Removing gold

shanered

I hear there are elements of gold in old mobile phones, cpu's in laptops etc.
Has anybody removed these elements before?
Any general information and disscussion about this would be great!

Maximus Alexander

There is less than 1/20 of a gram of gold in a mobile phone, which has a value of about €1.80. The effort it would take to extract it wouldn't be remotely worth it unless you really don't value your time.

I wouldn't get too excited about it

krd

In places in India and Africa, people do recover the metals from electronics.

They literally cook the circuit boards up in chemicals, then take whatever they can get from the sludge. It's dirty and there wouldn't be much money in it.

j4vier

aqua regia can dissolve metals, often used it myself in the lab

haven't seen anything else that works as good to remove metals from surfaces

shanered

Aqua regia dissolves gold, though neither constituent acid will do so alone, because, in combination, each acid performs a different task. Nitric acid is a powerful oxidizer, which will actually dissolve a virtually undetectable amount of gold, forming gold ions (Au3+). The hydrochloric acid provides a ready supply of chloride ions (Cl−), which react with the gold ions to produce chloroaurate anions, also in solution. The reaction with hydrochloric acid is an equilibrium reaction which favors formation of chloroaurate anions (AuCl4−). This results in a removal of gold ions from solution and allows further oxidation of gold to take place. The gold dissolves to become chloroauric acid. In addition, gold may be dissolved by the free chlorine present in aqua regia. Appropriate equations are
Au (s) + 3 NO3− (aq) + 6 H+ (aq) → Au3+ (aq) + 3 NO2 (g) + 3 H2O (l) and
Au3+ (aq) + 4 Cl− (aq) → AuCl4− (aq).
The oxidation reaction can also be written with nitric oxide as the product rather than nitrogen dioxide:
Au (s) + NO3− (aq) + 4 H+ (aq) → Au3+ (aq) + NO (g) + 2 H2O (l).




I see this, what does it mean by the free chlorine? How is this done exactly?

shanered

krd wrote: »

In places in India and Africa, people do recover the metals from electronics.

They literally cook the circuit boards up in chemicals, then take whatever they can get from the sludge. It's dirty and there wouldn't be much money in it.

How do they take it from the sludge do you know?

krd

shanered wrote: »

How do they take it from the sludge do you know?

I've seen video of them doing this. It's a real dirty business that's done in backyards.

They start by literally burning the plastic off. Then they cook whatever they have in what's possibly Aqua Regia - which is just mixed acids.

Then next I would say they force the gold to precipitate, and decant their acid. Probably reuse it.

Then with the sludge, it might not be too difficult to refine the gold - neutralise it, and heat it, the gold probably forms nuggets.


The reason they do it in Africa and India, and we don't do it here, is the cost of getting rid of wastes. There, they're more or less pouring this stuff down the drain. Here you would not be allowed to do that. You'd have to have your waste treated or disposed, and that can be very expensive. So, it's probably more expensive to cook the gold out than bury the phone in a landfill.

shanered

I understand what your saying in regards to cost and benifit. And the enviormental issues.
I what to do this more as an experiment rather than make a living off it, but thanks for your concerns about my possibly wasted time.

Would Sodium Hydroxide neutralise it?

SOL

The real problem for disposal isn't the acid, it is the fact that you will have dissolved pretty much every bit of metal in whatever you are recovering it from (with few exceptions), and you are then pouring a mixture of heavy metals down the drain, electronics often contain lots of quite toxic heavy metals, so you'd have to remove those first.
Pouring a bottle of HCL and HNO3 down the drain, aside from the destruction it might do to the plumbing will have pretty negligable environmental impact. (Though it is still illegal, so dont do it.)

krd

SOL wrote: »

The real problem for disposal isn't the acid, it is the fact that you will have dissolved pretty much every bit of metal in whatever you are recovering it from (with few exceptions), and you are then pouring a mixture of heavy metals down the drain, electronics often contain lots of quite toxic heavy metals, so you'd have to remove those first.

Do you know what heavy metals are in electronics?


I've heard Intel use some radioactive material. Though I've never been able to understand what the use for radio actives in electronics would be - I would assume they'd make the circuits a little less predictable.

Pouring a bottle of HCL and HNO3 down the drain, aside from the destruction it might do to the plumbing will have pretty negligable environmental impact. (Though it is still illegal, so dont do it.)

When Intel first set up in Ireland, they were dumping their solvents straight into the nearby river/or stream - they were caught, but they were let off.

Generally, in developing world countries, you can get away with murder, when it comes to dumping.

I've of people running factories on ships sailing the Amazon - once you get a distance in, there's no one around to ask you what you think you're doing, with you sludge. Maybe a few indigenous people - but I think you're allowed shoot them.

shanered

I don't want to get too side tracked by enviormental issues, but I am glad you mentioned them. I realise that they need to be disposed of in a enviormentally aware fashion.