Gold sponge with palladium contamination

[huggybear]

Hi All,

I have an aqua regia solution containing 10% gold and 0.1% palladium as well as 2% copper and some other base metals.

Once I deNox the solution and drop the gold using sodium sulfite, I am getting about 3000ppm of palladium in my gold sponge.

I have tried leaching the palladium from the gold sponge using nitric and hydrochloric acid washes but it only drops the palladium to around 1000ppm.

I am wondering if there's a better way to wash the sponge or if I can somehow avoid co-precipitating the palladium with my gold sponge.

Thanks,
huggy

 

[orvi]

It was discussed here some time ago, that with PGM contamined Au feed, it is better to drop the gold with FeSO4.

I never had problem with persistent Pd contamination of gold - but I always had these two together from processing AuPd pins, directly dissolved in AR. I dropped the gold with sulfite, and then precipitate Pd with DMG.

Then, I re-refined the gold also with sulfite (or better SO2 gas) and obtained 999Au, with Pd content about 0,03%. For me, this was more than sufficient.

 

[huggybear]

It was discussed here some time ago, that with PGM contamined Au feed, it is better to drop the gold with FeSO4.

I never had problem with persistent Pd contamination of gold - but I always had these two together from processing AuPd pins, directly dissolved in AR. I dropped the gold with sulfite, and then precipitate Pd with DMG.

Then, I re-refined the gold also with sulfite (or better SO2 gas) and obtained 999Au, with Pd content about 0,03%. For me, this was more than sufficient.

I remember wondering why some used FeSO4 instead of sulfite but that makes sense, I read it in a PGM refining chapter. I'll give it a shot.

If not you just re-refine.. by that you mean re-digest and precipitate?

Thanks

 

[orvi]

I remember wondering why some used FeSO4 instead of sulfite but that makes sense, I read it in a PGM refining chapter. I'll give it a shot.

If not you just re-refine.. by that you mean re-digest and precipitate?

Thanks

Yes. First drop is washed with bit of HCL, digested in AR and then re-precipitated.