After several successful refinings of karat and gold-filled scrap, I decided to try my hand at recovery from e-waste. I purchased about 500 g of old Soviet ICs and capacitors on eBay and smelted it in a Devil Forge propane furnace, using a flux consisting of sodium carbonate and borax plus 10 g of silver as a collector metal. I kept the air wide open to generate as hot and oxidizing an environment as possible in order to minimize emission of organic carcinogens, and my pyrometer indicated it reached about 1400 C. After pouring the melt into a cone mold, I chipped the slag off and got a metal cone of about 65 g. It was moderately magnetic indicating that there was quite a bit of iron, nickel, and/or cobalt in the alloy.
I tried dissolving this in 1:2 nitric with distilled water, but it was very slow even after adding about 8 mL of sulfuric per a suggestion I found by Geo. After two full days on heat and five days sitting at outdoor ambient temp, I poured off the solution. The metal cone was still intact and had lost only about 10 g, having been coated by a passivating layer of a purplish-pink substance, the same as I would get later. I remelted the ~55 g of metal with 78 g of sterling silver plus a similar amount of soda/borax flux, hoping to get rid of the oxides and dilute the passivating base metals out with silver and copper. This produced a metallic button, with the pink stuff going into the slag. I then repeated the nitric treatment.
It has gone much better this time, with most (but not quite all) of the metal eventually going into solution. I just decanted it and noticed that there is a lot of the same magenta stuff left in the beaker. I’ve done some tests but still am not sure what it is, so I'm wondering if anyone knows what it might be.
I tried digesting a sample of it in HCl+H2O2. It did go into solution then, seeming to make the tech. grade HCl a little more yellow (which might just have been Cl2) but not generally changing the color much. A stannous test was negative. DMG revealed no palladium but did show quite a bit of nickel when I added ammonia to raise the pH. A thiocyanate test was positive for iron, but the color was more orange than blood-red, indicating a fairly low concentration. I tried a crude cobalt test by adding dichloromethane to the thiocyanate solution, but nothing extracted into the organic phase. I’ve read that cobalt thiocyanate can give a blue color when extracted into an organic solvent but I’m not sure if my choice of solvent is a good one.
I'd think it was mostly nickel, but nickel oxide and most nickel salts are green. Some of cobalt's soluble compounds are red or pink, but it seems cobalt(II) oxide is black and I'm not sure if it has any insoluble compounds that match the magenta color.
Does anyone have any idea what this could be? I’ve attached a picture below.
I tried dissolving this in 1:2 nitric with distilled water, but it was very slow even after adding about 8 mL of sulfuric per a suggestion I found by Geo. After two full days on heat and five days sitting at outdoor ambient temp, I poured off the solution. The metal cone was still intact and had lost only about 10 g, having been coated by a passivating layer of a purplish-pink substance, the same as I would get later. I remelted the ~55 g of metal with 78 g of sterling silver plus a similar amount of soda/borax flux, hoping to get rid of the oxides and dilute the passivating base metals out with silver and copper. This produced a metallic button, with the pink stuff going into the slag. I then repeated the nitric treatment.
It has gone much better this time, with most (but not quite all) of the metal eventually going into solution. I just decanted it and noticed that there is a lot of the same magenta stuff left in the beaker. I’ve done some tests but still am not sure what it is, so I'm wondering if anyone knows what it might be.
I tried digesting a sample of it in HCl+H2O2. It did go into solution then, seeming to make the tech. grade HCl a little more yellow (which might just have been Cl2) but not generally changing the color much. A stannous test was negative. DMG revealed no palladium but did show quite a bit of nickel when I added ammonia to raise the pH. A thiocyanate test was positive for iron, but the color was more orange than blood-red, indicating a fairly low concentration. I tried a crude cobalt test by adding dichloromethane to the thiocyanate solution, but nothing extracted into the organic phase. I’ve read that cobalt thiocyanate can give a blue color when extracted into an organic solvent but I’m not sure if my choice of solvent is a good one.
I'd think it was mostly nickel, but nickel oxide and most nickel salts are green. Some of cobalt's soluble compounds are red or pink, but it seems cobalt(II) oxide is black and I'm not sure if it has any insoluble compounds that match the magenta color.
Does anyone have any idea what this could be? I’ve attached a picture below.
Attachments
Last edited:
