Potassium Iodide-Iodine gold etchant

[Juan Manuel Arcos Frank]

Harold_V:

Thank you very much!!!!...I do appreciate all what you have done for me.Now I know how to quote.

Have a nice day.

Manuel

 

[Juan Manuel Arcos Frank]

Pohyh:

This is what de Forum is for.Here is the cherry pie.

Regards.

Manuel

 

[pohyh]

Dearl All

While woking for my project, I realised that the tap water I used for AP project seem to be "etching" my gold away. Futher investigation reveal that the residual Cl2 in the water might be responsible for this process.

I do not want to spend money on DI water and thus I used condensed water from my airconditional unit and now the problem have been solved. A checked with the resistivity meter indicate that the resistance of commercially availble DI water and the condense water is the same.

So save money by using recycle condense water for your gold recovery.

Cheer! :wink:

Poh

 

[DNIndustry]

Sorry Ive been away... Been prototypin.

I guess a back story, Ill also have to dig up my notes later so if I miss something just ask.

I attached the 2 patents that have been mentioned. The first is the KI & Iodine. The second is NH4I/I2

Comparatively using potassium iodide is much more costly than ammonium Iodide. The Problem is that the KI concentrations shift up and down. Always having a fresh batch mixed is much more desirable. The other draw back of KI is the acidic nature. PH is 2-3 ish if recall. Because of this the etching rates are much less controllable. If it is left in too long it will chew right into the nickel substrate and the copper below. ( If on pins)
The PH of NH4I is 7.5-8.5. slightly basic and much more selective.
I would generally do the etching at 40-50C ish. It can be done in a container in a waterbath, crockpot to cheepsk8s
Fume wise a hood is not needed, if you do it properly. A mask is recommended for some portions (initial mixing, precipitating the Iodine back out.)
The nice part about experimenting with KI thought is the amount of elemental Iodine you can accumulate. -

A 500g Container of KI yields about 3 mols of KI-
K=39
I=127
KI=166
Of the overall mass there is 382.5g elemental Iodine/500g KI

I may have said this previously but I am easily pushing 6lbs of Iodine. It is cumulative, any reuses. The potassium is lost to the gold gods.

So you can atleast see the cost difference,
it takes about 450g I2 & 97mL's NH4OH & 47 mLs 30%H2O2 (make sure I dont have these numbers switched)
Comparatively the ammonia is much cheaper, and controllable

* Before I get flamed, A public service anouncement, make sure you add the H202 exacty like and when it says* That one little oxygen molecule is what prevents making the bad stuff.


In this case more is not better,
H202-Make certain that you are using 30% not 35%. If so properly dilute your solution. Stir excessily well. If you follow the patent
Add 500mLs Water to a 2 liter reactor
Add 350g I2 crystals & stir
-----
The iodine is not soluble in water. Infact one time I spilled half a pound on the floor. Scraped it up, rinsed it, tossed it back in. Not even a slight stain.
-----
Add the H202
-----
This makes the Iodine soluble
-----
Add the NH4OH- Use a mask it is harsh, add slowly in increments and keep the stirring up.
-----
I took a 5 gallon bucket, cut a hole in the lid. Put a bearing in the middle and mounted a paint vortexer, put my drill on the other end and bam, best $3 I ever spent.
H202 oxidizes the Iodine, If you read further it talks about adding 3% h2o2 to the bottom of the mixture during stripping, and 30% during regeneration.
Im jumping ahead but the mixture is actually a 2 level suspension; not really visibly noticable. The NH4I etchs the gold/pt/pd/Ag etc, Then Iodine binds with it. Small amounts of h202 will free up more iodine thefore speeding it up.
* A note of caution if you do this, do not add it near the pieces being etched. It will seriously speed up; Ive stripped parts and only puting the 3% kicker by one of the pieces. All the parts came out looking like brand new nickel plate...minus the one with the hole in it down to through the copper
*Agitaion is a huge help, remember it becomes a suspension.
Now that I think about it, when I used KI the results even in batch varied (amount etched) The NH4I everything is uniform and bright n shiny. I know Ive posted pictures before.. pH is important, less acidic, less basemetal etching.
Which reminds me...Ive been building this rube goldberg reactor/ion exchange column, after alpha testing my AP, HCL-CL, Resin load/elute process. I am going to try AP, KI/I, Resiload elute on my foils. The best of both worlds. Copper is gone, KI/I will eat it in under 3 mins, then load it onto the XAD-7, elute with acetone+hcl.
Heck, I wonder how well HI+H202 would work for base metals
Digest it with HI/I
Load....
Talk about fast an pure, HCL-CL & XAD7 without disolving basemetals yields 99.96% with alluvial ore, imaging feeding it clean gold...

