Plattner's Process

[Traveller11]

I was reading through the archives and came across this post by james122964. Hope you don't mind me re-posting it, Jim:


Re: Thiosulfate Questions and Discussion

I would try the HCL/chlorox leach first, but use a sealed container, cut way down on the HCL, and use enough chlorox to convert nearly all of the HCL to chorine gas.
DO not use a glass container, use a 5gl bucket with lid.

I use this for IC chips. I put the ground chips in to about 1/3 of the bucket deep, then I use HCL which the amount depends on the expected metal content, to much does not hurt but is wastefull, I put this in a plastic drink cup (disposable) and force it down into the ground material (so it does not spill) I then add the chlorox which is also in a plastic cup and force down so it will not spill.

I drill a 1/2 inch hole in the lid (relief valve, kinda thing) that I have a rubber stopper to fit. snap the lid on tight. Now here is the tricky part, tip the bucket so the HCL and chlorox mix, then set the bucket back level and test for chlorine gas coming out of the hole with a q-tip that has been dipped in ammonia, white fumes will tell that the bucket is full of chlorine, once this happens cork the hole and roll the bucket around to mix the chlorine gas with the "ore" leave this set for at least 24 hours, rolling again to mix about every six hours or so.

When this is done you can extract the gold by rinsing with water and draining, I reuse the water several times to get a high enough concentration to drop the gold from.
You can then extract your silver chloride with the thiosulfate, I do not bother because of the low value of silver and low content in my IC powder. If your ore has higher then it may be worth it.

The HCL is what reacts with the iron oxides, by eliminating the excess HCL and using chlorine gas, hardly any of the iron compounds are reacted with.

I think if you get the process above down, then you will not really want to use the thio, as you skip many steps involved in the thio process.

This is my adaptation of the Plattners Process that has been used for 100 or so years.

Jim
~~end quote~~
_______________________________________________________________________________________________________________________________________________
I have read further on Plattner's Process and, although there are variations, most of them retain the basics Jim laid out. The most sophisticated variation I read of consisted of a steel pressure vessel into which water and ore were added and then Cl2 gas pumped in under pressure. Once a desired pressure was achieved in the vessel, a valve was turned off on the vessel, sealing the pressurised Cl2 gas in the vessel. It was then placed on rollers and the contents tumbled for several hours, putting the gold in the ore into solution.

I operate a small water system. We inject sodium hypochlorite (NaClO) into our water as a disinfectant. A neighbouring town used Cl2 gas as a disinfectant for years before switching to sodium hypochlorite. When it was in operation with Cl2 gas, the gas was injected under pressure into the drinking water passing by in a pipe, identical to the above variation on Plattner's Process. Interestingly, the sodium hypochlorite and chlorine gas processes achieve almost the same result but there are differences:

Cl2 + H2O = HCl + HClO (hydrochloric acid + hypochlorous acid)

NaClO + H2O = Cl2 + NaOH (sodium hypochlorite + water = chlorine + sodium hydroxide)

Do you see where I'm going with this?

The Cl2 released, when NaClO + H2O are combined, will further react with more H2O to make HCl + HClO. The end product is essentially the same except using NaClO will make the ph of the water higher because of the NaOH formed in the initial reaction.

This is almost too simple. Does Plattner's Process basically use hypochlorous acid to put gold into solution? Is Jim's method working because the combination of NaClO and HCl produces Cl2 gas or is the HCl making the necessary ph adjustment to the ph you would have if only injecting Cl2 gas into the water or is it a combination of both?

I can't believe that chlorinated tap water could potentially dissolve gold.

Jim??

 

[butcher]

Bleach, sodium hypochlorite NaClO solution (sodium hydroxide NaOH is added to the water, this is mixed with HOCL hypoclourous acid to make bleach (sodium hypochlorite), they need the solution to be on the base side of the pH scale, to keep the hypochlorite from changing into chlorine gas and leaving the water).

This bleach raising the pH of your acid, as when the hypochlorite becomes acidic it generates chlorine gas in solution, besides making your acid closer to neutral on the pH scale, there is a lot of water added to your acid which will dilute the solution.

