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January 1997

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Wed, 15 Jan 1997 08:12:43 +0000
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Michael,

Thanks for the info.  I would be interested in any data you have.  
There are some other resins that R&H do not make that are available 
on the market.  I think I also saw an article in the last few years 
about removing impurities from gold solution that I will check on.  
There has been a lot of work done on this type of application by the 
gold mining industry in South Africa (heap leaching and all that).   

The trick is to find a resin that prefers the nickel over the gold or 
to find a pH where the gold is more tightly chelated (in the gold 
solution) than the nickel. 
  If you can find a spot where the nickel is preferred by the resin 
and the gold is preferred by the cyanide,  you can use a very small amount of resin that first saturates with the gold then 
exchanges the gold for nickel.  Gold will always overwhelm the resin 
first but it should replace with nickel if the conditions are 
correct.  Using a very small amount of resin reduces gold loss.

Bob Mesick


> Date:          Wed, 15 Jan 1997 06:40:59 -0600
> From:          [log in to unmask] (Michael Holan)
> Subject:       Re[2]: Ni Resins for Gold Plating
> To:            [log in to unmask], Bob Mesick <[log in to unmask]>
> Cc:            [log in to unmask]

>      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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