I will continue this later, post questions, comments, Ill answer.
In the mean time
*Do not try the "make it more basic precipitation theory for gold"
*Do not use hydroxylamine hcl unitl I can get into the use of DiBasic Ammonium Phosphate buffers.
*Do add more H202 when mixing if it still smells like ammonia after a few minutes of beating it with a pail mixer

-DNI

 

[pohyh]

Hi All

This is the first time trying to post a picture in this Forum. Thank Steve for his tutorial and let see what do we have in Singapore. This are typical precious metal containg sample we get from semiconductor industries.

I am posting 4 pic today and I just post one by one. To play safe!

Regards
Poh

[img:648:486]http://img519.imageshack.us/img519/2384/miscgoldplatedpins.png[/img]

 

[pohyh]

Dear All

Another pic.

BTW Anybody have any working experience on this HP Injet printer head contact?

Regards
Poh

[img:648:486]http://img259.imageshack.us/img259/6942/hpinjetprinterheadconta.png[/img]

 

[pohyh]

Dear All

3rd picture.

[img:648:486]http://img259.imageshack.us/img259/8995/probercontactpins.png[/img]

 

[pohyh]

Dear All

Last picture for today!

Have a nice day!

Regards
Poh

[img:648:486]http://img17.imageshack.us/img17/21/semiconductorplasmaring.png[/img]

 

[usernameguy]

Hey Randy, et al.

Thanks for asking. I'm new to all this stuff on the refining end, so still learning terms and such. sorry for the delayed response, family is ill right now. To answer you question, I work in a semiconductor processing facility, so I'm sure I can be of some use if you all are having issues at times.
my process is relatively simple. The I etchant is used by the facility to etch thin films of Au to create layers of patterns from the wafer (Si) up. The Au that's either plasma sputtered or evaporated then gets covered with a photodefinable polymer and developed away where it's been exposed is 4 9's pure. 99.9999!!!! The Au that's now exposed where the polymer was dveloped away gets etched in this I solution. It's purchased from a chemical supply company, and thrown away as waste WELL before it's saturated. I'm just curious if what I'm dropping out with pure crystaline KOH is pure Au or not. It's doubtful there's much Pt, but possible. The thing is I'm getting a grey precipitate and there's no way to know how much I should be getting. I'm also secondarily curious if the etch rate for the people processing is linear or not, because if it is, I could convince them to not dispose of the soltion so quickly, and this would mean less waste, and less material for me to deal with also. lemme know what anyone thinks, or if you have any questions.
Thank you in advance!
The other waste solution I have access to is a Au plating solution BDT 510 I believe that again is commercially available. It was recommended to precip this using H2SO4, and I'll be trying that this weekend.
-Guy

 

[goldsilverpro]

99.9999 is SIX nines. Count them.

Please let us know how the 10% H2SO4 works on the BDT 510. I would try a small sample at first.


Pohyh,
Too bad you can't use cyanide. Everything in the photos would fit it perfectly.

 

[pohyh]

Hi GSP

I know very well cynide is the most effective interm in etching as well as cost....BUT, we are in Singapore. Although we can buy cynide (we have licence to do so) but to do it is really pain in the neck!

Firstly Environment officer will inspect the storage facility. They will ask tons of questions on the intention. They will check on daily usage. They will do a surprise check on your stock and so on and on!

With those kind of harrasment, I think I would rather forget on using them. Afterall, the disposable issue is very costly for cynide in Singapore.

After giving you all the excuse, I must admit, the most important fobia I have is that one of my supervisor commit suicide with cynide (way back in early 80) and I am always shy away from it. Afteall, I am such a clumsy guy that I am not surprise if pour acid into the cynide solution one of this day.