If you can directly bubble the chlorine gas into the concentrated acid you would not have this dilution and the pH will not be affected so drastically.
This way the solution would dissolve and hold more gold in a given amount of solution.

 

[Traveller11]

Bleach, sodium hypochlorite NaClO solution (sodium hydroxide NaOH is added to the water, this is mixed with HOCL hypoclourous acid to make bleach (sodium hypochlorite), they need the solution to be on the base side of the pH scale, to keep the hypochlorite from changing into chlorine gas and leaving the water).

This bleach raising the pH of your acid, as when the hypochlorite becomes acidic it generates chlorine gas in solution, besides making your acid closer to neutral on the pH scale, there is a lot of water added to your acid which will dilute the solution.

If you can directly bubble the chlorine gas into the concentrated acid you would not have this dilution and the pH will not be affected so drastically.
This way the solution would dissolve and hold more gold in a given amount of solution.

Actually, the sodium hypochlorite does not change into chlorine gas and leave the water (bleach solution). Around 10% of it decomposes into oxygen and sodium chloride. The other 90% decomposes into sodium chlorite (NaClO2-) and this progressively degenerates into sodium chlorate (NaClO3-). Sodium hydroxide is added to sodium hypochlorite solutions as a preservative. If the ph of a sodium hypochlorite solution falls below 11.86, decomposition inceases dramatically. Decomposition to NaClO3- can also be accelerated by heating a solution of NaClO.

The whole point of my bringing up what I've discovered about Plattner's Process is that they do not seem to use HCl at all in the process when they are pumping just plain Cl2 gas into the vessel.

 

[Smack]

Plattner's ?

 

[Traveller11]

Plattner's ?

http://www.miningandmetallurgy.com/metallurgy/operation-plattner-gold-chlorination-process

 

[Smack]

Right on lol at me...thought you were referring to Patnor's method.

 

[butcher]

Traveller11,

I stand by my statements above, as far as I understand this the hypochlorite (bleach) will change to chlorine gas if the solution is not basic.

Actually hypochlorite can change into chlorine gas if solution is not basic see equations below, also some study and reading about these reactions.

Unless there is something I am missing this is how I understand it.

Hypochlorous acid (HOCl) is formed from chlorine gas dissolved in water.

CL2 + H2O <-- --> HOCl + HCl

Notice the double arrow in the equation above this means the reaction can go both ways, notice also the solution becomes acidic.

HClO + HCL <-- --> H2O + Cl2
In the reaction above the hypochlorous acid in acid forms water and chlorine gas.
HClO (Hypochlorous) reacts with acid to form chlorine gas in water.

But if we make the solution basic using a base like sodium hydroxide we can make a salt of hypochlorous acid, called hypochlorite (bleach) or in this case sodium hypochlorite.

2HOCl + NaOH --> NaOCl + H2O

Note if the water became acidic this reaction would reverse, and water can act as an acid or a base, to insure the ClO- in bleach does not convert back into hypochlorous and then with acid developed in solution (see reaction above) which could convert back into to chlorine gas (in an acidic solution of water}, the pH of the bleach is kept basic, to keep the chlorine gas in solution as hypochlorite, sodium hydroxide is used thus forming sodium hypochlorite in a basic solution of water.

Dry powders of hypochlorites can be made by bubbling chlorine gas into a solution of sodium hydroxide or other hydroxide's could be used to form other metal chlorite salts.

CL2 (g) + 6NaOH --> 15 deg --> NaClO + NaCl + H2O


Yes sodium hypochlorite can convert to chlorates (NaClO3)and sodium chloride (NaCl) table salt, but not very easily, usually strong heating and concentration of the very dilute solution will only make a small amount of chlorate salts mixed with mostly sodium chloride salts, not much converts to chlorates with a dilute solution, mostly NaCl table salt is formed with a tiny amount of sodium chlorate salt, chlorates are actually hard to make , or to say it another way (it is very hard to oxidize chlorine, chorides, chlorite, or chlorous, to make chlorates).
Electrolysis of a hot concentrated brine solution is much easier and better for making chlorate’s, as it is hard to oxidize the chlorite, or chloride to chlorate.

