# Why did pgms redissolve in copper saturated solution



## Slaughlin79 (Feb 23, 2020)

I’ve been cementing there last of the redissolved pgms from cat solution and something happened that I thought impossible.

I put a pice of shiny copper pipe in pgm solution and heated and everything was going very nice and was getting nice thick flakes of pgms like in the picture but, when the solution got saturated with copper and copper chloride started to cane out of solution almost all my pgms redissolved. The first time it happened I thought i was just seeing thing but but a stannous test confirmed it. 

The second time tested with stannous multiple times and like the first when all pgms were just about cemented copper chloride start precipitating and pgms are redissolved. I don’t understand what is going wrong? Can someone please tell me? Now I’m adding water to get more of the copper to drop and then I’ll filter and concentrate and add water and drop copper and repeat till I stop getting any and try to re cement pgms. This has been happening and I’m sure now I’ve lost lots of values bc I was obvious what was happening. I’m so ready to be done with this crap and will never do it again but I don’t want to pour this down the drain for a lot of reasons,mainly environmental but if I can’t get any help I don’t see another option because I’ve read and read and never came across anything like my issue.


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## Lino1406 (Feb 23, 2020)

It's assumed that better de-noxing (or free chlorine removal by same additions) before cementing will help, as less copper will go directly into solution instead of reacting with PM's ions first. Of course, copper saturated solution will also stop the conversion process.


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## Slaughlin79 (Feb 25, 2020)

I agree completely but in the picture you can see how the pgms are cementing out nicely. I never removed the copper pipe and the solution got saturated with copper so much so that white copper chloride was forming at the bottom. I’m not being a smart ass I swear to god when I ask this But, are you says that there was enough free HCl to redissolved pgms but not enough for pgms to continue cementing? 

I could see a scenario where that could play out but the solution was heated for two days in the sunlight so all chlorine gas from h2o2 should’ve been driven off I would think.

It seems the only way to remove the copper is to keep evaporating and adding water and filtering the solid copper chloride and repeat until copper stops coming out. Does this sound like an okay way to remove most of the copper from the solution so I can recement?


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## Lino1406 (Feb 25, 2020)

The other way round - add water to dissolve CuCl2 bellow saturation. Of course, at one stage consider disposal


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