ooh - permanganate bad!  This was the industry standard many years ago, but people got away from it for precisely the reason you mentioned, i.e. buildup of manganese in the solution.  The industry standard for many years has been hydrogen peroxide followed by heating to drive off (destabilize) the peroxide and followed by adding granular or powdered carbon to absorb the organics.  Like you, I have seen situations where peroxide alone has been insufficient to remove all organics.

I have been quite successful by adding 1/4 ml/liter of common household bleach (a solution of 5.25% v/v sodium hypochlorite; NaOCl) in 3 increments (add 1/3, wait 20 minutes, add the next 1/3, wait 20 minutes, and then add the last 1/3) followed by carbon polishing.  All of these methods utilize a strong oxidizer to "break up" the organic chains into portions which can be then attached to the carbon; the bleach is another strong oxidizer which has the advantage of not requiring heat treatment or adding bulk carbon to the solution and adding only a few ppm of chloride to the bath.  I promise, it really works very well and is much, much easier to do.

While you're at it, the next time you pump your copper bath out of the tank, if you have a polypropylene or polyethylene tank you might fill up the tank with a solution of 10% sodium hydroxide and 1/4 pound/gallon (120 g/l) of trisodium phosphate.  Use hot water to make this up if it's available; after an hour or so the solution will be brown from all of the soaked-in organics it will remove from the plastic tank.  Drain and neutralize with a weak sulfuric acid solution.

Regards,
Fred J.

>>> Paul Gould <[log in to unmask]> 10/12/98 04:32am >>>
Does anyone have information regarding the treatment of copper sulphate plating solutions for organic contamination. 

We do this approximately once a year on all solutions and have been using the following method:-
0.5-1.5gm/litre  of Potassium Permanganate depending on level of organics
Agitate for 2 hours
0.5 ml/litre of 35% Hydrogen Peroxide
Agitate for 1 hour
Heat to 60 C (140F)
Add 2gm/litre of activated carbon 
Continue with heat and agitation for 2 hours
Allow to settle and filter pump to storage tank as soon as possible to prevent organics leaching back into solution from carbon.
 
Conversion factors ( g/l x 0.134 = 0z/US gal) & (1 litre = 0.264 US Gals)

This method is very effective at removing the organics but I would like to know more about how this works. My concern is the level of Manganese left in the solution after treatment. We recently tried using peroxide only and carbon but this did not reduce the organics sufficiently. We are told there is a finite number of times where permanganate can be used before the bath has to be replaced.

Is this method likely to cause a build up of manganese and is there any alternative?

Many thanks for any information
Paul Gould
Teknacron Circuits Ltd

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