Eco-goldex CYANIDE Leach

[frank-20011]

hello,

i hope the low concentration of the gold was the reason...normally zincing out shouldn't be a problem.
but i think, in 100g of fully and partially plated stuff should be min. 50mg of Au and these Au in max. 200ml of water, is there really NOTHING when you try to dissolve and drop it out of these 200ml?
what do YOU MEAN about this calculus?

a stannous test was negative. i take one drop, only one drop of the pregnant sollution, add 1...than 2...than 3 and finally 4 drops of conc. stannous (the drop of the test-soll. was placed on a bottom of a white plastic beaker) but nothing, it stay's clear and colorless like tap water.


i make some tests in the past where i dissolve only a few bonding wires in a test tube with Hcl and one drop of HNO3...the resulting sollution changed clearly and promt the color after adding PMP but truly: this time it was more diluted.

one strange thing more about EG is: one time you can read at their web site zincing out is the way to do and activated coal isn't to prefere, on an other patch at their site they've wrote you CAN use activated coal and they also linked a video?????

i have had some success with Al-foil in a very!!! diluted sollution of commercial potassiumgoldcyanide (maybe you remember, i've found almost 100 plastic bottles in the waste of a plating shop where prior cristallic PGC was stored, a flush the bottles an get the gold with Al-foil) but at this time, in one case i add to the Zn-powder al-foil nothing to see, foil stay shiny.

one more strange point about the preparation of the pregnant EG sollution, the step before zincing out:

you can use NH3 to make sollution alkaline (like you do it with a standard cyanide-gold-leaching-sollution or, in the case you couln't buy NH3 in your country, you can use the reagents A, B and C TOGETHER to prepare the EG-sollution for the zincing process.

A, B and C consists of:

"Chemical A: Citric Acid, CAS No: 77-92-9
Chemical B: Ammonia Fluoride, CAS No: 12125-01-8
Chemical C: Magnesium Sulfate, CAS No: 7487-88-9"

AHA, a sulfate, a flouride and an organic acid to prepare the pregnant sollution for zincing out PM....

but: " NEVER add eco-golde reagent into ACID solution as this will generate hazard gases (S2O3 + H+ ->SO2(gas) + S)."

no word about HCN.

best regards, frank!

 

[Platdigger]

OK guys, I googled K3Fe(cn)6 and I come up with it being Potassium ferricyanide.
Ferri
It turns out that Ferro is K4.....
Actually K4[Fe(CN)6] 3H2O
So evidently this stuff uses Ferri not Ferro.
Right?

 

[frank-20011]

hello,

yes, i have had make these mistake often but for the process it make no big difference: when heating ferro or ferri you get cyanide (and iron) especeally under an inert atmosphere, there is loooong tread at the smd forum.

best regards!

 

[kurtak]

one strange thing more about EG is: one time you can read at their web site zincing out is the way to do and activated coal isn't to prefere, on an other patch at their site they've wrote you CAN use activated coal and they also linked a video?????

one more strange point about the preparation of the pregnant EG sollution, the step before zincing out:

you can use NH3 to make sollution alkaline (like you do it with a standard cyanide-gold-leaching-sollution or, in the case you couln't buy NH3 in your country, you can use the reagents A, B and C TOGETHER to prepare the EG-sollution for the zincing process.

best regards, frank!

Frank

First of all concerning the instructions of the Eco-Goldex product I assume you are talking about the instructions here

:arrow: http://eco-friendly-gold-leaching.com/index.php

The confusion over them saying in one place that recovery of the gold from the pregnant EG solution with activated carbon "does not" work - & then in another place recovery with activated carbon does work - is because they are talking about 2 different EG products (I think they actually have 3 different products)

One (or 2) product(s) is a product(s) they recommend for leaching ore - this product(s) they claim activated carbon will work to recover the gold from solution

The other product (which they call the E-series Eco-Goldex) is recommended for stripping/leaching gold plating from electronic scrap (ie. gold plated pins, fingers etc.)

It is this "E-series" product which activated carbon "will NOT work" to recover your gold from solution !!!