Heating a dilute solution would not create much chlorate’s mosltly salt NaCl would be the product.

But heating a dry salt of sodium chlorite salt can convert this salt to sodium chloride and sodium chlorate, but still the major product is still NaCl table salt.

3NaClO(s) –heat--> 2NaCl + NaClO3

Again if you wish to make chlorate electrolysis of a hot concentrated brine NaCl would be my choice.

As we seen from the above reaction chlorine gas can be generated from bleach (NaClO) sodium hypochlorite, if the solution is not kept basic, if solution becomes acidic chlorine gas will evolve.

NaClO + HCL --> NaCl + H2O Cl2 (chlorine gas)

The presence of metal oxides Copper, Gold, Nickel,and so on, or even light or heat will accelerate the decomposition of the bleach to form and evolve chlorine gas.

In the reactions we use to refine gold (when using bleach in HCl acid), we dissolve gold into solution by the oxidizing power of chlorine gas in the acidic solution of hydrochloric acid, this gold is oxidized by the chlorine gas, evolving from the HCl acid solution, the oxidized gold in this chloride solution forms a Gold chloride AuCl3, water soluble dissolved salt of gold chloride is formed in this reaction.

2Cl2 + 2H2O --> 4HCl +O2
2HCl + NaClO --> NaCl + H2O + Cl2(g)

Now if I can balance this with gold in the formula, the chlorine oxidizes the gold and the gold forms a salt of gold chloride in the HCl acid and of course there is more going on in solution than the equation shows.

2Au + 6HCl + 3NaClO --> 2AuCl3 + 3NaCl + 3H2O

 

[Traveller11]

http://www.youtube.com/watch?v=wXEQ5rlA8Us

 

[butcher]

Note in the video the bleach was boiled dry to salts, 2 parts of the salt is table salt (soluble in water) and one part sodium chlorate.

3NaClO --> 2NaCl + NaClO3

Also remember household bleach is 92% to 97% water. And only 3% to 8% sodium hypochlorite, and 0.01% to 0.05% sodium hydroxide, so you have to boil away over 90% water from solution to get to the small amount of salts.


In the discussion and posts i made above I was focused on using the bleach as we do to dissolve gold in HCl acid, where we form chlorine gas to dissolve the gold, and also where boiling the solution dry is not our goal, as it would form volumes of salt, with our gold in these salts, and as most of our solution is HCl and the little bleach reacts with the acid and the gold forming chlorine gas in solution leaving less NaClO to form chlorate salts in with the chloride salts.

My focus of this discussion was not on making sodium chlorate, were you are boiling bleach down to dry salt and the solution is kept basic, (no acid in reaction where chlorine gas would escape).

In my opinion boiling bleach down to make sodium chlorate is not very efficient, and would be a waste of good bleach, electrolysis of salt would work much better, although I would not use the video above as a reference to make chlorates for refining metals, the copper from the anodes I would not want in the chlorate salt, Tim Williams is a member here on the forum has a very good web site where he has information on his extensive research into making chlorates and other very interesting information related to what we use in recovery and refining, Tim shows a good method for making chlorate's using electrolysis, and also goes into a good discussions of what works well and what does not and why, so if your interest is making sodium chlorate for refining your metals, check out his web site.

 

[Traveller11]

Note in the video the bleach was boiled dry to salts, 2 parts of the salt is table salt (soluble in water) and one part sodium chlorate.

3NaClO --> 2NaCl + NaClO3

Also remember household bleach is 92% to 97% water. And only 3% to 8% sodium hypochlorite, and 0.01% to 0.05% sodium hydroxide, so you have to boil away over 90% water from solution to get to the small amount of salts.


