Eco-goldex CYANIDE Leach

[patnor1011]

From all different batches there were only few pieces with undissolved gold. I simply picked them and included them to next batch of material and they were stripped.
When I finished I had only clean metal with all gold dissolved.

Pat, it looks like the stuff is doing a good job. When you get to find out about recovering the gold from the solution see if you can find out if the solution can be reused over again or if it is just a one time usage deal. Also if you would ask if it can be used for the recovery of other PGM's.

Will the solution attack copper or other base metals and id there a possability that the precious metals will cement back onto the base metals.

Thanks for doing this and keep up the good work.

This is only me thinking loud but I was told that activated carbon will suck out gold from solution. If solution will be reusable after carbon treatment I do not know but I am not very much concerned by possible reuse. He is selling 400g sample bags. According to him 400g bag can dissolve about 1 kilogram of gold. I did quite a bunch of material and all of this with about 500ml of water and about 5-7g of leach powder. I cleaned material with spray bottle and at the end I had about 1l of solution which is still working, I just tested it on another piece of material.
I suspect I can do another bunch of material with that 1l. According to him powder work on gold and silver.
So as far so good and I can say that only small bit of it will do quite a lot of material and price of powder is negligible compared to other chemicals or methods available. It may be a good idea to organize some group buy and then price can be even smaller.

I do not want to encourage anyone to buy that leach and use it to all of their material. I mean not till we figure out how to finish whole process. I did quite a lot of samples of various material and first I need to be able to hold that gold in hand. I estimate that I should have at least a gram of gold in there.

Solution will attack copper furiously as I have found out in my first attempt. Result was some powder on the bottom, clean stripped fingers (first picture first 4 fingers mostly clean stripped from all metal, while other 3 fingers and on my other pictures you can see nickel barrier still there) and solution turned deep dark green. This happen because Ph was too low. Around 7-8. I did used paper to measure it and color was dark green. My next batches which I posted pictures from I kept Ph at 11, color deep dark blue and only gold dissolved, not even nickel was attacked and exposed copper looked still like copper.

I need to figure out how to test solution for presence of gold. He suggest that when solution is loaded with gold stannous show it as blue stain, I tried stannous but my solution is just pale yellow and not much of a reaction when tested with stannous. I made stannous from water and anhydrous tin oxide, I did not wanted to use HCl on leach solution due to obvious concern with K3Fe(CN)6 presence even that it is small.
There must be something resembling cementation going on. I have started with clear solution with leach powder completely dissolved and ended up with blackish powder on bottom when settled. I suspect gold will be there. I am now trying to figure out what to do with this powder.

 

[g_axelsson]

A very interesting thread, thanks Pat!

As with all chemicals we use we should check the MSDS for it. [1]
As "Hazardous Reactions" only "Contact with acids liberates very toxic gas." is listed and among toxic products are hydrogen cyanide. It suggests that just as with cyanide, any acids should be kept far away.

As for toxicity, it is a lot less dangerous than potassium cyanide, LD50 is 3.6 g/kg [1] compared to 7.5 mg/kg [2] for potassium cyanide, a difference of 500 times less toxic.
The risk of harm from accidental transfer via fingers or dust is a lot better than with straight cyanide.

If the end result from Eco-goldex leach is the same as with cyanide, a cyanide gold complex, then the gold should be possible to recover in the same way as with cyanide. For example by cementation with zinc or electrowinning via Deano's carbon felt cell.

Eagerly waiting for the next installment in this thread. Will he be able to get his gold back? 8)

[1] https://www.fishersci.com/shop/msdsproxy?productName=AC211095000 MSDS Potassium ferrocyanide trihydrate
[2] https://www.fishersci.com/shop/msdsproxy?productName=P223I100 MSDS Potassium cyanide

Stay safe!

Göran

 

[g_axelsson]

Shouldn't this be red?

The K3Fe(CN)6 in my sons crystal growing kit is red. When mixed with water still red.

