We have been trying to accomplish the task of removing the nickel for 
     a couple of years now.  We have worked with all the Rohm & Haas resins 
     that are available.  The separation does not work because the nickel 
     forms an extremely stable complex with cyanide.  The best separation 
     that we have been able to achieve also removed 30% of the gold.
     
     We have also tried phase separation via creating a insoluble salt of 
     nickel.  These work about as good as the resin approach.  About 30% of 
     the gold precipitates as well and there remains in solution a anion 
     that may affect the plating from the bath.  The plated deposit from 
     the bath has to be reevaluated to make sure it will meet 
     specifications.  
     
     I have also talked to several of the diffusion dialysis manufactures.  
     They have told me that there are no membranes that will perform this 
     separation either.
     
     Suffice it to say that we have not yet found a practicle approach to 
     removing the nickel from the cyanide soft gold bath without affecting 
     the deposit properties.
     
     If you would like to get more details on the experiments that we have 
     performed, please contact me in person.
     
     
     Michael Holan
     Process Engineer
     Radian International, L.L.C.
     Electronics Division
     
     ph.  512.310.4209
     fax  512.388.0898
     internet:  [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Re: Ni Resins for Gold Plating
Author:  Bob Mesick <[log in to unmask]> at Internet
Date:    1/14/97 11:52 AM


Steve,
     
There are resins that would be pretty specific for nickel in a gold 
solution.  The chelated resins (IDA or AP) would be suitable providing that 
there are no other metal ions that have to be in solution.  The resin will 
remove all cation metal ions and leave in sodium, potasium, and hardness 
ions (at low pH).  
     
I haven't worked with gold solutions since the early 80's (was a microplate 
guy) so I'm a bit out of date.  I assume soft gold is gold only with 
potassium salts and I'm guessing that the pH is less than 5 but I don't know 
off the top of my head anymore.  You would have to adjust the resin before 
use to keep the exchange group compatable with the bath.
     
I could get you a ounce or so of resin to try on a small sample of gold. 
You would have to prep the resin first before trying.  The resin will not 
remove the gold as it pretty well locked in the cyanide complex.
     
The simplest test would be to prep the resin, take about 5 cc's of gold 
solution, add about 5 beads of resin to the solution and mix for 2-3 hrs 
(makes up for not using a column).  Check the nickel, gold, pH and other 
parameters.  This should tell you if it will work.
     
I you want a sample, send me your bath analysis so I can be sure I know what 
I'm talking about.
     
Bob Mesick
     
     
At 02:42 AM 1/14/97 CST, you wrote:
>------------------------------
     
>
>Date: Mon, 13 Jan 97 23:16:34 PST
>From: <[log in to unmask]> (Steve Sparkowich) 
>To: <[log in to unmask]>
>Subject: Ni Resins for Gold Plating
>Message-Id: <[log in to unmask]> 
>Content-Type: text/plain;
>               charset=US-ASCII
>
>Do any of you Gold electroplaters use an  ion exchange resin specific to 
>removing Nickel from a soft gold bath?  If so, I'm interested!
>
>[log in to unmask]
Remco Engineering (remco.com/home.htm)
Industrial Water and Wastewater Treatment Systems 
San Luis Obispo, California  USA
     
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