Anyway, any suggestion on the HP Injet printer head contact. KI3 seem ineffective as the gold is sandwitch inbetween 2 layer of polymer.

Regards
Poh

 

[goldsilverpro]

Incineration?

 

[usernameguy]

Our metals guy always refers to the # of 9's as how many are behid the decimal since the 2 in front of the decimal is inferred. Maybe that's just his own personal way of doing it.
Anyway, Pohyh, Parylene is a very common polymer used to protect electronics, however I think it's mainly used for biomedical devices since it's one of the more biocompatable materials that can be evaporated uniformly, so this may be worth a try. I can ask what's used to remove this, but I'm sure it's not easy. Alot of the polymers that are solvent resistant after curing are an endless pain in the arse to tool engineers like myself because they're so hard to remove. sometimes, they end up rendering $100K tools useless because hot HF isn't an option in the areas these materials accumulate on the equipment. I'd google parylene and see what's mentioned for removal. Even if your material isn't exactly parylene, I suspect whatever can remove it can remove that. As the pro said though, burning it would be simple, cheap and effective. I don't imagine you need to protect any of the other materials involved.
-Guy

 

[goldsilverpro]

Our metals guy always refers to the # of 9's as how many are behid the decimal since the 2 in front of the decimal is inferred. Maybe that's just his own personal way of doing it.

Your metals guy is wrong. Colloidal silver people make the same mistake when they talk about pure silver wire. They're wrong, also.

I guess that one can count the 9s anyway they want to. However, universally, in the PM trade, all the 9s are counted, including the two on the left of the decimal point. Counting the 9s in a different way will just create confusion.

At one time, I was considering selling 4-9s (99.99%) wire to people that made their own colloidal silver. There was about an 800% profit in it. Some sellers were selling 3-9s and 4-9s wire and were saying it was 99.999% and 99.9999% pure, respectively. Anyone that has a grasp of metal purities would know that that was BS. I don't think these sellers were making these ridiculous claims fraudulently. I think they were making them out of shear ignorance. To me, though, it certainly confused the issue.

 

[pohyh]

Hi GSP

I thought of incineration as well. But when I incinerate them at 800 C, I cannot get any gold. Perhelp the gold layer is thin or Au evaporate in that temperature.

Any comment?

Regards
Poh

 

[Harold_V]

I thought of incineration as well. But when I incinerate them at 800 C, I cannot get any gold. Perhelp the gold layer is thin or Au evaporate in that temperature.

I'm jumping in this thing without knowing the facts, so please bear with me if I am screwed up. Please set me straight if so.

If you have something that is gold plated and it seems to lose the gold in incineration, rest assured, it has not been evaporated. Gold has the ability to migrate into other metals, although not all. It is for that reason they plate nickel on copper based alloys before applying gold. I expect that if you incinerate, and can't see the gold, it is still very much present, just disseminated in the substrate. Dissolving the base material is likely to yield the seemingly lost gold.

Harold

 

[goldsilverpro]

At that temperature, there would be no evaporation of the gold. I would imagine that, while burning off the plastic, there could be enough turbulence to send the light ash containing the gold into the air. I still think that some sort of controlled incineration would collect the gold. Don't ask me how. It's something one must play with. It's a difficult item. Do you have any feel for the amount of gold in that material?

 

[DNIndustry]

Can some one quick throw up the balanced equation for Au NaClO HCL
Im reading through some documentation, and I know this guy is smoking crack....

Just out of curiosity how does nickel respond to HCL+CL.

 

[pohyh]

Hi GSP

You might be right. I will try to extract the base metal attached to the crucible and let see wheather I can find any of my lost gold. Incidently some one told me that if I use a zicromium crubile with lid, I mght solve the problem. BTW anybody have that experience?

FYI, Harold_V, the gold content is approx 1 to 2%.

Regards
Poh

 

[lazersteve]

Can some one quick throw up the balanced equation for Au NaClO HCL

This primary reaction can be considered the reaction of Cl2 with HCl:

2Au + 3Cl2 + 2HCl --> 2HAuCl4

The Chlorine is generated in situ via the reaction of the sodium hypochlorite with the HCl.

Just out of curiosity how does nickel respond to HCL+CL.

It dissolves.

Steve