First Go at Electrorefining Silver

[Long Shot]

Today I made my first attempt at the silver cell on a benchtop small scale. I am now on my second of four "doorknobs". It seems to be going good and the cell temperature is warm but not hot. I started off a little high in the volts to get things going then reduced to 9V, 2 amps, getting nice crystal. I made my electrolyte out of my last batch of contacts, twice refined, and multiple hot water rinses to get as much copper out as possible. On the second refinement I dissolved two 3/4 oz sterling medallions I had for good measure. My knobs weigh up at over 7 ozt and am looking forward to the outcome.







Dollar store basket made from a funnel type thing (I think it was intended as a floating pool drink glass) which is perfect for the 1L beaker, cloth is fine weave muslin.

 

[FrugalRefiner]

Your voltage is too high. You risk codepositing other metals along with the silver.

Your electrolyte is fairly colorless. I would expect it to be more blue in color. That may indicate that base metals are plating out.

Dave

 

[Long Shot]

I turned it down Dave - the photos were from much earlier in the day. The electrolyte was very pale at the beginning, is now blueish. The basket looks as I would expect, darker deposits or slimes in the bottom, crystals look really good. Currently voltage is at 3, amps at 0.7.

 

[Palladium]

Looks like your starting solution is weak on the concentration side. I notice this from the thin spinney growth of the crystals. This is a reaction of the voltage being so high to push more amps. Boost you solution strength either by not diluting it so much or adding more silver nitrate. Then the amps will come up, the crystals will fatten up, and your voltage will drop. Looks like you might be using a small block of graphite. Some of it probably has to do with that graphite cathode size your using to. Get a stainless bowl and spread your cathode area out some and concentrate your solution. Don't have a lot of silver at one time to run then reduce your solution size by concentrating it and find a miniature bowl for a small version of the cell.

 

[Long Shot]

Palladium - I estimate 3 to 3.5 ozt of silver in solution (900 ml). I came up with that value based on using old, selected contacts that, although alloyed, I believed to be high in silver content (no way of knowing for sure). As stated, I dissolved them, cemented with copper, washed the cement, let it dry somewhat and re-dissolved with the addition of two 3/4 ozt sterling medallions, re-cemented, re-washed until I was getting clear supernatant, filtered it. I then put this in solution with 50/50 nitric/DI and let it sit in the dark for awhile until my power supply arrived. It may be lean. Also, it is not a graphite cathode, and this is likely my problem here, what you see is a piece of insulated 18 ga copper wire, what you don't see is a strand of .99 silver wire which is silver soldered onto the copper - that joint is sealed with heat shrink. The silver wire is the same gauge as the anode wire. Resistance measured 15.4 ohms at start up. It is good advice about the SS bowl and I have read those threads about that (Kadriver for example). Going forward I am going to search for some different stuff to build it like that. This is only a hobby and live and learn sort of thing, I am trying to keep the costs down so look for things I can improvise to do so. I am reluctant to dissolve my pure silver bars to make the electrolyte but after this foray I think I will do that. Thanks for the positive contribution.

 

[g_axelsson]

Do you mind if I change the topic to electrorefining from electrowinning? Electrowinning is the process of recovery of metals from solutions using electricity with an inert anode.

http://en.wikipedia.org/wiki/Electrowinning

Göran

 

[goldsilverpro]

Do you mind if I change the topic to electrorefining from electrowinning? Electrowinning is the process of recovery of metals from solutions using electricity with an inert anode.

http://en.wikipedia.org/wiki/Electrowinning

Göran

You beat me to it.

 

[Long Shot]

Goran - no problem, excuse my ignorance. FYI to all, I abandoned this today in favour of a fresh start.

 

[nickvc]

Goran - no problem, excuse my ignorance. FYI to all, I abandoned this today in favour of a fresh start.

Well I think you have learnt a few things thats what a set back should be about, dont give up just rethink it and start again and with the help available here you should be totally successful.
Keep us informed of your new set up and I'm sure you will get helpful hints and comments so that your next cell performs as you hope.