In the discussion and posts i made above I was focused on using the bleach as we do to dissolve gold in HCl acid, where we form chlorine gas to dissolve the gold, and also where boiling the solution dry is not our goal, as it would form volumes of salt, with our gold in these salts, and as most of our solution is HCl and the little bleach reacts with the acid and the gold forming chlorine gas in solution leaving less NaClO to form chlorate salts in with the chloride salts.

My focus of this discussion was not on making sodium chlorate, were you are boiling bleach down to dry salt and the solution is kept basic, (no acid in reaction where chlorine gas would escape).

In my opinion boiling bleach down to make sodium chlorate is not very efficient, and would be a waste of good bleach, electrolysis of salt would work much better, although I would not use the video above as a reference to make chlorates for refining metals, the copper from the anodes I would not want in the chlorate salt, Tim Williams is a member here on the forum has a very good web site where he has information on his extensive research into making chlorates and other very interesting information related to what we use in recovery and refining, Tim shows a good method for making chlorate's using electrolysis, and also goes into a good discussions of what works well and what does not and why, so if your interest is making sodium chlorate for refining your metals, check out his web site.

The point of showing the video is that the decomposition of sodium hypochlorite, in a base environment, does make a goodly proportion of itself into sodium chlorate; although you are correct in saying more sodium chloride is produced than sodium chlorate. This will occur at room temperature, as well. It is a challenge in the water treatment world to obtain freshly manufactured NaClO and to store it at temperatures low enough to retard the decomposition and to use it up in a timely fashion. I am not sure of the health effects of sodium chlorate and sodium chlorite in drinking water but I know Health Canada limits each to 1.0 ppm in drinking water.

The decomposition to NaCl has an additional problem; the higher the salinity of the NaClO solution, the more rapidly it decomposes. For this reason, the tanks we store NaClO in must not be topped up but cleaned between fillings.

I have not experienced Cl2 gas being given off by the NaClO in our tanks but, then again, we do not let the ph fall below the manufactured level of just over 12.

What really fascinates me about Plattner's process is two things.
1. The original process appears to use nothing but straight Cl2 gas pumped into a vessel under pressure. This, according to water treatment chemistry, should produce HCl and HClO and should make the solution mildly acidic, directly coinciding with James' recommendation to cut way back on the HCl when mixing it with NaClO.
2. James' claim that, by cutting back on the HCl, the leach tends to avoid iron oxides. This reminds me of the info I've found on the iodine/iodide leach process. It seems that iodine/iodide has a ph of between 4-5 and, at that ph, is selective for gold. However, so I've read, if the ph falls below 3, the iodine/iodide leach will begin dissolving iron and other base metals.
Could the same be true for chlorine? Is this what James has discovered in his HCl/NaClO leach by cutting back on the addition of HCl?

 

[Traveller11]

I'm not sure if I made that as clear as I wanted to.

I was trying to say that, if the I2/NaI process is ph dependent on whether or not it is selective for gold or, with ph under 3, it will dissolve base metals as well, is it possible that the HCl/NaClO process is also ph dependent? Did James, by adding far less HCl than normally used, make the ph of the leach solution higher and, inadvertently, make it selective for gold, ignoring the iron oxides, as he claimed?

This is why I keep going back to Plattner's process, which uses no HCl at all. It achieves a lower ph by allowing CL2 gas to be absorbed by the water under pressure, making HCl and HClO (hydrochloroc and hypochlorous acid).

 

[butcher]

I really do not know the answer to this question.

Here is my opinion only.

Chlorine will attack base metals; my guess is more readily than it would attack gold.

Chlorine gas will attack these metals without acid, although the acid can assist in the dissolution of these metals, chlorine gas is missing electrons and will take electrons from metal atoms outer shell, the base metals will give up these electrons very easily, some metals more easily than others (see reactivity series of metals), including iron metal, the more reactive the metal the easier it would be for chlorine gas to attack or take electrons from the metal and form metal chlorides.

Iron metal can be attacked by chlorine gas, forming iron chlorides.
Just as gold can be attacked by chlorine gas, forming gold chlorides.
The chlorine in the reaction is reduced (gain of electrons), the metals are oxidized (loss of electrons).

