Potassium Iodide-Iodine gold etchant

[Juan Manuel Arcos Frank]

Pohyh:

I am working with PM recovery from printing scrap(i.e. fil circuits of ink cartridges like you have posted) and I can not be able to get a measurable quantity of gold from 200 film circuits,of course,my scale just can weight 0.1 gr.

The little circles in the film circuit are gold plated,there are very thin wires inside the film circuit ,I do not know if they are gold or copper,since I got a poor quantity of gold I sent them away,I despair with ease.

I hope post my research results soon.

Regards

Manuel

 

[pohyh]

Hi Manuel

Thanks for your input.

The top layer can be remove by the addition of tetrachloroethane (TCE). After socking the layer with TCE, the polymer basically peer off and float to the top. The small round gold plated disc as well as fine wire drop to the bottom. I strongly believe all those are gold plated.

After saying that, I must say that NOT all the printer head contact is gold plated. I have collected quite a few different type, for other brand of printer are not gold plated. The colour of the disc is slightly brownish.

TCE is good solvent but it does not smell too nice. Just for your information. That is why I am looking for other better technique.

Regards
Poh

 

[Juan Manuel Arcos Frank]

Hi Poh:

Thanks for your information.Have you tested the small wires for gold?.They seem to be copper.

Regards.

Manuel

 

[usernameguy]

In the semiconductor industry (at least our research facility) the most common metal deposited before Au is Ti. This is used as an adhesion layer since A doesn't adhere well to Si, SiO2 and a lot of various other materials. the adhesion layer is typically Very Thin respectively. On the order of 50 Angstroms (5nm) (the distance you fingernail grows in 5 seconds). The Au is then however thick the process requires (typically less than or right around a micron. These films are still so thin, they float around in solvent before settling, like gold leaf.

I have a kind of unrelated question. I'm going to precip my Au plating solution today as suggested by GSP, but the last time I filtered off my Au powder precip'd from the I etch solution, I tried to burn off the paper filter using a normal butane torch like that used to solder pipes. It smoked something fierce, and had a very dark smoke. I surmised I was starting to burn off the Au. Any ideas, and is my assumption even possible?

Thx,
Guy

 

[AuMINIMayhem]

TCE.. that should come with a very large warning sign.. :wink: it's brutal stuff.

I too looked into print heads at one point... there's one of those "Cartridge World" type places near me that junks all the old printer cartridges they have no use for.. the print heads (especialy HP model inkjets) do "look" like they have quite a bit of gold, but indeed angstroms is the key word.. they are nowhere near HGP (heavy gold plate) it's just enough to keep them from corroding from the ink.. which is another problem altogether.. I really thought better of dealing with print cartridges the first time I tinkered around with one.. injket ink not only stains it STAINS! The ink is formulated on such a small scale (nm) that the particles will damn near tatoo you just by contact.. the particles are indeed small enough to absorb instantly and become a sub-dermal stain that takes quite some time to get rid of (Ie: you'll have to wait to shed those cells).. not to mention clothes, etc.. wasn't worth harvesting, IMHO, but I'd be interested in yield data for sure :wink:

 

[goldsilverpro]

You won't evaporate metallic gold. It can be mechanically carried off in the smoke, especially with a lot of turbulence. You must have a lot of other stuff combined with the gold. However, if you don't like the smoke, can't you leach the gold from the precipitate with AR or, maybe, one of Steve's methods? You're going to need to purify it eventually, anyway.

 

[pohyh]

HI GSP

I have tried the AP method as suggested by Steve. Initially, some of the gold plated disc came out but disappear (probably the cu portion being dissolved), but most of them stick to the plastic. All of the fine wired remained there.

As mentioned previously, the metal are being sandwiched in between 2 layer of plastic. As long as I can get to etch one of them, I should get the problem solved. One of the study is obviously suing the chlorinated solvent eg Tetrahydrofuran (THF) or Trichloroethylene (Chloroform) or Tetrachloroethane (TCE). All these 3 solvents work but they stink and all of them are not environment friendly. As mentioned by AuMINIMayhem, TCE is BRUTAL!

Anyway AuMINIMayhem, Hewlett Packard has a IJMS (Injet Manufacturing) facility in SIngapore. Thanks goodness, all the contact we get are production scrap and not from individual injet printer head. You are right, it is pain to work with used injet. The ink simply stain!