Also - when talking about their E-series product - adding the NH3 has nothing to do with "adjusting the pH"

The NH3 MUST be added to the pregnant solution in order to cement the gold from solution with zinc (or aluminum) --- with out the addition of the NH3 - the gold will NOT cement out of solution when you add the zinc or aluminum --- if you can't get NH3 - then - instead you can use the addition of the A/B/C chemicals

The addition of ether NH3 - or - chemicals A/B/C is done AFTER leaching the gold & BEFORE cementing the gold !

It should be noted here that you pretty much need to use 29.5% "industrial" NH3 for this --- you can get away with off the shelf "household" NH3 - BUT - because household NH3 only tends to run about 3% you have to add a LOT more so you end up diluting you leach solution WAY down which in turn results in increasing your waste BY A LOT --- you MUST have GOOD fume control when working with "industrial" NH3 - working outside with the wind at your back "is NOT good enough"

So - it depends on which one of their products you are talking about as to whether or NOT activated carbon will work to recover your gold or NOT

As best as I can tell - they have 3 products - they are

Thiosulfate Gold Leaching Reagent

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).

Gold Dissolving Mechanism: The effective components that leaching gold include sulfite, thiosulfate and polysulfide. Chemical reactions of gold dissolution can be generalized as:

2Au + 2Sx2-+H2O+1/2O2 → 2AuS+2OH-  +2(X-1)S
2Au＋4S2032-＋ 1/202＋2H20 → 2Au(S2O3）23-＋20H-

Thiourea Gold Leaching Reagent

Reagent Major Chemical Compositions: major components forming Thiourea gold leaching reagent include: Alkaline Thiourea, stabilizer ( sodium hexametaphosphate or trisodium phosphate), Oxidant (Calcium peroxide), additive (EDTA).

Gold Dissolving Mechanism: Chemical reactions of gold dissolution in Alkaline thiourea can be generalized as:

S2O 82- +2Au+4CS(NH2)2=2Au[CS(NH2)2]2+ +2SO4 2-
O2+4Au+8CS(NH2)2+2H2O=4Au[CS(NH2)2]2+ +4OH-

Low-Toxic Eco-friendly Gold Leaching Reagent (this is the "E-series" product)

Reagent Major Chemical Compositions: This low toxic eco-friendly gold leaching reagent consists of the following major chemicals: Urea, sodium hydroxide, sodium sulfate, Ammonia bicarbonate, sodium ferrocyanide. These chemicals are mixed with predefined proportion and melted in reactor under 650-850 oC, after cooled down, the material is grind and mixed with bromide to form the final leaching reagent. Different producers may change their chemical receipts slightly and accordingly demonstrate different leaching strength or ore type adapting features.

Gold Dissolving Mechanism: Though the complete gold dissolving mechanism of this group gold leaching reagent has yet fully understood, at least three of the following reactions exist in the process of gold leaching:

Au+2NH3=Au(NH3)2+
Au+4NH3=Au(NH3)43+
Au+[Fe(CN6)]3- + O2--> [Au(CN)4]3- + Fe3+

This (the E-series) IS "cyanide" --- in fact they say "in red letters" ------- "What makes Eco-Goldex successfully accepted in commercial production is that it is a simple system, which has exactly the same operational procedures and conditions as cyanidation. It is easy to use and can seamlessly replace sodium cyanide in most gold leaching operations

Kurt

 

[anachronism]

I'd be really interested to see why the E series one that "is cyanide" will not allow you to use activate carbon.

 

[kurtak]

I'd be really interested to see why the E series one that "is cyanide" will not allow you to use activate carbon.

Jon

I am no chemist so I can't say for sure - but - I "suspect" that it has something to do with the Ammonia bicarbonate being "one" of the ingredients in the E-series EG

according to Wiki - Ammonia bicarbonate - when reacted with bases - produces ammonia - the EG (Eco-Goldex) product is a basic (as in "a base" - ie. NaOH) product

Again - according to the info from EG - they say -----

Gold Dissolving Mechanism: Though the complete gold dissolving mechanism of this group gold leaching reagent has yet fully understood, at least three of the following reactions exist in the process of gold leaching:

Au+2NH3=Au(NH3)2+
Au+4NH3=Au(NH3)43+
Au+[Fe(CN6)]3- + O2--> [Au(CN)4]3- + Fe3+

so according to that we are seeing three different (possible) gold complexes - the CN complex - but also Au(NH3)2+ which is a diamine complex - and Au(NH3)43+ which is a tetraammine complex --- meaning an ammine(2) &/or an ammine(3) gold complex

