Thiosulphate Dropped--Testing for PM?

[Dr. Poe]

Ferrell; You can view my posts simply by typing "Dr. Poe" in the search box. Thiosulphate used to be (wrongly) called "hypo".
Photo labs recycle their "hypo" solutions through a bucket filled with plain steel wool. The gold , silver and PGM's were adsorbed onto the steel wool, cleaning the solution for reuse. Notice that I wrote "adsorbed" and not "absorbed". They then sold the bucket to people like me (us) to be smelted. It's quite easy to smelt gold from steel wool.
I hope this might help you. Dr. Poe :mrgreen:

 

[butcher]

Good thought Dr, POE, my concern is this Iron may be a sulfate, I would think elemental iron may be needed in melt, what do you think.

 

[Dr. Poe]

I'm sorry, I goofed. I should have read the post more carefully. It said that ferrous sulfate was used to drop the gold from the solution. It's true that I've seen gold powders of a mauve-red color thousands of times, but this time butcher is most likely right. Here's my notes from 20 years ago:
SODIUM GOLD THIOSULFATE (MONO-VALENT), Na3[Au(S2O3)2-2H2O
A solution of HAuCl4 is added slowly with constant stirring to a slight excess of sodium thiosulfate
solution. Some sulfur dioxide gas is liberated and a little sulfur separates. After filtering, Na3[Au(S2O3)2-2H2O is precipitated by addition of absolute alcohol. It is a colorless compound, very soluble in water, but insoluble in alcohol. It loses it's water of crystallization at 150-160C without decomposition. This complex is so stable that it is not reduced to metal by ferrous sulfate, SO2, or stannous chloride. It's very important to keep ammonia and acetylene (and map gas) away from this compound as
it will explode very violently! Recovery of the gold is made by soaking in a vessel of steel wool (not stainless). The gold is adsorbed onto the metallic iron/steel.
Again, I apologize, You will need to cupel a sample. Don't just wrap it in lead or bismuth. Start with the oxide of lead or bismuth. add iron/steel nails to the melt, then cupel the prill.
Dr. Poe

 

[samuel-a]

Dr. Poe

A solution of HAuCl4 is added slowly with constant stirring to a slight excess of sodium thiosulfate
solution. Some sulfur dioxide gas is liberated and a little sulfur separates. After filtering, Na3[Au(S2O3)2-2H2O is precipitated by addition of absolute alcohol. It is a colorless compound, very soluble in water, but insoluble in alcohol. It loses it's water of crystallization at 150-160C without decomposition. This complex is so stable that it is not reduced to metal by ferrous sulfate, SO2, or stannous chloride.

I don't follow you here, may you explain further...?


Is there a way to reduce metalic gold from thiosulfate leach?

 

[Dr. Poe]

Dr. Poe

A solution of HAuCl4 is added slowly with constant stirring to a slight excess of sodium thiosulfate
solution. Some sulfur dioxide gas is liberated and a little sulfur separates. After filtering, Na3[Au(S2O3)2-2H2O is precipitated by addition of absolute alcohol. It is a colorless compound, very soluble in water, but insoluble in alcohol. It loses it's water of crystallization at 150-160C without decomposition. This complex is so stable that it is not reduced to metal by ferrous sulfate, SO2, or stannous chloride.

I don't follow you here, may you explain further...?


Is there a way to reduce metalic gold from thiosulfate leach?

The Iron/steel wool. An iron, titanium nitride or stainless anode. This leach is able to leach gold from carbonaceous ores. God, uses this leach to bring gold up from the depths of the earth. The pressure on quartz veins produces a low voltage that reduces gold. If a reagent won't reduce gold to metallic from a cyanide solution, it surely won't from a thiosulfate leach as thiosulfate gold is more stable than the double alkali cyanide leach. Zinc chips work better than zinc powder, but finely divided iron (steel wool) works best. Gold in this leach is in a plus one state, but the complex over all is a negative charge. It decomposes on the anode. The presence in the chloride leaches for gold prevent precipitation and account for loses mostly from natural earth ores. You need almost 6 volts to electrowin or electroplate gold from thiosulfates (1.68 + 1.68 = 3.36 + 0.79 (hydrogen build up on the cathode) = 4.15 minimum; hence 6 volts DC is my recommendation. I don't like to use zinc in this situation due to formation of zinc sulfide.
I don't fiddle with them, steel wool is my method of choice. The sodium thiosulfate is then reusable.
It rejects iron. It's the differential voltage that makes the steel wool work. The total voltage, that is from a larger area of the steel wool. Sodium thiosulfate is great for difficult natural ores, but I don't like it for processing scrap.
Dr. Poe :|

 

[butcher]

Sulfide’s with gold, melting with iron, there is a chemical reaction in the melt (replacement reaction), the iron (I believe) makes iron sulfide (robbing the gold of the sulfide), Iron which will give off SO2 gas in melt easily, also converting some sulfide to sulfur that burns off as SO2 gas(where gold would not release this gas easily and may just melt as gold sulfide without any iron had been added to melt) once sulfur removed from iron it is most likely just rust Iron oxide absorbed into the slag, and gold reduced to metal in button (of coarse would need refining).

