# Spent AP Solution -- How to properly discard?



## TheArchitect (May 29, 2008)

Can anyone illustrate me to the proper way to neutralize and discard my spent AP solution? i've successfully reused the solution for 3 batches dissolving fingers by rejuvenating w/ H2O2... i've read about dropping out the base metals w/ aluminum.... will sodium hydroxide neutralize the remaining solution? to a pH of 7? 

any help would be greatly appreciated. thanks in advance... -Mitchell


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## agpodt77339 (May 29, 2008)

Test with stannous, if there are any PM's, then cement them out with copper. Then put in a piece of scrap iron/steel to cement out the copper. After the copper is out, add baking soda to neutralize it.


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## Oz (May 29, 2008)

I have heard but don’t know for fact that iron can mask the indication of gold with stannous. Maybe someone can conclusively confirm or deny this as a lot of people are using AP on plated ferrous materials. 

You could also use a bubbler for introducing oxygen into your solution instead of diluting it with H2O2. The added benefit being that when it is eventually saturated with copper it will precipitate any dissolved gold as a fine black powder. If you have diluted your solution with too much H2O2 you may need to add some more HCl. I recently added a bubbler to mine and it has greatly sped up the process.


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## hungry (May 29, 2008)

OZ

What did you use to get a fine aeration on your bubbler. I tried a couple of aquaruim stones and they worked fine until they broke down into particles.

Thanks,

ED


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## Oz (May 29, 2008)

Hey hungry,

I used an aquarium pump good for an 80 gallon aquarium and just ran aquarium hose straight down into the solution through the lid. I had planned on 2 inputs but I am only running a gallon of solution or more. As I do bigger batches I may find I need more.

Down the road I would like to set it up as a vacuum system so it pulls the air into solution. That way I always have negative air pressure in the reaction and it could be in my work area instead of outside.

Oz


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## lazersteve (May 30, 2008)

Ed,

You can take a piece of hose and seal one end off, then drill very small holes along the end length of the hose that will be submerged.

Steve


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## Irons (May 30, 2008)

lazersteve said:


> Ed,
> 
> You can take a piece of hose and seal one end off, then drill very small holes along the end length of the hose that will be submerged.
> 
> Steve



If the opening on your container is big enough, you can coil it and hot glue it to the bottom of the container


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## hungry (May 30, 2008)

Oz, Steve, Irons,

Thank you all for your your creative replies.
Like they say necessity is the mother of invention and this hobby (so far) is one that requires the most.
I have spent a bit of money on this and finding a way to do some things cheaply is a delight.
How about having a topic in the index on how to do things cheaply or creatively that members have found to work for them. This way when someone has a problem, they can access the topic to maybe find some clues to help them. Something to think about.

Thank you,

ED


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## TheArchitect (May 30, 2008)

so that's it... drop in some steel/iron to drop out the metals... and then mix in some baking soda to the remaining liquid to neutralize?


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## Oz (May 31, 2008)

That would do it if you don’t want to continue using your solution


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