some other forums found from google searches that you can do some kind of electrolysis to regenerate the persulphate to use again? Has anyone had any experience with this?

Thanks,
Will
 

Offline Quiggers

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Re: Disposing (or Regenerating) Sodium Persulphate etchant
« Reply #1 on: December 19, 2016, 01:30:03 pm »
Home users are best neutralising the Ph and then using a local council recycling centre to dispose of, they generally have large containers of oils, paints and solvents.

Get some litmus paper, add some base to counteract the acid, baking soda is suggested in this thread


https://www.eevblog.com/forum/projects/pcb-etchant-disposal/

once it's Ph neutral I should be safe to add it to the recycling tank at your local tip.
Any aciddity will mix with oils to make soap, salt and water.

What the council then does with the gallons of mixed chemicals is anyone's guess.

Also ask before you tip it in.
 

Offline DTJ

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Re: Disposing (or Regenerating) Sodium Persulphate etchant
« Reply #2 on: December 19, 2016, 01:45:19 pm »
I thought the way to make spent sulphate etchant safe was to stick a wad of steel wool in it.

All the nasty copper ions will plate out on the steel wool, then it can be safely disposed of.
 

Offline technotronix

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Re: Disposing (or Regenerating) Sodium Persulphate etchant
« Reply #3 on: December 31, 2016, 10:55:27 am »
I really don’t have an experience with this but I think Quiggers has suggested a good way to Regenerating Sodium Persulphate etchant.
 

Offline jpanhalt

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Re: Disposing (or Regenerating) Sodium Persulphate etchant
« Reply #4 on: December 31, 2016, 11:04:41 am »
I really don’t have an experience with this but I think Quiggers has suggested a good way to Regenerating Sodium Persulphate etchant.

Quiggers is not talking about regeneration the persulfate.  He describes a method to dispose of the "hazardous" waste after converting it fully to a sodium sulfate.  I would not consider wasting the resources available for hazardous waste disposal in that way.   

Some people are concerned about the tiny amount of copper in the waste.  In my area, copper sulfate is added regularly to ponds and septic systems to inhibit tree roots and other vegetation.

John
 

Offline DTJ

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Re: Disposing (or Regenerating) Sodium Persulphate etchant
« Reply #5 on: December 31, 2016, 02:53:22 pm »
A decade ago we were using ammonium persulphate at work. I called the water authority guys and they just said to dump it down the drain. It may be a different story if the volume was higher.
 


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