Eric

Might have to try it for fun.

I had to do some googling for this... 8)
The red crystals are potassium ferricyanide ( https://en.wikipedia.org/wiki/Potassium_ferricyanide ) not potassium ferrocyanide ( https://en.wikipedia.org/wiki/Potassium_ferrocyanide ).

Another good example of how important spelling is in chemistry.

Göran

 

[patnor1011]

I do need to order some more reagents like activated charcoal, that should come soon and powdered zinc. I only found some bits of zinc but I do not have any powder.
I tried to cut some small pieces of zinc, placed them in small 5ml bottle and put in some pregnant leach. Overnight they become covered with black residue. There is also some fine black powder particles on bottom. I tried to scrape zinc to make smallest possible dust and did the same. I will see if there will be the same reaction.
I would love to see Deano back, I would love to get some advice from him.

 

[upcyclist]

I only found some bits of zinc but I do not have any powder.

Darn, I wish you were stateside--I'd just throw some powder at you in the mail.

 

[Barren Realms 007]

I do need to order some more reagents like activated charcoal, that should come soon and powdered zinc. I only found some bits of zinc but I do not have any powder.
I tried to cut some small pieces of zinc, placed them in small 5ml bottle and put in some pregnant leach. Overnight they become covered with black residue. There is also some fine black powder particles on bottom. I tried to scrape zinc to make smallest possible dust and did the same. I will see if there will be the same reaction.
I would love to see Deano back, I would love to get some advice from him.

I think Deano still has a few weeks till he get's back.

Might try some air circulating the solution or put it on a stir plate with the solid zinc.

 

[patnor1011]

Perhaps I should have wait till I will have all of this cracked. I was bit impatient and now everyone must wait :mrgreen:
I ordered some coconut shell carbon but it is been 3 weeks and still no show, postman is getting allergic off me asking him every day about package from Philippines.
My zinc powder is also on route and form Ukraine so it also take few more days.
And to make matters worse I just found that I did not closed container with smb so now I do have yellowish block of something inside container. I like to work with "fresh" ingrediences so I just ordered new.

It is no problem, that dissolved gold is not going anywhere.

I am also up to neck in processing several buckets worth of backlog of IC's which I incinerated during winter. I am pedantic and slow and I like to have silicone cores removed, they take heavy toll on my pans when broken to small pieces. I do not want to even start about small BGA IC from RAM, they all do have pieces of fabric inside which I am removing too as when I crush them that fabric break and form small bundles. Sorry for morning rant...

 

[kazamir]

I believe this leaching reagent has eluded the small refiner.

If this is the case it means larger quantities of e scrap will be processed which may cause a shortage for large e scrap buyers like Boardsort and a price increase for e scrap.

I recommend that members hang on to even their marginal e scrap until Patnor and others inform us of their results.

Eco-goldex reagent is selling for 2850.00 USD per ton. but it is difficult to contact them.

 

[etack]

Shouldn't this be red?

The K3Fe(CN)6 in my sons crystal growing kit is red. When mixed with water still red.

Eric

Might have to try it for fun.

I had to do some googling for this... 8)
The red crystals are potassium ferricyanide ( https://en.wikipedia.org/wiki/Potassium_ferricyanide ) not potassium ferrocyanide ( https://en.wikipedia.org/wiki/Potassium_ferrocyanide ).

Another good example of how important spelling is in chemistry.

Göran

Cool I just cut and searched off of GSP MSDS he listed for this material.

He had K3 not K4

Their MSDS - in percent

NaOH ---------------------------------5-10
CO(NH2)3 = Urea--------------------15-30
NaCO3---------------------------------5-10
CaO------------------------------------20
K3Fe(CN)6.10H2O--------------------5-30
Na2SO4--------------------------------2-10
NaBr------------------------------------5-10

_________________
GoldSilverPro's eBook For Sale. viewtopic.php?f=84&t=22327&p=233617#p233617
________________________
"The refiner is always the last liar." Louis Labash, 1979
________________________

You are correct about spellings and numbers!!!