On the other subject, usernameguy suggested the sandwich layer might be parylene. Obviously knowing that HP Singapore do not use parylene in their process simply eliminate parylene as the sandwich polymer.

Hi Manuel, previously we have do an etch method via dilute nitric acid and followed by AR and confirmed that it is gold and by wt/wt basis, it range from 1 to 2 %. There are such a big variation depending on which portion you test. Gold plated dics portion higher compare with fine wire portion.

Thanks all for yours input and all your suggestion made this discussion lively. Keep it up.

Regards
Poh

 

[usernameguy]

Can Au be evaporated in vacuum? The process they use in my lab they "call" evaporation, but... The vacuum has to be very low (or high depending on how you look at it. technically high)in this case Ultra high vacuum. The gold which is extremely pure, as stated 4 9's or better is heated with an electron beam (electricity) focused and directed with magnetic fields. The material Au, Pt, Al, whatever then coats everywhere in the chamber, but mostly up which is where the substrates are mounted on a spinning carousel a specific distance from the source in order to achieve a uniform continuous film. I'm just curious if you guys think this is truley evaporation. I know this is a far cry from a butane torch at atmosphere, but...
I'll start another thread if this is of interest. I don't want to hijack this one. I too am learning much and using a similar process. I think the Au I precipitate from the Iodine solution using KOH is pure though from the patent I got the process from.
by the way, that's actually true about the fingernails. pretty cool huh? We image things on this scale(beyond the physical limits of optical microscopy... visible light's wavelength is way too big). If the temperature of the sample is different than that of the chamber, you end up chasing the thing around you want to see. sorry, I'm kind of a lab geek and new to forums. I've noticed people usually keep ther comments short.
-Guy

 

[pohyh]

Hi Guy

The term "evaporate" I used is refer to a suggestion that gold "disappear" in the surrounding environment during heating and not the physical evaoporation of pur gold as we have studied in our science lesson. Looking at the physical properties of gold inself, the melting temp is already high, the evaporation is difficult to attain in the normal environment.

Anyway, the picture I post simply mean to tell the member of Forum what I have been working with. I really appreciate the input from the member on the way to remove the gold from the injet printer contact head.

Anyway, I started this tread is on the halide etching. I am here to follow up a bit what I have learn from the process.

For the KI3 etching, to recover KI in the spend etching solution is out of the question as KI gone to the gold's god, as one of the member put it. Nevertheless, to reconever Iodine from it is a simple task (by adding H2O2). To made the process economical (as KI is expensive, approx US$70/kg), I though if I2 can change to KI in the folllowing equation:

I2 + 2KOH (aq) --2KI + H2O + H+

It is a wild idea right from my crazy mind. Just to see any suggestion from the Forum member.

Any comment?

By the way, DNI has suggested using Ammonia solution in replace of KI. It definately solve the economical issue (Ammonia solution 21% only cost US$0.8/kg) and it work pretty neat. Off course, you must work in the fume hook or well ventilated enviroment or your neighbour will come after you...real fast! :lol:

Regards
Poh

 

[Juan Manuel Arcos Frank]

Poh:

Be careful with the wild ideas from your crazy mind.....they can become reality!!!!!!!.

You can make KI like you said,you just need an old trick,here it is:

You have to add some organic acid to the mixure and probably heat a little.If you add iodine to potassium hydroxide this will happen:

3I2+6KOH=5KI+KIO3+3H2O

you will make potassium iodide,but you will get undesairable potassium iodate too...so the trick is adding some formic acid wich will react with the potassium iodate and will form pure potassium iodide,a lovely process,does not it?

KIO3+3HCOOH=KI+3H2O+3CO2

Do you want to know more about this process,let it be:

Mix 1270 gr of iodine(5 mol) with 560 gr (10 mol)(dissolved in 2.5lt) and heat a little bit to complete the dissolution,the iodide and iodate mixure is formed,then heat and slowly add 230 gr (5 mol) of(100%) formic acid ,you will see some fumes and a decolorization will ocurr and you will get a pure solution of KI.

Poh,I welcome you like to experiment...I know you have some H2O2 (30%) in your lab...Would you do for me an experiment?

Regards.