I do not know if this would be true of the gold retrieved as gold thiosulfate (gold sulfate compounds) but I am guessing it may be.

(This is what I believe happens; maybe someone can rephrase this to make more sense.)

Dr.Poe,
Great post, I have a question,

"The sodium thiosulfate is then reusable.
It rejects iron"


(Can you describe this in easy to understand terms) what I do not understand is:
Ok If I dissolved gold or silver in thio sulfate (Hypo), and used Iron to replace these metals in solution (to me this means the iron goes into solution as a thiosulfate compound plating or cementing out the gold or silver from solution).

My question is how the thiosulfate rejects iron easily (on its own or through another treatment), and if it rejects iron easy why would it not just precipitate this iron with the gold (although the melt would reject iron from gold I assume), I do not quite understand this.

 

[Ferrell]

I'm sorry, I goofed. I should have read the post more carefully. It said that ferrous sulfate was used to drop the gold from the solution. It's true that I've seen gold powders of a mauve-red color thousands of times, but this time butcher is most likely right.
Dr. Poe

Dr. Poe, just a quick note here that everyone seems to be missing on two of my posts: The mauve-red/gold color on the filter you're referring to, was a result of leaching pins that were copper covered with a thin layer of gold. NO iron or any other metal is contained in them, just copper and gold.

The OTHER pic of the filter that is light golden is from our ore. We've been told by a man who's spent years using thiosulphate leach, that iron will not interfere with this leach or go into solution as long as the ph is kept above 9.0 when leaching (which we did), or the leach is allowed to sit too long (which we didn't).

Also, we did tests on this same ore using SSN, butyl diglyme, and oxalic acid, and captured/dropped gold, not iron. Butyl will not capture anything other than gold, so we know (when we did those tests) that we didn't drop any iron. If there's too much copper in the ore/solution, the butyl will turn milky, and our solution has never done so.

 

[butcher]

Copper is easily dissolved from gold.
If just gold and copper in sulfate form (thiosulfates), roasting to drive off sulfate as SO2 gas (roast red hot, Iron nails in roast would possibly be good idea also), then dissolve copper (iron) with one of many methods available on forum (HCL/H2O2, or nitric acid, or sulfuric acid), leaving you recovered gold to refine.

Copper sulfate is normally blue crystals.
These powders in picture above (look red to me), if it is copper thiosulfate, I do not recognize, as I have never used your method, and have not leached using thiosulfates.

Was this new thiosulfate solution or could it have had Iron in mix?
Could of pins be made of Kovar containing iron?

(Seems I remember a member saying gold from thiosulfate leach was brown to black like gold precipitated from a chloride solution, if so then iron red and brown gold could be mixed in this red mystry powder).

untill you do some testing it is just speculation what you have.

Iron can be tested for. Here is what we have been discussing the gold in and (Iron if that is what red powder is) as thiosulfates.

And Dr. discussing cementing gold from solution using Iron wool makes a lot of sense; this may be a useful tool here.

I do not think we are too far off topic.

 

[Dr. Poe]

I think there is gold mixed into an iron salt. I'm guessing that the iron salt was from the ferrous sulfate that was added.
I think that the ferrous sulfate precipitated something else, but not gold. I repeat: The reason that the steel wool works
isn't that the wool dissolves or cements or displaces but acts as an electroplater. In photography, gold salts used to tint black and white photos don't corrode the silver or replace it, just sticks to the silver. The electromotive difference causes a voltage to flow between different metals. It's this electricity that cleans the gold from the solution. You have a 1.68 volts
push from the gold joining with the metallic iron pull volts of 0.77 totaling 2.45 volts available for reduction. Even though the voltage is less than I like, the enormous surface area of the steel wool some how amplifies the voltage.
Activated carbon does the same thing for cyanide leaches. The carbon doesn't dissolve into the leach, just "adsorbs" the gold onto the surface. Type "adsorption vs absorption" on Google or wiki. They can probably explain it better. Now if the ferrous sulfate did manage to reduce something to metal from the sodium gold thiosulfate, that metal would most certainly react with the gold coming down together. Now also the sodium gold thiosulfate is alkaline, and alkali doesn't corrode iron at normal temperatures. Although sodium thiosulfate doesn't like iron, it doesn't mean that it doesn't like iron sulfide. And I'm sure it likes copper sulfide. Selenium (red) in the ore could cause this enigma as well. That would automatically include copper.
Dr. Poe :mrgreen:

 

[butcher]

Dr. Poe I am going to have to read what you said a couple of times, and I will look up adsorption verses absorption, I can see much information in your statement once I can completely understand it.

