i want to know my mistake after adding smb

[olaboz goldsmith]

my name is olaboz . I am new in this forum and I think this is the perfect place for me . am trying to refined a mother board and some cell phones but am having challenging on the final process. I start my process with nitric and water and I get the gold foil floating and I fittered it out . I put in another containers and I had hydrochloric and nitric and it dissolved the gold foil to a pure yellow water and I had my urea and smb but after all I can't see any gold settling all I see is smb settling inside the solution . pls I want to know my mistake . thank you all

 

[4metals]

How much nitric did you add to dissolve the foils after they were in the hydrochloric acid?
How much urea did you add to the solution?
I suspect you have yet to eliminate the nitric completely.
When you added the SMB the free nitric will immediately re-dissolve the gold. You can see the red fume gassing off the liquid if this is happening. But in small quantities it may not be easy to notice.
I suggest you study more of the methods posted on this forum which will help you through your mistakes.
Welcome to the forum.

 

[Topher_osAUrus]

How much nitric did you add to dissolve the foils after they were in the hydrochloric acid?
How much urea did you add to the solution?

4metals, this isn't really an important question, but yet a curiousity I have..

In your experience with AR an urea
Have you ever encountered a new refiner using FAR FAR too much nitric, so the solution is a very strongly oxidizing version of AR (pretty much reverse AR- maybe not even that strong) and when they tried to use Urea, the addition of it only created urea nitrate which then crystallized out of solution, still leaving some free nitric to dissolve the gold when the precipitant was added?

I only thought of this the other day when watching nilered try to recover the urea from his urine and he did such by making urea nitrate which is insoluble in h2o

 

[kernels]

The biggest issue that I see is that from a motherboard and few phones you have almost no chance of seeing any Gold after precipitation. At best it will be the lightest covering on the bottom of a beaker.

You want to start with at least 250g of Gold plated fingers, so you at least work with about 1g of Gold, anything less is very difficult for a beginner to deal with.

 

[4metals]

My experience with urea and refining is to teach people not to use it. Across the board and almost without exception new refiners overuse chemicals. Solving an overuse of one chemical with an overuse of another is like chasing your tail.

While the OP didn't specify how many cell phones or motherboards he was trying to refine the answer that Kernels gave about how little gold comes off a small number of boards makes the most sense. A positive stannous test before followed by a negative stannous test after will tell the whole story.

As usual testing reveals the truth.

 

[Phishin_ca]

I am curious as to why nitric was used first. While I am not sure on the math here, I would say that if nitric and water were used to "free the foils" and then HCL was used to dissolve those foils, there would be a metric ton of nitric acid still in the mix. That would render the SMB useless.

As a newbie, I have to assume I am missing something.

 

[kernels]

He mentioned that he filtered the gold foils out, so likely not a metric ton of Nitric in the final solution, but probably not fully denoxxed anyway. The reality is that with the amount of ewaste he is working with, you will not see a visible color change / precipitation. My experience is that you only really start 'seeing' a precipitation when you are working with concentrations over 0.5g/L

 

[Geo]

When using nitric acid to remove foils, there will almost always be enough residual nitric acid or nitrate left in the foils to completely dissolve said foils with just adding HCl and heating. That should always be the first step in dissolving metal in AR anyway. Add any water needed and then add the HCl. Warm the solution before adding any nitric acid or nitrate. Adding extra nitric acid was most likely a mistake. Learn how to use sulfamic acid. In my experience, often times when the solution has an abundance of nitric acid that needs to be neutralized, the sulfamic acid does not readily react to the warm solution even with vigorous stirring. As the reaction starts and gets cranked up though, it can boil over because with no reaction at the beginning, the logical coarse of action would be to add some more, right?

 

[Lino1406]

Red fume is not necessarily from gold dissolution, rather it is from reduction of HNO3 by SO2 to NO2. About sulphamic acid: best to wait some hour(s) after addition to make sure it completed its task