# Some doubts on gold recovery



## Wingedcloud (Nov 20, 2014)

Hello everynone. I am new to this forum, but for the little time I've been here, I know I've come to the right place to get some support in my "quest" to recover some precious metals from PCB's, which leaves me happy, because I was feeling a little unsupported trying to do something right.

If I may, I'm gonna start by telling a little bit about my background.
I recently finished my Master's Degree in Environmental Engineering and i did my master's thesis in recovering precious metals from PCB's by hydrometallurgical methods.
During my work, i tested dissolving the metals in aqua regia and precipitating the gold by means of ferrous sulphate and sodium nitrite. During my research, I've come across Hoke's book, and knew about some of the existing processes there are to recover gold from solution. However, having an academic background, I'm used to having some concrete values and experimental conditions, some characteristics this book lacks in some extent. Im not saying that that information not only but also emphyrical, result of much years of working in this "business", are inferior to some information I found in some scientific papers and articles during my thesis research, and I am more than ready to follow those instructions if that means I'm going to suceed.

After I finished my thesis, I kept reading, studying and searching for more information about hydrometallurgy and even got some powder out of some CPU's I expect to be gold. Just waiting to have material to melt it and find out 
I have a lot of material waiting to be processed, like some more CPU's, memory sticks, motherboards, cellphone boards, etc.

But enough of my story...on to my questions:

Regarding an initial HNO3 base metals removal:
- Which mass/volume ratio should I use?
- At which temperature should this process be done and for how long?

Regarding AR precious metals removal:
- Should I follow Hoke's 1:3/1:4 HNO3/HCl ratio or do the "small HNO3 aditions" process? When do I know I've added enough HNO3?
- At which temperature should this process be done and for how long? (during my thesis I used 90ºC for 3 hours)

Regarding gold recovery from solution:
- SMB vs Ferrous Sulphate vs Sulfur Dioxide ? 
I've found this video about sulfur dioxide gold recovery and I would like to know your opinion about using it on PCB's aqua regia gold removal, considering the gold content is much lower than the one on the video.

https://www.youtube.com/watch?v=1Usv2Lh10nQ

- Should I heat my solution to do this process?

I would like to say thanks in advance to someone who can help me with my questions and apologize if there are answers somewhere in this forum and I've not been able to find them. Feel free to ask anything that can help you help me 

Best regards to you all


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## nickvc (Nov 20, 2014)

Welcome to the forum.
I would first point out that using AR on circuit boards is a waste of chemicals in every sense.
Forget what theory taught you and learn how the real world works, spend time and energy reading and learning here, it's the best free education you will ever receive.
Please don't take this wrong but you have a lot to learn about how to make the whole process profitable not just possible, your previous research should make the understanding easier but never think your above those who do this or did this for a living. Some of the guys here would struggle to string a decent sentence together but what the heck they are damn fine refiners who will make a monkey out of those who think they know better.
Phd, doctorate etc count for nothing here, we are men and women of science who will only listen to those who can walk the walk not just talk it.
There are thousnds of posts and threads covering most examples of recovery and refining, each picked over and dissected by experts with hundreds if not thousands between them of years of actual hands on refining experience.
Start at the beginning and learn the real methods and processes that work, if you feel after that you have a point to add or a process please feel free to add it to this forum, but be aware it wil be dissected and discussed at length by the members.
Good luck.


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## Wingedcloud (Nov 20, 2014)

Thanks for your answer.
By telling my background I didnt have any intention to put myself above anyone. I know I have a lot to learn and I am willing to do so by learning from people on this forum, who have been doing this for years and got their knowledge from hard work. 
I seriously respect that and I had no intention to disrespect anyone with what I said.


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## eastky (Nov 20, 2014)

nickvc excellent post.


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## FrugalRefiner (Nov 20, 2014)

Wingedcloud,

Welcome to the forum. I don't know where you got your copy of Hoke's book. There are a couple of different versions available on the internet as well as here on the forum. I would encourage you to download one of the versions in my signature line. It includes a lot of corrections to the original scanned version on this forum as well as an introduction that discusses some of the safety issues that weren't well known when the book was written. You'll find answers to at least one or two of your questions there.

Dave


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## Wingedcloud (Nov 20, 2014)

FrugalRefiner said:


> Wingedcloud,
> 
> Welcome to the forum. I don't know where you got your copy of Hoke's book. There are a couple of different versions available on the internet as well as here on the forum. I would encourage you to download one of the versions in my signature line. It includes a lot of corrections to the original scanned version on this forum as well as an introduction that discusses some of the safety issues that weren't well known when the book was written. You'll find answers to at least one or two of your questions there.
> 
> Dave



Thanks for your answer. I got my version on the internet and I recently found out it was made available through this forum 
I found your versions of the book today and I will surely get it printed out


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## Palladium (Nov 20, 2014)

