solarsmith
Well-known member
Can cupuric sulfate be used in place of a copper bar for droping pgms? any details would be greatly appreciated. Bryan In Denver Colorado.
CUPRIC SULFATE
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No! Only Cu metal will work.solarsmith said:
Bryan,
The elemental copper metal Cu0 the atoms of the copper metal have all of their electrons. when it is in an acidic solution of metal ions, the copper will only give up electrons to a metal ion in solution that is less reactive than the copper metal (see the reactivity series of metals), the more noble metals, these metal ions in solution are called cations, the solution would also contain anions such as chloride ions.
Take a solution of gold chloride for example.
Here the gold metal has lost electrons and is oxidized into a solution as ions of gold called gold cations Au+3, along with the three chloride anions Cl-(from the acid which took the gold atoms electrons). the gold and the acid are now salts of their former selves. the gold ions need three electrons to be reduced back into elemental gold atoms Au0 which will cluster together to form the gold precipitant (tan brown powder when fairly pure).
The copper Cu0 metal will donate electrons to the gold ions (they must come into direct contact with the copper metal), the gold is less reactive than copper (reactivity series), the gold ions gaining these electrons is reduced back to elemental gold atoms which cluster and fall out of solution with gravity. The copper losing its electrons is oxidized into solution as copper cations Cu+2, or into a solution of CuCl2.
The copper bar will not give up electrons to metal higher in the reactivity series than copper (so these other metal cations that may have been in solution with your gold stay in solution with the copper chloride ions...
(Note the cleaner the solution the less drag-down and other contamination, the thicker the copper the less chance of particle of copper metal contamination...)
Now let's discuss: Why copper sulfate will not reduce gold from solution.
The copper in the copper sulfate has already lost its electrons, it is a salt of the copper metal a salt of copper and sulfuric acid consisting of copper cations and sulfate anions. The copper salt has no spare electrons to give your gold ions, so adding the copper sulfate to your gold chloride solution would just put more ions in solution (gold copper and other metal cations, and chloride and sulfate ions all dissolved in one metal salt soup.
So adding copper sulfate to gold chloride does nothing but contaminate your solution with more ions to deal with later.
Basically no chemical reaction occurs, no electrons are moved...
The elemental copper metal Cu0 the atoms of the copper metal have all of their electrons. when it is in an acidic solution of metal ions, the copper will only give up electrons to a metal ion in solution that is less reactive than the copper metal (see the reactivity series of metals), the more noble metals, these metal ions in solution are called cations, the solution would also contain anions such as chloride ions.
Take a solution of gold chloride for example.
Here the gold metal has lost electrons and is oxidized into a solution as ions of gold called gold cations Au+3, along with the three chloride anions Cl-(from the acid which took the gold atoms electrons). the gold and the acid are now salts of their former selves. the gold ions need three electrons to be reduced back into elemental gold atoms Au0 which will cluster together to form the gold precipitant (tan brown powder when fairly pure).
The copper Cu0 metal will donate electrons to the gold ions (they must come into direct contact with the copper metal), the gold is less reactive than copper (reactivity series), the gold ions gaining these electrons is reduced back to elemental gold atoms which cluster and fall out of solution with gravity. The copper losing its electrons is oxidized into solution as copper cations Cu+2, or into a solution of CuCl2.
The copper bar will not give up electrons to metal higher in the reactivity series than copper (so these other metal cations that may have been in solution with your gold stay in solution with the copper chloride ions...
(Note the cleaner the solution the less drag-down and other contamination, the thicker the copper the less chance of particle of copper metal contamination...)
Now let's discuss: Why copper sulfate will not reduce gold from solution.
The copper in the copper sulfate has already lost its electrons, it is a salt of the copper metal a salt of copper and sulfuric acid consisting of copper cations and sulfate anions. The copper salt has no spare electrons to give your gold ions, so adding the copper sulfate to your gold chloride solution would just put more ions in solution (gold copper and other metal cations, and chloride and sulfate ions all dissolved in one metal salt soup.
