LProcess said:
Hi Dave,
thanks for your reply.
But cementing palladium on copper is slow and is very difficult remove the palladium on the copper surface.
The best way is drop the copper like metal or salt, but i don't know how i do it.
Thanks
LProcess
Hi & welcome to the forum
Per the underlined - my first question is - when trying to cement the Pd with copper are you just simply putting the copper in your solution & letting it sit there ? --- or are you adding some kind of agitation to the solution such as a bubbler or constant stirring of the solution ?
I ask because when cementing PGMs "without" agitation will cause the PGMs (Pd in your case) to "adhere" to the copper which then create a passivation layer on the surface of the copper
This passivation layer on the copper can/will cause the cementation process to slow down - even to the point of stopping the cementing thereby preventing full recovery of the PGMs from the solution --- & as you already pointed out - removing the passivation layer from the copper is difficult if not impossible
By providing "constant" agitation to the solution the solution is in constant motion with the surface of the copper & that constant motion does not allow time for the PGMs to adhere the surface of the copper but instead keeps them "washed off"
The more aggressive the agitation the better
You have two options when cementing with copper (along with agitation)
1) using "fine" copper powder - this needs "constant" stirring for the agitation in order to keep the fine copper powder in suspension during the cementing process
2) heave pieces of copper (like copper bus bars) "suspended" in the solution along with a bubbler for the agitation
start you agitation "before" adding the copper other wise if you add the copper before starting the agitation the PGMs will "start" the cementing which will allow the passivation layer to get a head start
Here is a link to a "detailed" discussion about cementing PGMs with copper which details the problems & the solutions - the real discussion starts about 3 or 4 post down with my first post in the thread
:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=21218&hilit=cementing
Kurt