So I "assume/suspect" it is these ammine complex(s) that prevent the gold from reducing with activated carbon

It is also I "assume/suspect" why more ammonia has to be added in order for the cementing with zinc/aluminum to work - the assumption being the E-series EG product does not provide enough NH3 on its own to facilitate metal ion exchange of the ammine complex(s) - &/or something (else) in the mix is buffering the E-series from facilitating the metal ion exchange --- so ammonia has to be "added" to facilitate metal ion exchange

As I say - I don't really know - & so assume --- What I do know - is that they (EG) has two sets of instructions for their products --- one set of instructions for the E-series product - & another set of instructions for the other two products (which they refer to as Eco-Goldex O/C Reagent)

In the E-series instructions they specifically state - "It has been confirmed that Activated Carbon is NOT a good candidate to recover gold from Eco-goldex E series product derived pregnant solution."

Where as in the O/C Reagent instructions they say ether activated carbon or zinc will work to recover the gold

The bottom line - regardless of what is actually going on in the chemistry here - is that though the E-series product does work for leaching gold from electronic scrap - it is nothing short of a real pain in the butt when it comes to the recovery of the gold from the product --- working with "concentrated" ammonia is NOT my idea of fun

Kurt

 

[frank-20011]

hello,

"I am no chemist so I can't say for sure - but - I "suspect" that it has something to do with the Ammonia bicarbonate being "one" of the ingredients in the E-series EG"

but NH4HCO3 isn't longer itself if it's heated above 58°C ( NH4HCO3reagiert zu NH3 + CO2 + H2O) and we remember:

"These chemicals*** are mixed with predefined proportion and melted in reactor under 650-850 oC, after cooled down, the material is grind and mixed with bromide to form the final leaching reagent. Different producers may change their chemical"

***these chemiacals: the content of EG (not shure about the type of EG) is counted by the msds, NH4HCO3 is listed on an other passage at their web site.

regards, frank!

 

[Rreyes097]

So am i understanding this whole thread right? That no one has been able to successfully precipitate their gold out of solution yet?

 

[kurtak]

So am i understanding this whole thread right? That no one has been able to successfully precipitate their gold out of solution yet?

No - it has been figured out - the gold is recovered from solution by cementing with zinc or aluminum

BUT - in order for the cementing to work you FIRST need to add ether ammonia to the solution - OR - what Eco-Goldex refers to as chemicals A, B & C

Chemicals A, B & C are ---------

A) Citric Acid,
B) Ammonia Fluoride
C) Magnesium Sulfate

If you go up & read the post (on this page) by frank-20011 & then my reply you will see where we talk about this - here a quick link to the post (on this page) by frank-20011 - read his post & my reply

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=23843&start=180#p267242

Also here is a link to a thread I posted about it

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=25001&p=264655#p264532

Kurt

 

[Rreyes097]

I thought I've seen somewhere in this thread on how much of this E-series eco-goldex to use in how much water? I believe I seen 1 litter of water to 100 grams? Please advise.

 

[anachronism]

If you have bought it are the instructions with it?

 

[Rreyes097]

I have bought it but no instructions come with it although there is a PDF that you can download that shows you how to do it but I don't believe it gives an amount of what to use. Patnor1011 i believe was the one that mentioned using about 10 grams of the eco-goldex but im not sure if he was using the older version or the newer version that doesn't require ph monitoring. Or if there is even a difference. But i went ahead and started with 10 grams and it's seems to be working well. On gold fingers, gold plated jewelry, green boards from cell phones, pinless cpus (these took a little longer) and even a gold filled ring!(took awhile but it got it done!) There isn't any visible change in the solution but still remains strong as ever. Its sitting on a hot plate that has a magnetic stirrer which seems to bring out the best of the eco-goldex. Im just worried about the ammonia in going to be using. If it's going to work to help precipitate the gold since it's only standard and not industrial strength. Anyone successfully get their gold to precipitate using this ammonia? If so did you use aluminum or zinc?

 

[Rreyes097]

Well stripping went well. But perciptating didn't go well. Used 64ozs of regular store bought ammonia. Which is well over needed amount. I calculated it needed roughly 1200 ml approximately. 50 grams of zinc strips. I think im over estimating that there is 5 grams of gold. No reaction after both were added. Anyone think I've messed it all up out think i can simply get industrial strength ammonia and be good to go?