Iron hydroxides, or oxides are not elemental iron metal, and these iron hydroxides can be harder for acids to attack, iron hydroxide is even hard for aqua regia to attack where gold will dissolve easily.
(Similar to how iron sulfides in ore will not easily break down and give up there hold onto gold in a leach, without roasting the ore to remove the sulfide from the iron).

I have a jar red powder of iron hydroxide, that acids were used to dissolve gold even after the gold was put into solution these red rouge powders would not go into solution, in fact it would also be very hard to reduce these red iron hydroxide powders back to elemental iron, much harder than most all of the other base metals or hydroxides of other base metals, I just feel iron is somewhat of a strange animal when it comes to chemistry, as compared to most of the other base metals.

I think James main goal was to generate chlorine gas, and in the sealed bucket with a cork vent relief, he did not need much acid, just enough to make the sodium hypochlorite slightly acidic so that it would generate chlorine as a gas, as far as his statement the more HCl would attack the iron hydroxides, this really does not make sense to me at this point as HCl will not dissolve iron hydroxide, but chlorine can help to oxidize it to where some can go into solution as FeCl3, so unless I do not understand something here I do not think it would have mattered if he had used more acid in his bucket, I do not see where more iron hydroxide would have dissolved either way.

I do not think chlorine gas is pH dependent on its attack of metals, as in its reduced state (chlorine gas) it is a strong oxidizer with the atoms missing electrons and thus is a strong oxidizer for metals.

In my mind I guess it just boils down to how strong of an oxidizer the gas, acid, or even neutral water, or base solution is, and how easily reduced the metal atoms are, that are introduced into these solutions or gases, as to if or how easily the metals will give up its electron and be dissolved into the solution or form salts of metals in the reaction.


One of the main reason I see many of the halogen leaches like iodine or chlorine as being pH dependent, is to keep the oxidizer in solution and in its elemental state to where it can come into contact with the metals and oxidize the metal, if the halogen was reduced it would not attack the metal, and if it left the solution it would not come into contact with the metal.

 

[Traveller11]

This is very puzzling. I understand what you are saying about Cl2 gas attacking metals and not needing to ph dependent to do so but, I wonder if there is not a little more to Plattner's process than meets the eye.

Two variations on Plattner's process I read both involved introducing Cl2 gas into a vessel, partially filled with ground ore and water, under pressure and retaining that pressure by means of a valve or stopper. I am not sure how this would compare to James' method of producing Cl2 gas by mixing NaClO and HCl in a sealed chamber, except to speculate that the production of Cl2 gas in a sealed chamber might raise the pressure inside that chamber by an atmosphere.

This is where go back to my experience with water treatment. Cl2 gas introduced under pressure into water will dissolve (is that the right term for it?), just as CO2 or N2 will dissolve at 25 psi in water. Once dissolved, Cl2 gas, as you pointed out, becomes HCl and HClO. Could it be the HClO that is the oxidizer at work here?

I wish James would read this and share a bit more of his experiences with us.

Are iron oxides and iron hydroxides similar?

 

[butcher]

There are several oxides of iron, some of the more common we see as rust.
Or in the ore as hematite (Fe2O3) ,
And magnetite Fe3O4 or (FeO-Fe2O3), (named because it can be a magnet).
Iron oxide FeO wustite.
Fe(OH)2 ferrous hydroxide.
Fe(H2O)6 or Fe(OH)6 is also possible.
I think iron oxides and hydroxides react very differently, the only similar thing I can think of is they all either have or came from iron, they really react differently from each other in solution or in electrolysis.

I would like also to learn more about the iron compounds it is a very interesting study and can be very useful if working with ore.

I think chlorine gases attack on gold is accelerated by heat and temperature, pressure can also raise a temperature of a gas, or change the boiling points, and the Plattner's process is using this to its advantage, as well as being able to keep the chlorine gas in contact with the metal long enough for the reaction to take place.

I really have not studied or used the Plattner’s process so I cannot really comment on it much,