I can see where carbon absorbs or adsorbs (soaks up inside or clings to outside attraction) gold without exchanging electrons, or one metal powder may stick to another metal powder (crystallize together without electron transfer), but in my mind electrical potential necessarily would not be a factoring this case.

But as far as I understand in chemistry or electrolytically (plating, cementing, chemical displacement, redox reactions, oxidation or reduction, an electron is exchanged, one metal or chemical looses an electron the other gains an electron,) here the potential voltage is created and would be a factor, or the potential difference of metals in solution.

Two different metals in solution acidic or alkaline, will give a potential difference, one loses an electron the other gains an electron (so one become negative the other positive) as in a battery an electro-chemical reaction takes place (this is theory behind a battery, electroplating and cementing of a metal out of solution onto another metal),

Or when a metal is dissolved in solution (metal ion) and an elemental metal (higher in the electromotive series is place in this solution, an electron is transferred, the metal ion gains an electron plates or cements out (reduced) the elemental metal dissolves to become a metal ion in solution (oxidized) here there is electrical flow of current (electrons moving)

So when you mention a potential difference (voltage), and then it just sticks to with push and pull of voltage (like magnetism) (although magnetism has a lot of properties we use in electricity is a completely different field) this makes my head spin.

Sometimes how you say things confuse me (and almost seem polarized to how I have learned them).

I will go read adsorption verses absorption, and see if that helps.
See ya later
dizzy.


1. Absorption happens when atoms pass through or enter a bulky material like sponges.
2. Adsorption happens when the atoms settle or accumulate on the surface of a material rather than literally entering or diffusing into that same material.




http://en.wikipedia.org/wiki/Adsorption

http://en.wikipedia.org/wiki/Absorption
Ok I have done some reading will read more later, from what I see adsorption or absorption (stuck to outside or sucked up inside), this has nothing to do with electron transfer, so why the discussion of potiental difference?

my head is spinning faster now.

dizzyer
edit spinning head spelling

 

[Dr. Poe]

If you remember that to become an ion the element must become either a proton donor or an electron donor. The gold in solution is a proton donor, the metallic iron is an electron donor. Electricity is not a flow of protons but of electrons. Electron flow needs only a circle (circuit) and a potential difference. Gold is so easily reduced that the slightest voltage provides it with an electron to neutralize the +1 to zero( +1 + -1 = 0) . This would be all there is too it, except it isn't. There's some really complicated math here involved with sodium aurous thiosulfate. I'm getting a headache just trying to remember it. It's a good thing that I'm no longer in college, I might get a lower grade because of this mathematics demon. I think, If I remember even close to being right, that the trisodium sulfur/sulfurtrioxides are holding the gold ion in some kind of circle or box that has to be temporarily broken for the gold +1 ion to be able to react with the reduction elements. Once broken. the gold is released and the circle closes back again. Damn. I'd probably get a D on this paper. Anyway, the stability exceeds the small voltage given by ferrous sulfate, SO2, Stannous chloride, etc. All these reductants give only a single electron whereas metallic iron has three electrons to donate. Still, makes our heads swim (painfully) to fully understand it. I bet there's a metallurgist on the forum who can explain this better than me. :?:
Dr. Poe

 

[butcher]

When an electron moves from one place to another, or one atom to another that is electrical flow.
In our discussion this electron flow is an electro chemical reaction (electron transfer).
We do not have to have an external circuit for electrons to move from one atom to another.
Granted this electron flow will not light a light bulb without an external circuit, but it can put off work as heat in a chemical reaction.

Back to the problem here, did Ferrell use ferrous sulfate to try and precipitate gold from this alkaline thiosululfate leach?

if so could the acidic Iron sulfate precipitant have raised the pH of the thiosulfate leach (if excess used, and would this not effect reactions involved)?

Dr. Poe you mentioned thiosulfate leach (alkaline solution would not like iron
(Do you mean it normally will not put elemental iron into solution)?
And if not what about the iron sulfate salt added would it also stay in solution (normally precipitating the gold) if so why (pH change or what, why would this oxidized iron ion stay in solution).

Poe, You also stated: it doesn't mean that it doesn't like iron sulfide. And I'm sure it likes copper sulfide. (Dr Poe, are you saying these would go into the alkaline leach)?
Normally I think of sulfides as being very insoluble (one reason gold ore is hard to leach is the gold sulfide is hard to break without roasting off the sulfides before hand?


