# Precipitation problem



## umer (Nov 6, 2021)

I have some smartphone waste, and removed their boards add some HCl to remove Sn on boards, and applied nitric acid to solve copper and silver, then used AR to dissolve gold, when I come to precipitation process, I added urea to remove excess of nitric then add SMB powder to precipitate but nothing happened. 

Can u tell me is there anything I did wrong, or of there is a better method for mobile phone waste let me know


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## nickvc (Nov 6, 2021)

If you left any HCl on your boards and then added nitric what little gold that was there may well have dissolved and be in your nitric solution, to confirm this and or how to find your gold would be to test with stannous.


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## umer (Nov 6, 2021)

nickvc said:


> If you left any HCl on your boards and then added nitric what little gold that was there may well have dissolved and be in your nitric solution, to confirm this and or how to find your gold would be to test with stannous.


I am a newbie for this inorganic processes, I have the nitric solution and the Sn solution, have I do check if there is gold in them, can u help me


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## umer (Nov 6, 2021)

Btw, I did hot water washing after each chemical exposure


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## ZiegenSauger (Nov 7, 2021)

Based on the information given, my first remark is about volume/weight/amount of source material being processed. To illustrate, you could have done everything perfectly well and correct, however today's eWaste yield is so so so much low that you would've dropped one "grain" of gold. You would need a microscope to see.
If you have well over 500 grams of smartphone everything useful (mid to high grade, gold covered circuit boards, speakers, connectors, antennas, well, everything that yields gold from smartphones, you would expect to get 5g of gold in an approximation scenario. Do you know what is the weight and loose classification of your source material?

Since you mentioned your have recently started, it is very common to stack a lot of computer, tablet, phones, games, other electronics, sort everything out, see a bowl full of pins, poles, molex, flex, fingers, connectors, and other shiny stuff and assume you have a half ounce of gold from those 50 different devices you collected from friends, family, and neighbours.

Not really.

Assumed lot's of things, let me know your specifics to see if I can help

Cheers mate


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## umer (Nov 8, 2021)

ZiegenSauger said:


> Based on the information given, my first remark is about volume/weight/amount of source material being processed. To illustrate, you could have done everything perfectly well and correct, however today's eWaste yield is so so so much low that you would've dropped one "grain" of gold. You would need a microscope to see.
> If you have well over 500 grams of smartphone everything useful (mid to high grade, gold covered circuit boards, speakers, connectors, antennas, well, everything that yields gold from smartphones, you would expect to get 5g of gold in an approximation scenario. Do you know what is the weight and loose classification of your source material?
> 
> Since you mentioned your have recently started, it is very common to stack a lot of computer, tablet, phones, games, other electronics, sort everything out, see a bowl full of pins, poles, molex, flex, fingers, connectors, and other shiny stuff and assume you have a half ounce of gold from those 50 different devices you collected from friends, family, and neighbours.
> ...


I had 143 gr of pcb only, I seperated other parts for some other processes, used only pcbs and I know there not much gold in it but I did not have any precipitate at the end, I do this small portions to be sure the process then I move bigger amounts, I have limitless amount of waste phones and computers.

As I watched a YouTube video they had partials had could be seen by eye from 100gr of pcbs. But I couldnot. 

As they state before, when I add nitric could I be dissolve all the gold with silver, if I did, is there a process I can reacquire them.


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## Yggdrasil (Nov 8, 2021)

Nitric will not dissolve gold.
As long as there are no chlorides to make a minute amount of AR.
If there are Chlorides present, any silver dissolving in Nitric will create undissolvable AgCl.
And the solution will be white to hazy green/yellow/blue depending on the colour of the solution itself.


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## ZiegenSauger (Nov 9, 2021)

umer said:


> I had 143 gr of pcb only, I seperated other parts for some other processes, used only pcbs and I know there not much gold in it but I did not have any precipitate at the end, I do this small portions to be sure the process then I move bigger amounts, I have limitless amount of waste phones and computers.
> 
> As I watched a YouTube video they had partials had could be seen by eye from 100gr of pcbs. But I couldnot.
> 
> As they state before, when I add nitric could I be dissolve all the gold with silver, if I did, is there a process I can reacquire them.


Got it my friend. Now, what PCBs you have? Have you sorted them out? Are you 100% sure all of them have a full gold layer?
Even so, let's use those videos you use as example, their recovered buttons is what? One gram or less. Haven' t you missed the little precipitation?
You get a grasp in similar scenarios after long practice and merge with the process of capturing small amounts. Often times is there, either floating and you are not having a visual impact. Or the color of everything is paralaxing your vision. I am able today to get miniscule amounts, but I am quite precise on estimating, sometimes I save the final impregnated AR when stannous shows questionable amounts (then I use the same AR when I have more recovered gold, sometimes i have to reuse 2 or 3 times to have a decent good presence to precipitate.

I dare to say you are experiencing the same initial challenges I did. Save whatever you have in a safe temporary container and revisit later.


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## umer (Nov 9, 2021)

ZiegenSauger said:


> Got it my friend. Now, what PCBs you have? Have you sorted them out? Are you 100% sure all of them have a full gold layer?
> Even so, let's use those videos you use as example, their recovered buttons is what? One gram or less. Haven' t you missed the little precipitation?
> You get a grasp in similar scenarios after long practice and merge with the process of capturing small amounts. Often times is there, either floating and you are not having a visual impact. Or the color of everything is paralaxing your vision. I am able today to get miniscule amounts, but I am quite precise on estimating, sometimes I save the final impregnated AR when stannous shows questionable amounts (then I use the same AR when I have more recovered gold, sometimes i have to reuse 2 or 3 times to have a decent good presence to precipitate.
> 
> I dare to say you are experiencing the same initial challenges I did. Save whatever you have in a safe temporary container and revisit later.


I do have smart phone pcbs and I sorted them well, I guess. 

At the end of AR precipitation reaction, I was expecting a colour change in solution, but I did not happen. I just had some small particles and they dissolved back. And I get nervous, made a mistake of adding to much SMB. Now that solution has a layer of white precipitant. 

Also I save all end solutions, nitric and first HCl solutions, moreover waters that I wash my sample each step, so I can check them when I have enough knowledge about gold refining. 

I have a bioengineering back ground, so I do know how to handle and use things. But my specialist is not inorganic chemistry, mine is organic chemistry. So I try to learn more and more on this topics then I do efficient reactions and get more accurate results.


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## Dougplogan (Jan 3, 2022)

umer said:


> Btw, I did hot water washing after each chemical exposure


The first time I did cell phone boards I dessolved tin with hydrochloric acid and when I went to rinse the boards off. I grabbed the wrong container that had tap water in it. Even though I was only rinsing them off all my gold plating changed colors and revealed the copper under them. Basically the chlorine in the water was mixing with tiny amount of HCl on the boards washing away the gold. Very very tiny amount of plating on cell phone circuit boards


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## Dougplogan (Jan 3, 2022)

umer said:


> I have some smartphone waste, and removed their boards add some HCl to remove Sn on boards, and applied nitric acid to solve copper and silver, then used AR to dissolve gold, when I come to precipitation process, I added urea to remove excess of nitric then add SMB powder to precipitate but nothing happened.
> 
> Can u tell me is there anything I did wrong, or of there is a better method for mobile phone waste let me know


Also a stannous test is necessary. I always check all solutions. It allows you to know where gold is at and not guess or assume


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