I was in a lab here not to long ago where they do quote " Precious metals recovery from a certain industrial market segments". An in house lab to monitor and process the waste stream. It was a whole lot of people way smarter than me in the room. Lab coats, pocket protectors, and letters of the alphabet after each one of their names! I'm there as an associate of a client who doesn't have the first clue to what's really going on but has a knack for connections and making money. We compliment each other well. I ask a question as to why the hell they're doing something that is costing them about an extra 15-20 %. I actually ask him the question twice after he side stepped it and gave me an answer that was nothing short of an answer you would get in politics. Oh you should have seen the look and that guys face when i stepped on his twinky in that room full of folks. I wasn't going to do it that way, Butttttt...... He was one of those that just couldn't resist kicking the cat from pride! So i proceeded to tear his theory apart and went to his lab and showed him how dumb it was to be smart. Guess what! Yep! He went to politicking. It was that simple and nothing really hard about it. The next day i got a phone call from his boss asking me to please not ruffle the feathers of his director of op's, Buttttt..... Would i mind coming in that weekend and meeting with him in the lab for a little show and tell? Compensation included of course. :mrgreen: The stories not meant to reflect on anyone it's meant to show that sometimes you're not the brightest guy in the room and to think so is really closed mined and can put you at a disadvantage. 

Welcome to the forum brother!


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## nickvc (Nov 20, 2014)

I see a possible member who can learn and contribute here.
The welcome was meant and its up to you to make the best of the forum, what you read will be true, what you can add is down to your knowledge but make it real not theorectical unless it really works.
You won't get shot down if you suggest things that make us all think, right or wrong, who knows no one knows it all in this field of chemistry.
Please stick to safe and proper processes, we take safety for us, our family and pets, neighbours and the environment very seriously.
Get your head down and start reading, get stuck ask, we are a family here we just expect certain behaviour to be seen to be followed.


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## Wingedcloud (Nov 20, 2014)

nickvc said:


> I see a possible member who can learn and contribute here.
> The welcome was meant and its up to you to make the best of the forum, what you read will be true, what you can add is down to your knowledge but make it real not theorectical unless it really works.
> You won't get shot down if you suggest things that make us all think, right or wrong, who knows no one knows it all in this field of chemistry.
> Please stick to safe and proper processes, we take safety for us, our family and pets, neighbours and the environment very seriously.
> Get your head down and start reading, get stuck ask, we are a family here we just expect certain behaviour to be seen to be followed.


Noted 
Thanks for you advice, sir.


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## Wingedcloud (Nov 20, 2014)

Palladium said:


> I was in a lab here not to long ago where they do quote " Precious metals recovery from a certain industrial market segments". An in house lab to monitor and process the waste stream. It was a whole lot of people way smarter than me in the room. Lab coats, pocket protectors, and letters of the alphabet after each one of their names! I'm there as an associate of a client who doesn't have the first clue to what's really going on but has a knack for connections and making money. We compliment each other well. I ask a question as to why the hell they're doing something that is costing them about an extra 15-20 %. I actually ask him the question twice after he side stepped it and gave me an answer that was nothing short of an answer you would get in politics. Oh you should have seen the look and that guys face when i stepped on his twinky in that room full of folks. I wasn't going to do it that way, Butttttt...... He was one of those that just couldn't resist kicking the cat from pride! So i proceeded to tear his theory apart and went to his lab and showed him how dumb it was to be smart. Guess what! Yep! He went to politicking. It was that simple and nothing really hard about it. The next day i got a phone call from his boss asking me to please not ruffle the feathers of his director of op's, Buttttt..... Would i mind coming in that weekend and meeting with him in the lab for a little show and tell? Compensation included of course. :mrgreen: The stories not meant to reflect on anyone it's meant to show that sometimes you're not the brightest guy in the room and to think so is really closed mined and can put you at a disadvantage.
> 
> Welcome to the forum brother!


Ahahahaha 
That's one situation I would like to watch 
Thanks for you support, sir !


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## nickvc (Nov 20, 2014)

Wingedcloud said:


> nickvc said:
> 
> 
> > I see a possible member who can learn and contribute here.
> ...



My pleasure.
I look forward to seeing your progress and success 8)


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## Anonymous (Nov 20, 2014)

Welcome winged. Nice to see a well prepared and thought out introduction. It's good to see someone sharing their history. Well done for achieving what you have, I hope that we can help you to add some good practical knowledge to the sound educational study you've done. 

Jon


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## goldsilverpro (Nov 20, 2014)

You'll find that the ratio of art to science is about 10 to 1. Experience to book learning is about the same.


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## Pantherlikher (Nov 20, 2014)

I met a kid fresh out of his $15k course on how cars work and how to become a repair technician. 
He came to me 1 day and asked me how to change the wiper blades on a car. Got to find out he never touched a wrench but knew everything about cars. Asked me to help him learn. Me, learnt from a junk yard on watchin a guy.

Amusing story but welcome and hopefully this will be a humbling learning experience for the better and you become a great asset to the forum. 

A good place to dig in might be working with the google customsearch up top.
Try a search on Hydrometalurjicle thingy you described in your intro. Interesting older posts come up first. Lots of great information and learning experiences hiding in the older posts. 