Eric

 

[FrugalRefiner]

The error is understandable. Even on the Eco-goldex web site, they mention on the Product page:

Reagent Major Chemical Compositions: This is a modified lime sulfur synthetic solution (MLSSS) reagent. The main ingredients include: LSSS, stabilizer (Sodium hexametaphosphate); oxidants (calcium peroxide and potassium ferricyanide); and additive (Sodium bromide, potassium bromide).

but later on the page they say:

Reagent Major Chemical Compositions: This low toxic eco-friendly gold leaching reagent consists of the following major chemicals: Urea, sodium hydroxide, sodium sulfate, Ammonium bicarbonate, sodium (potassium) ferrocyanide.

According to wikipedia:

Ferrocyanide may undergo oxidation, resulting in ferricyanide:
[Fe(CN)6]4− ⇌ [Fe(CN)6]3− + e−

Dave

 

[10wt_Percent]

EcoGoldex stripped audio connectors





concurrently-forming black precipitate





I found reagent consumption to be "nominal" .. it took a 400g. bag of ECO-Goldy to strip the audio
connectors as seen in the top pic. And to generate that black precipitate took two bags (as there
were more connectors than pictured .. twice as much).

All told: about 18 grams of dry black precipitate and around 6 litres of "apple juice" pregnant leach and around 3.5 kg of (deplated) audio jacks -- requiring 2 x 400g of EcoGdlx and around 14 days for digestion.

 

[patnor1011]

Just noticed your post, consumption looks too high. I did about a kilogram of gold plated material and about 300g of fingers and I did it in about 10g of powder. And out of it 5g (first batch) was turned bad as it had only about 7-8 ph so it attacked copper and turned green on about 150g of fingers.
I stripped all the rest I mentioned with just 5g of reagent and 1l of water.

 

[10wt_Percent]

I found (that) in order to continue to generate black precipitate it necessitated the addition of 10 gram allotments of Eco. This would "turn-over" in 24 hrs .. generating (additional) black precipitate and necessitating the addition of another 10 gram "shot" of Eco-in-water. The stuff "goes pretty quick" is my
experience with reasonably-aggressive "deplate-ment" of audio jacks. It's my impression (that) I was
operating in a "rate-limiting" regime. I found that in the case of the presumably more-heavily plated audio
jack style connectors; I had to "milk" the plating off with progressive additions (of EcoX).

Progressive additions of GoldeX and intermediate "decantings" to recover the black precipitate

Decanting to consist of swirling the leach/feedstock bucket; to encourage black precip into suspension ..
then pour off (all) liquid into settling vessel .. allow to settle 15 minutes .. pour liquid back into primary
leach pot .. all of it except for the last little bit -- containing the black precipitate. Add fresh Goldex to
leach pot .. repeat ^^ as required .. occasional swirling of the leach pot provides an indication of how much black precipitate has formed .. i.e. is it time to transfer .. time to add more Goldex? You soon develop an eye for how things are progressing.

Patnor, perhaps it's about plating thickness .. all my runs have been on plated lugs and audio connectors.

I really can't imagine getting by with much less consumption .. it kinda appears to "grind to a halt" (pretty
quickly) if I don't keep topping up on the Goldex (and continue to remove the accumulated precipitate.)

Trust this makes sense. We encourage questions and comments! 8)

 

[kazamir]

I don't expect any answers now but here are some questions for thought.

Is there an effect on plastics in the eco-goldex solution?
Is there a reaction to steel [ like Geo's concrete mixer]?
Does eco-goldex dissolve tin.?
Can silver also be deplated?

 

[patnor1011]

Perhaps it was working faster with less concentrated leach on my side because I used fish tank bubbler. Dunno but it might be it.

