What's the safe way to dispose of used copper etchant?

I've been using Ammonium Persulphate, the instructions just say to "Follow
your local authorities recomendations on disposal.".
Who is the local authority in Aus?
Just how toxic is the stuff - I'm thinking I'll just dig a hole out the back
and pour it in.
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Your local government (council) should be able to advise you on this. Alternatively and probably better - consult your old high school chemistry books and see if there is something you can mix with it to turn it into something useful like Ammonium Sulphate which can be used as a fertiliser on your plants. Any precipitated copper can then also be used as a trace element. :)
Cheers, Alan
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Alan Rutlidge
That would probably be your state EPA department.
That's what I do for the small quantity I use. Although it would be best to save it up and dispose of it at your local council chemical cleanup day (if you have one). We had ours the other week and it was so popular that there was an hour long wait to get in!
After using ferric chloride as a kid and hearing talk about not pouring it down the sink, it was interesting to find out that Sydney Water actually add it to our drinking water! Not that I drink tap water anyway :->
Dave :)
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David L. Jones
Don't do what I did.
I stored it in a soft drink bottle, and after a few months, it evolved enough gas to burst the bottle, and etchant went everywhere. I have pressurised those softdrink bottles to more than 150PSI without them bursting, so I hate to think how much pressure was in there when it did burst. To add to the embarrassment, it happened whilst we had guests staying over. I had labelled the bottle with lots of stickers saying "Toxic", so I don't think they were amused when it went everywhere.
In summary, make sure your bottle has an air vent!
Reply to
Chris Jones
You could always evaporate it, and end up with crystals mostly of copper sulphate and a bit of ammonium sulphate (if you've used the etchant a lot). I have a few jars of big blue copper sulphate crystals as a result.
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Or just add it to your drinking water - our government encourages industry to use our kidneys to filter their waste flouride like this every day.
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(Just) Allan
This stuff is excellent for discouraging termites. Mix copper sulphate with an equal quantity of calcium carbonate (crushed limestone) and mix with water (100g per litre), pour it in small quantities (100ml per tree) round the base of your favourite trees and termites will not trouble for at least a couple of years.
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Contact your local Council or EPA.
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About 5 yrs ago I contacted WA Water Authority asking about disposal, the answer: Tip it down the sink with a heap of water behind it.
Sometimes we tipped it down the drain, some times it went out with lab waste (at a cost of ~ $1/L).
We would have been generating 20 --> 30 L of spent solution per year.
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