Good luck and hopefully, we'll all see great pictures of your success.

B.S.
... I'm so smart, I don't need a name, just 2, count em, 2 letters...

Billy Scott and so full of it, my eyes are brown.


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## kurtak (Nov 21, 2014)

I was one of those Attention Deficit Disorder kids (back before they had a name for it) when I was growing up & going through grade school/high school & you could not sit me down in a chair & teach me anything--- consequently my learning suffered in things like reading, writing, math, history, & yes chemistry (a book class in our high school) - lots of D's & F's

On the other hand put me in a shop class Ag class, biology class (lots of time in the school woods) & I was an A - B student so I am good at building & fixing things - many of the above skills (the ones I got D's & F's in) I had to self learn when I got out in the real world & figured out that they were important to being good at what you do with your hands

In my opinion they put way to much emphasis (had to look the spelling of that last word up in the dictionary) :lol: on book learning - had they allowed me more time in the shop when I was in high school I would have figured out the importance of the book learning classes while still in school instead of after - in other word to be good at the physical application you need to have the book understanding to make it work

My point is this - because I think the shoe fits on the other foot as well - you can have all the book learning in the world - but its of little value if you have no practical application to go with it

Example # 1) I can, have & do build electrical automation control panels for fortune 500 & fortune 200 companies & it sometimes blows my mind how much red ink corrections I have to make on the electrical drawings I get & send back to the guys making the drawings that have never built a control panel in their life - they are smart but lack practical application

Example # 2) Chemistry - In High school I got a Big Fat F --- When I found I had a need to apply it (thanks much to this forum) I sat down & learned it --- if my Chemistry teacher could see me now :mrgreen: he hated me --- but then again I was the kid at the back of the room shooting paper spit wads across the room :lol: 

Pics are some of the control panels I have built & the systems they controlled --- I never spent a day in school learning to do this - currently waiting to see if we get the bid on a panel job for an anodizing company that is adding a third line to their existing two lines which I also did panel work on

Kurt


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## maynman1751 (Nov 21, 2014)

Welcome Wingedcloud! You've picked the very best place to learn, but you must be humble and it seems that you are. 8) 
Very impressive Kurt! :shock:
You may want to check out the references that I and other members have posted below their signature lines. A good place to start.


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## kurtak (Nov 21, 2014)

Here is a better pic of the detail in the panels I build

I have gone from growing up on a farm to working as a volkswagon engine rebuilder to working logging & road building & gold mining to finish carpentry & cabinet building to building electrical control panels & now PM refining

I take great pride in the work I do & the fact that I do this kind of work with never a day in a class room after high school & I almost didn't have enough credits to even get a high school diploma 

Don't get me wrong - there is nothing wrong with getting a good education (book education) it's just my opinion the the real education comes when you put your hands on the work & get them dirty :lol: 8) --- more fun to :mrgreen: 

Kurt


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## 4metals (Nov 21, 2014)

> You'll find that the ratio of art to science is about 10 to 1.



I have always said that refining is a mix of art and science and I have taught many a "laborer" to be quite good refiners. Recently I was discussing the processes of refining with a new client and he is a chemist but he has no intention of getting his hands dirty or teaching anyone, as he said that is what I get paid for. I was explaining it to him from the art and science approach and he just couldn't understand it, he just didn't see the process as art.

So in keeping with my business model, I strive to make every person I teach understand and relate to the process involved. So I had to make this smart guy get it.

I chose to discuss accuracy and precision with him. A good refiner has both. He can relate to that because a good analytical chemist has both as well. But here is how I described it to him.

The method of refining that we choose to process a certain type of material provides the accuracy. Because of the specifics of any method there is a limit to how accurate it can be. An example for forum members is Harolds example of eliminating base metals and incinerating after acid leaching. If you do not incinerate, you will still recover a good percentage of the gold but you can likely have losses due to the traces of acid remaining. The method using the incineration produces a more accurate result, or in other terms a better yield, closer to the actual content.

So a good refiner chooses a method that will give him the best shot at good yields. That is what this forum provides, the best methods that are freely discussed in the industry to get accurate results.

But that is only half of it, the second half of the equation is precision. This is the art. This is how skilled you are at performing the tasks at hand, how well you filter, rinse, decant and perform all of the little intermediate steps to refine a lot. If you have good precision, your results and yields are high. If your precision, or technique, is poor your results will suffer even though you are using an accurate method. 

So refining is a combination of science and art, or if you mention this to a guy with letters after his name, accuracy and precision.


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## solar_plasma (Nov 21, 2014)

In german language we have terms of "medical art" as well as of "engineer's art". Criteria are, beyond knowledge, skills, perception, ability of imagination and intuition, also creativity and efficiency.

Accuracy and precision alone may be what a real refining artist himself perceives, what he is performing, but it seems to me, there is more.

But those are of course only some thoughts of a "hobby artist", just like somebody who loves the arts and sometimes drawing a little by himself.


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