 

[Rreyes097]

I need help recovering my gold! Anyone able to guide me?

 

[Rreyes097]

I just wanted to uodate everyone on my experience with this product. I did a test run with this product. My trial run included 3-4 lbs of plated jewelry, cell phone boards, plated pins, heat speaders, and whatever else i could try. Well i didn't have the righr anmonia and things didn't go as planned and I've been trying to work with the owner or creator of eco-goldex john Guo he tried to give me advice but to no avail i still have let to get my gold! He then asked what kind of material and how much. I explained to him what i used and he told me that I've been wasting my time and his. But i honestly think he didn't have any knowledge on how to help me. Does anybody else think that little amount of gold is a waste of time? Especially being a trial run. Does anyone have the time to waste to help me recover my little bit of gold? Ive attached a pic of what i thought was my gold.

 

[frank-20011]

hello,

pfffff...4lbs of plated stuff, I! think, that isn't a waste of time especially for a hobbyist and especially with plated jemelry---right: i isn't much gold but as i stated: it is hobby!

is it really impossible to buy HN3 in the USA?
you can'r buy NH3 (aqueous, weak concentrations as a cleaning agent, propper concentretion in lab-commerce) or make your own in gaesous form?
it dissolves VERY easy in water.

What have you done to precipitate the gild till now-ony trials?

best regards, frank!

 

[Deano]

The easiest way to recover gold from these solutions is to contact the solution with activated carbon, ash the carbon and aqua regia digest the ash.

I use coarse activated carbon for ease of ashing, Pica 4 x 8 mesh, well washed.

Ashing is in porcelain dishes with 1 to 2 cm thick layers.

Ashing temp is 650C over night with good air access.

Deano

 

[kernels]

The easiest way to recover gold from these solutions is to contact the solution with activated carbon, ash the carbon and aqua regia digest the ash.

I use coarse activated carbon for ease of ashing, Pica 4 x 8 mesh, well washed.

Ashing is in porcelain dishes with 1 to 2 cm thick layers.

Ashing temp is 650C over night with good air access.

Deano

Hi Deano, in your other (excellent) thread you mention that you measure the gold content going into and out of your activated carbon container, and use that information to know when the carbon is saturated. How do you measure the amount of dissolved gold in the cyanide solution ? I assume for a small-scale home based guy like me the best bet is to just put way too much activated carbon in ?

 

[Deano]

I avoid most of the problems associated with specialty leaching reagents by just using straight cyanide.

If I wanted to use a ferrocyanide leach I would run it without any other reagents, just use dissolved oxygen from the air as your oxidant at pH 11.

I use AAS to measure the gold tenors in and out of a transparent plastic column containing a carbon charge 50mm diameter by 500mm long.

Flow rate is around 30ml/minute.

Most of my liquors have pretty high levels of base metals, especially copper, so the actual gold loadings are relatively low.

I would expect to get around 15 grams of gold on the carbon before any appreciable levels of gold appeared in the overflow.

I avoid stirring carbon in beakers as the attrition rate is high.

There is so much stuff in the Eco-goldex leach that anything but AAS gives pretty difficult to interpret results.

If you expect a solution to have 10 grams or less of gold then you can run it through the carbon and ash the carbon.

Pass the hopefully gold free used liquor through the next batch of carbon that you use as a scavenge run before passing the next batch of higher grade gold loaded liquor through the column.

Deano

 

[kurtak]

The easiest way to recover gold from these solutions is to contact the solution with activated carbon, ash the carbon and aqua regia digest the ash.

Deano

Deano

In the E-series instructions (from Eco-Goldex) they specifically state - "It has been confirmed that Activated Carbon is NOT a good candidate to recover gold from Eco-goldex E series product derived pregnant solution."

They have two other leach products that activated carbon will work with - but (according to them) it wont work with the "E-series" product

So that along with the fact that in order to cement the gold with zinc (or aluminum) you MUST add ammonia to the solution BEFORE cementing makes their E-series product a real pain in the butt

Though I have not tried it yet I think the best way to recover the gold from the E-series product is most likely going to be the flow through electro win cell you & Jon have posted about

Kurt