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Reclaiming Copper from Sodium Persulfate #1: The Naive Approach

At shackspace we’re somehow in the business of collecting sizable amounts of used up etching solution. We’re using Sodium Persulfate which on its own is also used as a bleach, detergent or disinfectant.
However, with plenty of copper ions in the used up solution it’s a very potent poison and you should not by any means pour it down your drain, ever.

A quick search on how to get rid of the stuff yielded Marc Schaffer's page (German) who explains his electrolysis setup using a 12 V 900 mA Photocell, a copper cathode and an anode made from either stainless steel, coal or platinum.

Platinum was no option because of its high price. I didn’t have any stainless steel that I could verify to be stainless steel at hand, so I opted for coal.
The closest thing to coal I could think of was graphite.
And since I’m a lazy person, I simply got some sketch pencil leads. All the core, none of the casing :)

The result of the first experiment can be seen in the pictures above:

  • The pencil lead disintegrated
  • A huge mess

What I’ve learned:

  • 12 V won’t work. Anything much higher than 2 V will cause the lead to disintegrate
  • Electrolysis should start at around 1.8 V, that’s when bubbles (Oxygen) start to form at the anode
  • Graphite particles can be filtered out quite easily using a piece of paper towel
  • More electrodes should have better yield
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