Manuel

 

[pohyh]

Hi Manuel

My gut feeling tell me my crazy idea might be reality as the synthesis of KI is via formate path (ie addition of formic acid) but I am simply refuse to accept it. Obviously, I want to try and if what you say is achiveable, then we can come out with an economical way to etch gold.

As the Singapore Rule on H2O2 is concerned, we can buy H2O2 as long as it is less than 20% concentration. SO I have plenty of 19% H2O2. I am more than willing to try the H2O2 experiement for you if I can do it with that concentration. PM me if you want that discussion to be private.

Again thanks for your input!

Regards
Poh

 

[pohyh]

Hi All

Just an update on my recent finding on recovery of precious metal from the sandwich layer of Hewlett Packard Injet printer head contact.

Basically this sandwich layer must be removed before the gold plated metal can be removed. After a series of experiement, I found the the following procedure work pretty cool.

1. Soak the above printer head contact with 50% H2SO4
2. add 1 part of H2O2 (~20%) to 5 part of diluted H2SO4
3. Shake it gently
4. A few minute later, you basically see the sadwich polymer "charred" and float to the top
5. If necessary, add more H2O2 until all the sandwich layer is being removed.
6. Now you are ready for the next step to remove the gold plated metal.
7. The choice is yours! You can do it with Steve's AP or AR method or dilute H2NO3 method.

Good luck!

Regards
Poh

 

[Juan Manuel Arcos Frank]

Poh:

Nice work!!!!!!....Can you tell us about gold content in those films cartridges?

Have a nice day.

Manuel

 

[pohyh]

Hi Manuel

Oh ya, you shold be able to get around 10 to 12 gram of gold for each kilogram of injet printer head contact. That would equate to 1.0 to 1.2 % of gold.

The variation depend on the model of HP injet printer.

Again good luck!

Regards
Poh

 

[Juan Manuel Arcos Frank]

Poh:

Thanks a lot...I do appreciate all the information that you have provided to this Forum.

Have a nice day.

Manuel

 

[Juan Manuel Arcos Frank]

Poh:

Look,I have some information to you but I can send it to you in a PM message because it is 30 Mb..May I have your e mail?...My e mail is [email protected]

Regards

Manuel

 

[pohyh]

Hi All

I am back!

Just to update some of the things I have learn from this Forum. I have lay my hand on some base metal etching technique suggested by the very experience panel member namely acid peroxide (AP), poor man aqualigia (AR) as well very cools way to made gold chloride by chlorox methods.

In addition, I have also tried Nitric Acid + H2O2 (NP) as well as Nitric Acid + Sulfamic acid + Urea (NSU) as suggested by Manuel.

All the methods of base method etching work pretty well. The choice obviously depends on individual preference. Unfortunately, some form of acid fume has been generated especially when the nitric acid is been used. It simply stink!

I want to extract gold but I want to do it in a more environment friendly manner! After going through the above process, I am more determine to come out with halide etching method and I have decided to set myself a target to come out with a cook book with Potassium iodide Iodine etchant method soon!

Anyway, I have an interesting question to post for the member.

While extracting gold finger with Nitric acid with H2O2 (NP), after all the base metal have been dissolved, the blue colour liquid have decant and the gold flake have been collected using filtration method. Some of the very fine particles cannot be remove through filtration and they form a light brown mud at the bottom.

Upon adding NaoH, this mud generated ammonia gas and the process is exothermic. The mud turns to tick dark colour. May I know what this mud is?

Attached 2 picture before adding and after adding NaoH for your information.

Regards
Poh


Before adding NaOH

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After adding NaOH

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[qst42know]

Did you test these solutions for PM's with stannous chloride (SnCl) before you added the lye?

 

[pohyh]

Hi gst42know

Thankd for your suggestion.

The top part of the solution before lye is added should be copper, I assume since it is blue in colour. The mud probably consists of very finely devided gold which sip through the filter paper. Since it is solid particle (or more toward colloidal instead) in nature, will SnCl work?

I add NaOH to it so that I can neutralsed yje solution before I etch it again with HCL.

Anyway, I will tried it next time.

Regards
Poh

 

[qst42know]

I wouldn't harm anything to test while the solution was still acidic. To detect other metals of interest, palladium, or silver. It could also make certain nothing had contaminated your solution and dissolved some gold.