Precious metal recovery/purification

[crazyboy25]

Precious metals are beautiful. Some have uses in chemistry, and some element collectors want samples or just to make their own. People can make a tidy profit off precious metal recovery, taking what others don't want and turning it into gold, silver, rhodium and platinum. Here I will show you a simple and easy way to extract and purify silver from sterling silver. This procedure is not likely to be profitable but it should work for most experiments.

 

 

First find some silver jewelry or silverware here I will be using old earrings. If you are using earrings or jewelry or anything else not made entirely of metal removal glue enamel copper or stones from your scarp as much as possible.

 

http://i179.photobucket.com/albums/w318/crazyboy25/002.jpg

My processed sterling silver.

 

 

Next if you are dealing with large items like plates or forks cut them, up so they fit in your beaker.

 

Pour enough 70% nitric acid in the beaker to just barely cover the silver. The clear acid may turn slightly yellow and the silver will tarnish. This is normal. If the mix instantly bubbles vigorously and spews large volumes of red gas the scrap you have is most likely NOT silver. If only a few places on the scrap bubble it is possible copper or other metal solder was used in making the scrap, this is fine.

 

Take your nitric acid solution with silver and gently heat it. The acid will bubble and will eventually begin releasing little bubbles of red gas about 30 seconds after the first bubble of gas or as soon as large volumes come over move the reaction outside or under a fume hood. The reddish gas is EXTEMLY TOXIC. The mix will bubble and the acid will turn a green hue as the silver metal is turned into silver nitrate and dissolved.

 

http://i179.photobucket.com/albums/w318/crazyboy25/004.jpg

The vigorous exothermic and toxic reaction takes place.

 

When the reaction subsides there may be undissolved silver. Take it and save it for later. Then add equal volume cold distilled water to the mix which should now be a blue color and filter it to remove the particulate matter.

 

http://i179.photobucket.com/albums/w318/crazyboy25/005.jpg

Filtering

 

 

Add about ten times the amount of water to this filtered mix as nitric acid you used at first. Then place a thick copper rod or plate into the mix. Silver will instantly begin to form on the copper rod.

 

http://i179.photobucket.com/albums/w318/crazyboy25/silver010.jpg

Silver forming on the copper rod

 

Allow the copper rod to sit in the solution until no more silver forms. Shake the copper rod the silver should fall off. Filter and wash the mix thoroughly this is your end result relatively pure silver metal free of glue, plastic, stones or copper.

 

http://i179.photobucket.com/albums/w318/crazyboy25/silver2002.jpg

 

 

 

Be careful, nitric acid is toxic and an irritant and silver nitrate is toxic and will stain everything it touches except glass. Always wear gloves and a respirator when performing this experiment.

[Sylar]

This would end up to be about 96-99,5% silver, depending on the other "crap" that was alloyed with it.

Basicly anything more noble then copper is deposited this way.

 

That said, there are cheaper ways to obtain Ag then jewelry.

A jewel maker, gold smith or bank will happily sell you technical or higher purity silver at a fraction of the cost of jewelry.

 

High power electrics (switches, relays/contactors) and even low power electronics are also a good source of cheap (and often high grade) precious metals. Processors have a gold coating over their pins, and thin pure gold wires to the chip internally.

Older >100KW contactors often contain over 10 grams pure silver soldered on copper bars. Newer types may use other alloys.

Car catalysts contain Pt.

[jacob]

Speaking of Catalytic converters, is there a reasonable hobbyist-level method to extract pure Pt from them? I imagine not but I figured I'd ask anyway.

[Mumbles]

I believe it would involve extracting the metal with Aqua Regia. I remember there being something about using cyanide, but that might be gold.

[Tweetybird88]

Pt can be extracted using Aqua Regia (or a mixture 1:3 I believe of nitric and hydrochloric acid) Its pretty easy to get the gold dissolved in this. Pt on the other hand requires a much longer process to extract the whole thing. I'm not positive on how to do it from there but I read up on all of this for the fake business I was starting for a business class at school.

[Miech]

Cyanide is used for gold and silver mining. Contaminations in gold and silver obtained this way are mercury, palladium and platina.

 

For extracting platina from catalytic converters you would need dozens of them for a single gram of platina. The obtained platina from extracting with aqua regia will not be pure, so some other redox reactions are needed as well.

 

Catalytic converters also are likely to contain palladium, rhodium, cerium, iron, manganese, nickel, copper and lanthanum. If pure platina is required, just buying might be a better way to get it.

[tentacles]

Rhodium is generally found in higher concentrations in older converters, before the precious metals "boom" (money grab). It was cheaper than Pt at the time and more effective in a CC, but now it's over $6k an ounce! It was under $700 an ounce like 10 years ago.

 

Anyways, I believe what you need to dissolve Pt group metals in AR is to heat the AR to near boiling. Not a very pleasant afternoon, all considered. I've got a couple hunks of CC I was going to play with someday when I can work outside.

[Arthur]

There are methods of recovering silver from photographic fixer and bleach=-fix. A good working lab should put out fix or blix at 3 - 5 grammes per litre. Simple ion exchange in a tub of steel wool will recover this down to 0,1 g/l if done slowly. When the whole tub of wire wool has collapsed into a silver sludge then simply raise the whole thing in a crucible to 1100c approx and the crud burns off or floats or sinks and you can flux loads of silver out - by the kilo.

 

I'm sure that the metalurgy of winning precious metals will be easily found if you get to a university library where the have a suitable course. Go in vacation to be there when more books are ion the shelves. UK Unis will let people read on site but only members may borrow books.

 

Most commercial recovery is done by complex ion formation using special compounds made specifically for particular separations. Recovering commercial quantities requires you to find huge quantities of the scrap/ore AND have the facilities to supply the product in ingot form with independently certified analysis. No-one is going to buy gold if it is in dust and some purity between 90 and 99.999% -- You would have to produce ingots of known weight of specified assay both to four or five figures.

 

For everything you plan consider the effluent - for every efluent there is a disposal cost.

[tentacles]

Refining the silver from silver nitrate solution is also VERY easy, much easier than reducing with copper. Just precipitate as chloride using table salt (cheap!) and then filter off the white fluff.

 

Rinse the silver chloride with water several times and then put in a solution of NaOH and sugar. Heat. The silver will precipitate out at a high purity, just decant and rinse several times.

[crazyboy25]

There are methods of recovering silver from photographic fixer and bleach=-fix.

Thats what I'm doing Friday my friends mom works at a veterinary hospital so he gets pounds of free X-rays I'll try to post a writeup if it works

 

 

Refining the silver from silver nitrate solution is also VERY easy, much easier than reducing with copper. Just precipitate as chloride using table salt (cheap!) and then filter off the white fluff.

 

Rinse the silver chloride with water several times and then put in a solution of NaOH and sugar. Heat. The silver will precipitate out at a high purity, just decant and rinse several times.

 

 

Silver nitrate to silver is easier and less toxic plus it doesn't require sodium hydroxide.

[tentacles]

Yeah but the end solution of sodium nitrate and (sugar?) is MUCH easier to dispose of than copper nitrate (which has it's uses too but questionable purity).

 

The sugar/hydroxide reduction is said to get close to three nines fine in a single step if you use distilled water for the rinsing.