Is there an effect on plastics in the eco-goldex solution? Didn't try that yet.
Is there a reaction to steel [ like Geo's concrete mixer]? Dont think so, all material I tried appear intact just gold stripped
Does eco-goldex dissolve tin.? It does attack other metals if ph is not optimal 9-12. I got less and now I do have green solution, that was first batch where everything was stripped off fingers. Tin, nickel, gold, copper... all of it
Can silver also be deplated? It should. I will try some keyboard mylars next week. Have no clue where or how that silver present itself when/if stripped, I will try filtered leach without any solid particle.

 

[goldsilverpro]

In their literature, it mentions using SMB to reclaim the gold. Anyone tried it?

 

[10wt_Percent]

Is there an effect on plastics in the eco-goldex solution?
Is there a reaction to steel [ like Geo's concrete mixer]?
Does eco-goldex dissolve tin.?
Can silver also be deplated?

plastic is affected by the caustic nature of the EcoGoldeX solution .. it (the plastic) basically slowly begins to breakdown. You see this "degenerate plastic" floating around ... it's easy to sieve out (thankfully) .. just pour solution through aquarium-style fish net and you are good to go!

are there any adverse effects associated with the presence of iron and iron alloys? I'm not 100% sure - to be honest! The literature suggests EcoGoldex as useful for (the) stripping of rough e-scrap feed. This would seem to suggest no adverse effects due to presence of iron. I guess the test would be to run side by side leach tests .. otherwise identical "setups" -- except one "test stand" has steel wool added to the mix. See how things compare from the deplating perspective.

I found header-style pins much more reluctant to deplate than the more "monolithic" plated audio style connectors. Not sure why. I employed what I considered a pretty potent mix of pH adjusted (11.25)
EcoGoldex - No response for 10 days and then slowly it deplated (and not particularly thoroughly).

^^ it would stand to reason (that) header pins would be the test-feed of choice for assessing the viability (and variability) of the EcoGoldex strategy. i.e. figure out how to best strip header pins and you are on the right road (to riches)!

Time-lapse videography might shed some light on the otherwise interminably slow reaction kinetics. i.e. get a better fix on gestation periods and "reaction cycles".

I'd take this opportunity to stress the importance of good housekeeping i.e. keeping similar stock together .. (remove "freak" feedstock that may have responded (deplated) very quickly). Having deplated pieces loiter in the leach pot promotes cloudyness (as does leaving stock uncovered by leach for too long during "de
cantation"). I believe this is due to the formation of various metallic hydroxides. These are probably deleterious to Au dissolution.

Hope this helps .. it can be tricky to get (and keep) all things firing on all cylinders .. but through good house-keeping practice; things should stay reasonably-readily on-course. Happy trails!

8)

 

[Deano]

Potassium ferrocyanide will disassociate in solution to form ferrocyanide complexes, these complexes will decompose to form free cyanide.

Effectively what you are doing is running a cyanide leach where the cyanide concentration is controlled by pH, temperature and UV level.

If you have a cyanide probe you can optimise the conditions to get the maximum free cyanide in solution for leaching.

If you get the conditions wrong you will precipitate out cyanide-metal salts.

If you block out all UV light there is minimal decomposition of the ferrocyanide complex and virtually no free cyanide is formed.

Effectively you are performing a cyanide leach but using a much more intricate method of producing the cyanide complex than just dissolving straight sodium or calcium cyanide in water.

If what you want to do is to use this leach to dissolve gold the question is why would you use the more difficult route rather than just use straight cyanide.

Note that when you precipitate out cyanide - metal salts you will co-precipitate gold cyanide complexes.

By starting with the ferrocyanide complexes you are giving the leach the best conditions for precipitation to occur.

Any gold cyanide complexes in solution will respond to the traditional recovery methods of activated carbon and zinc etc.

Deano

 

[Platdigger]

Thank you Sir! I, as well as others have been waiting for your input on this.

 

[patnor1011]

Indeed, we are very grateful for your insight and opinion.