So adding copper sulfate to gold chloride does nothing but contaminate your solution with more ions to deal with later.
Basically no chemical reaction occurs, no electrons are moved...
solarsmith
Well-known member
wow thats a realy good explaination of it. so to drop gold and pgms lower than copper I should use heavy copper bar pipe or wire. I will be dropping from aquaregia solution and could you sugest a ph for this?
thanks Bryan in Denver Colorado.
thanks Bryan in Denver Colorado.
I must be reading wrong that you've been a member for 7 years with 180 posts.
solarsmith
Well-known member
I have only found one mention of a ph for droping pgms here and its a ph of 1 plus or minus 0.4 .
I have seen in other places the ph for droping run from 3 to 7 .
a friend is telling me to drop gold first at a ph of 4 to 5 and all of my reading has the pt being droped first.
this is my first time working with pgms in a mixed situation. and am just trying to get a good base of information from the experts. im getting good drops with smb but thay have a lot of red mud with the brown tan precipitant. I think it might be due to pt droping with it. and then after a lot of reading I find I probly should have been droping the pt first then pd then gold then ag Bryan In denver
I have seen in other places the ph for droping run from 3 to 7 .
a friend is telling me to drop gold first at a ph of 4 to 5 and all of my reading has the pt being droped first.
this is my first time working with pgms in a mixed situation. and am just trying to get a good base of information from the experts. im getting good drops with smb but thay have a lot of red mud with the brown tan precipitant. I think it might be due to pt droping with it. and then after a lot of reading I find I probly should have been droping the pt first then pd then gold then ag Bryan In denver
Bryan, as you've seen, pH can be important when dealing with tricky drops from solutions containing both gold and PGMs. From what I've read, either can be dropped first, but it is usually preferable to drop the one in the highest concentration first.
But that assumes you're using a selective precipitant.
Copper doesn't care. It will drop everything below it (less reactive) on the reactivity series. Cementing on copper is a good way to recover all the precious metals in a solution, but it will not help to separate them.
Dave
But that assumes you're using a selective precipitant.
Copper doesn't care. It will drop everything below it (less reactive) on the reactivity series. Cementing on copper is a good way to recover all the precious metals in a solution, but it will not help to separate them.
Dave
Topher_osAUrus
Well-known member
solarsmith said:
Use copperas to precipitate gold first if you are just going to collect the pgm's by cementation on copper.
If you are reclaiming pgm's with NH4Cl then chlorate(if Pd recovering), its better to do them first if you have appreciable quantities in solution, since they need to be dropped from a concentrated solution. If you precipitate the gold first, generally the solution gets diluted then you have a heck of a time going after pgm's
I cant remember the thread, but one says gold precipitates best around 1.5-2.5pH, But, Ive never had issue with pH and precipitation (so long as it is acidic enough to release SO2 from the smb),I don't the restricting factor is pH, but free nitric. Too much of it, and the gold may never fully drop. Then cementing is your only salvation.
SO2 can reduce Pt and Pd if the solution is around 7, (Lazersteve posted a precipitant chart on here) Ive also read the SO2 gas can create sulfite complexes with Pt and its best to avoid them.. Honestly, can't say if I have had that problem, as I always reduce the gold and then cement the pgm's and save up the black powder.
Bryan be aware that PGMs in solution pose a serious health risk as do their salts if you are trying to precipitate them out, be sure to wear gloves and work with a fume hood if this is the route you are going.
If you have a chloride solution you only have trace amounts of silver. Nothing worth trying to recover.solarsmith said:
Personally, if I have decent amounts of gold and PGM:s then I precipitate the gold first using SMB or copperas. Next I cement all the remaining PGM:s with zinc if there is almost no copper in solution, or with copper if it is too dirty. The resulting black powder can be saved up until there is enough to warrant a refining to separate the PGM:s. It is also easier to make a concentrated PGM solution, starting with the black powder, so you can use normal precipitants for palladium and platinum.
Palladium can always be recovered with DMG (dimethylglyoxim) even from a dilute solution but DMG is a rather expensive precipitant.
Göran
