SylviaElse
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Ammonium persulphate disposal
I had lying around about four litres of ammonium persulpate solution, mixed with some copper sulphate. This had been used to etch circuit boards. I
decided I didn't want to keep storing it, so looked for a way to neutralise it, or at least make it more disposable.
I decided to dissolve iron into it, in the form of steel wool, to convert it to ammonium ferrous sulphate (this took a while because it generates a
lot of heat). It worked to a point, in that the steel wool would be instantly coated with copper, but the acid was able to act and dissolve both the
copper and the steel.
Eventually, though, presuambly when the acid was gone, the steel would just be plated with copper, and not react further. I've managed to plate quite
a lot of steel wool with copper, but there's clearly more copper in there.
I've pondered using iron filings (more expensive) to complete the process, but would I encounter the same problem?
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woelen
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The problem you have is that there is a lot of excess persulphate in the solution and this oxidizes both iron and copper. Only when this is used up,
you can plate out all copper and make a solution of iron-ions and then flush it down the drain.
I am afraid you will need a lot of iron to first react all persulphate and next plate out copper.
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SylviaElse
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I think as long as there's persulphate there, I should be able to get the iron to dissolve, but I've reached the point where iron that I add gets
plated with copper, and then just sits there because there's nothing to remove the copper so as to expose the underlying iron to further reaction. The
amount of iron I've managed to dissolve about fits my estimate of how much would be required based on the amount of persulphate involved.
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XeonTheMGPony
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electrolysis? drive the reaction by chosing the target to be plated with an electrical potential while the anode is put into solution.
So two chunks of iron and a low tension power suply
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