how to recover pd and silver

[wjbtd]

Dear all

I have a big problem to recover Pd and silver when deal with some special chips.

This kind of chip (you can see in picture 1) has 140g/t gold ,480g/t silver, 50g/t palldium and about 40% of copper.

My step to treat this kind of chip is as bleow
1. burning in the furnace (you can see the product after burning in picture 2)
2. Dissolving it in sulphric acid (150g/L) and adding H2O2 continuously （total 5L H2O2 /100L solution), keep the temperture between 50 to 60 ℃， at the end of the reaction. The copper content in the solution could reach 20 g/L.
And problem comes here, there is about 2ppm silver and 1ppm pd in the solution.
so there is 20kg copper ,2g silver, 1g palldium in 1m³ solution. which means about 10% of Ag and 40% of Pd will lost.
3. Putting the copper sulphate solution to electrowinning, and get cathode copper,and I found most of silver and palladium depositing in the cathode copper. In other words ,they gone with copper.
I analyse the cathode copper, about 100g/t Ag and 50 g/t Pd in the cathode copper.
4. We hope to recover Au ,Ag ,pd from the resuide after remoe the copper ,but most of pd and some Ag losted because of step 2.

Sp anyone have a better idea

 

[kjavanb123]

Hi,

If you can access nitric acid easily in your place, you can dissolve Pd, Ag and Cu in dilute nitric acid, filter press everything, incinerate the residue which going to hold your gold, then dissolve it in aqua regia, filter press and precipitate your gold.

Now with your Pd, Ag and Cu nitrate solution, add salt and filter the silver chloride, add DMG per instructions found on forum and filter the canary yellow Pd salt, you are left with mostly copper nitrate solution, which at last resort can hang two scrap iron sheets and plate the copper.

Regards
Kj

 

[nickvc]

Kevin I agree with the first part of your processing to convert the silver to chloride but the second step for me would be to cement the Pd with copper and recover the black powder for either melting or refining and the copper in solution can either be plated out or cemented out with iron whichever pays the best for the least effort or cost.

 

[4metals]

You guys are thinking refining methods for concentrates and the OP is talking ppm levels. This is a proposition for a resin to selectively remove the Pd and Ag from the solution right after the sulfuric digestion.

 

[Platdigger]

4metals, do you have a certain resin in mind for the pd?

 

[4metals]

Considering it is a sulfuric solution I would have to do a bit of research, not being in a place to do that for a few more days, I may have to beg a favor of Lou for a recommendation.

 

[wjbtd]

Thanks a lot for all your suggestions.

Use the nitric acid is not suitable for my process, there is 40% of copper in the chips, it will consume a lot of HNO3 and too much NOx. I use H2SO4 and H2O2 to lecah copper and the do electrowinning process, so the H2SO4 could use again.

I think to recover trace amount of pd is big problem for wet method.

If there is suitable resin for the sulphric solution, I wander to konw and hope could do some test.

 

[4metals]

wjbtd,

You reported me for not telling you how to do this? That is comical.

I happen to be away from my home office and can not look this information up while on the road. I apologize for not having committed all of the possible scenarios to memory.

I don't suppose you understand that recovering 1 part per 1,000,000 of Palladium from a sulfate solution that is saturated with copper is at best difficult. And this is PdSO₄ And the silver at 2 PPM is also a sulfate.

 

[g_axelsson]

How about a hot sulfuric leach with electrowinning of the copper. That would recreate the sulfuric acid for reuse while silver and palladium probably would follow the copper and concentrate. The leftover would be high in gold.

The silver can be reclaimed by controlled additions of chloride ions before electrowinning. Palladium can be reclaimed in resin.

If the leach goes directly to electrowinning then the silver and palladium will probably follow the copper but can be separated in a copper cell in a later stage.

The undissolved remnants after the leach should be a lot higher in gold and might be suitable for leaching with AR.

Another alternative is smelting the whole lot and making a refiners bar of mostly copper. That can be run through a copper cell and so on... See the recent smelting thread and copper cell thread for details.

Now... since you quoted numbers per ton everyone assumes you have tons, do you? If you only have kilos you might get other advice.

I assume the reported post was a mistake, basically the same text were posted in the thread too, so I removed the report.

Göran

 

[anachronism]

wjbtd,

You reported me for not telling you how to do this? That is comical.

I happen to be away from my home office and can not look this information up while on the road. I apologize for not having committed all of the possible scenarios to memory.

I don't suppose you understand that recovering 1 part per 1,000,000 of Palladium from a sulfate solution that is saturated with copper is at best difficult. And this is PdSO₄ And the silver at 2 PPM is also a sulfate.

To add to 4metals post if I may:

What would be the commercials of trying to recover 1ppm Pd from a solution? Realistically the costs are likely to outweigh the returns, so from a financial point of view do you think it is really worth it?

 

[g_axelsson]

I don't know where the 1 ppm Pd number comes from. The original poster mention 50g Pd per ton, to get to 1 ppm you need 50 cubic meters of sulfuric acid dissolving about 300 kg copper and some silver and palladium. To me it feels there is something wrong with the numbers, I would think a cubic meter should be enough for 300 kg copper or there about, making it more like 50 ppm after leaching. Dilution would make it lower of course since concentrated sulfuric might be too strong, but not down to 2%.

Göran

 

[anachronism]

2. Dissolving it in sulphric acid (150g/L) and adding H2O2 continuously （total 5L H2O2 /100L solution), keep the temperture between 50 to 60 ℃， at the end of the reaction. The copper content in the solution could reach 20 g/L.
And problem comes here, there is about 2ppm silver and 1ppm pd in the solution.
so there is 20kg copper ,2g silver, 1g palldium in 1m³ solution. which means about 10% of Ag and 40% of Pd will lost.

Goran it is from the original post. As above.

 

[g_axelsson]

To my defense I'm half blind on one eye at the moment (an eye infection).
My second eye have no defense...

I should have read the original post better.

Göran

 

[anachronism]

Hey it doesn't matter mate.

Tell your second eye to get with the programme.

 

[wjbtd]

Sorry for the late response.I was out for almost a week.

Yes ,i have 2 tons of this kind chips, and i'm a chemical engineer in a small precious metal recovery company in china.
Normally , we just deal with korat gold scraps, but some customer ask us to do this kind of chips.
We just have a incination furnace but donn't have smelting furnace like umicore, so we can not make copper alloy.
We want to use our existing equipment to cope with the chips and try to recovery as more as we can.
My factory have a ICP, so i can accurately test the solution.

If you consider the solution will circulate between leaching and electrowinning , and you will know a small lose will accumulate. Espacially when raw material just have a few precious metal,the recovery rate will drop dramatically.
Hopes in the future , china will build a smelter like boliden or umicore.

Since the customer agrees that Ag and pd is without charge , it's not so disturbing now.
And still thanks for all.

 

[saadat68]

Hi
Can someone say to me why starter doesn't cement silver and Pd with copper in step 2 ( After digesting in sulfuric acid ) ?