Try concentrating the metal (RO or ion exchange followed by regeneration using 
sulfuric acid to as the counterion) and plating it out. Who cares how poor the 
deposit looks, as long as the metal plates.

Alternatively, you can plate it direct using a fluidized be of metal balls in 
the liquid stream (between shielded electrodes).

______________________________ Reply Separator _________________________________
Subject: Tin strip issue
Author:  "DAVID DUROSS" <[log in to unmask]> at INTERNET
Date:    6/18/97 3:45 PM


We currently use tin as a primary etch resist and a nitric-acid based tin 
stripper.
We are experiencing difficulties with waste treating the spent stripper:
* Tin is OK to go to drain, but NOT the copper. We would prefer to recover the 
tin, also.
* Precipitation is possible but only after a 4:1 dilution recommended by the 
vendor of the stripper and by vendors of flocculants which generates more 
liquid waste.
* The precipitated tin is very fine, even with precipitation aids, and when 
the precipitate enters the filter press, it clogs the press rapidly.
     
Are there any means or methods to accomplish waste treating nitric-acid based 
tin strippers to recover the tin and to treat the copper? Any alternative 
methods possible?
     
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