Ferrell, what pretreatments did you do to this ore?
Crushing, roasting, concentration, pre-leaching and other treatments?
This may be your trouble; if ore is not prepared the leach will most likely be unsuccessful.
High sulfide may need roasting with metallic iron in roast to convert the sulfides in ore to metal or rid sulfur and sulfur compounds of ore ,(sulfides are very common), you should find out the chemistry of your ore to determine how to treat it,

Finding out what your ore contains (chemistry wise) may help you to determine pre-treatment, and leach needed, also decide what process would work best,
Do not go by so and so have success with this or that treatment of their ore, what works for one ore will not necessarily work for another, the chemistry involved can be completely different.

Treatment of ore is much more complex than simply picking up some leach and getting out the gold, you may need to chemically change the properties of the ore before a leach will work, or change the leach or conditions or everything. And just because one leach works great on one type of ore it may fail miserably on another type of ore.
I think you may need to go back to the beginning of the process and make sure all of your ducks are in the row.

Gold would not be very valuable if it was easy to get.

 

[Platdigger]

Butcher, you said: "Normally I think of sulfides as being very insoluble (one reason gold ore is hard to leach is the gold sulfide is hard to break without roasting off the sulfides before hand?"

This is one of the things that makes leaching with thiosulfate atractive, no need to roast a sulfide ore.

It seems to me you are trying to take everything you have learned about dissoving gold with acids, to try and make sence of this thiosulfate, which is a bit different, as you can see.

 

[butcher]

Platdigger, your very right, (I am applying the principles I understand probably to the wrong solutions), I am trying to understand this, and also learn the chemistry involved, so are you saying the thiosulfate will break the gold sulfide bond, and dissolve gold into solution (without a roast) and if so does gold remain a sulfide or become a soluble sulfate.

I guess it is hard for me to understandthe principles involved when were on this side of pH scale.

why would not other base metals also dissolve in this lower pH, and keep gold from dissolving or push it back out of solution if base metals are involved.

Platdigger, maybe I am not going to learn this by discussion here, maybe I should do research in another way anyone know of good books on this subject?

 

[Barren Realms 007]

The instructions I have on thiosulphate state that is has a tendency to leach more base metals out of your material at a high PH than it does at a low PH and recomends that the solution be used at a ph of .1-1. Any comments on this?

 

[butcher]

That statment seems to contridict itself pH 1 is acid.
maybe it was read wrong? or just a misprint?

 

[Barren Realms 007]

That statment seems to contridict itself pH 1 is acid.
maybe it was read wrong? or just a misprint?

They recomend it's use on the acid side.

 

[Dr. Poe]

SODIUM GOLD THIOSULFATE (MONO-VALENT), Na3[Au(S2O3)2-2H2O Is the form in "hypo" that we most are familiar. In nature, from hydrothermal vents, geysers, and hot springs it looks like clear to smoky white quartz and is usually associated and encapsulated in quartz. It's very soluble in water, but the dehydrated version less so. Practically invisible, it's usual crystal form is in a "planar" structure. In other words, it makes white flakes. Addition of muriatic acid (HCl) to a leach doesn't change it's basic formulation, but replaces the water of crystallization ( Na3[Au(S2O3)2-2HCl). Non-metallic reduction agents still won't precipitate the gold. This is the main reason most decide to roast the ores prior to leaching. It ranks in the upper 60% of the reasons that refiners lose their gold. Most advise cementation followed by resolution of the solid with AR after decantation and washing of the cemented metals. In the natural, voltage from compressed quartz grows gold crystals slowly. Some cities, like Phoenix, Arizona have spring owners that run the ground water through an activated carbon tower prior to introducing the water to the system just to get the gold. One man told me that he makes up to 4 cents a gallon from the gold within the water. Since he processes thousands of gallons per hour, his money belt is quite heavy. There will be
a lot of happy people to read this post. There will also be a lot of people that wanted this to stay a secret that will hate me for revealing their "Magician's tricks". Please don't tell them where I live. Dr. Poe :lol:

 

[Ferrell]

Butcher, you said: "Normally I think of sulfides as being very insoluble (one reason gold ore is hard to leach is the gold sulfide is hard to break without roasting off the sulfides before hand?"

This is one of the things that makes leaching with thiosulfate attractive, no need to roast a sulfide ore.

It seems to me you are trying to take everything you have learned about dissoving gold with acids, to try and make sence of this thiosulfate, which is a bit different, as you can see.

We didn't do any roasting, either, as we were told by a man who's been successful at using thiosulphate for leaching microscopic gold, that he doesn't pre-roast or pretreat the ore. We didn't do any pretreatment when using the SSN & Butyly diglyme, either, as the lab that tested our ore said it wasn't necessary for that particular treatment. They were able to successfully extract gold from our ore using this method with no pretreatment.

 

[Platdigger]

Butcher, I learned what little I know about leaching gold with thiosulfate, mostly by reading and studying different patents on the subject.