refining :method whit nitric acid -the problem.

[[email protected]]

I would like to communicate my experience.

What I have available: Motherboards Video connectors adapters, drive adapters, ram, cpu
I remove the battery if present and capacitors.
cut into pieces motherboards (20 x 20 cm.)

phase 1) nitric acid 65% and demineralized water in proportion 50% demineralised water and 50% nitric acid.
It immerses all the electronic equipment and after 1- 2- days filter the liquid.I wash very carefully tabs, wash and rinse carefully all the components on the bottom.

Sometimes the liquid is blue and sometimes green.
the material retained in the filter (whitish sludge, a lot of sand and of course tiny gold).

Phase 2) ACQUA REGIA. immerse in acqua regia all the mud obtained from step 1 (50 ml of nitric acid 65%, and 150 ml of muriatic to 30%).
the solution becomes sometimes very intense yellow and sometimes olive green.
After 12-24 hours the solution filter on paper filter and the solution is colored a beautiful yellow.

add approximately 15- 20 g technical urea
add powdered smb
Add almost boiling demineralized water to facilitate the dissolution of the smb.
The liquid remains yellow but after 20-30 minutes begins to separate and change color (brown)
my problem is: precipitation is white sand and little brown.

Using this method because except in the first step the sludge (and gold) and second phases throw mud and keep the liquid. motherboards and all connectors come out after treatment
perfectly clean.

it would be right to do after the stage 1 and before to put in acqua regia ,washing by boiling in water for 5 minutes to filter and repeat three times,
and wash with muriatic acid (boil for 5 minutes) and repeat three times?
better to make an even wash with ammonia.

many thanks for your suggestions.

 

[nickvc]

The White powder in your filter is caused by you not removing the tin first by using HCl, it is stannic acid, tin dissolved in nitric which can and will hold some values, to recover the values you need to dry the White powder and incinerate them and them use HCl to remove the tin, as one further note if you have any palladium in the mix or silver it will now be in your nitric solution.
There are many threads on how to process most scrap items I suggest you do some reading and research before continuing, it might well save your , time, money and lots of frustration.

 

[patnor1011]

What you described is not economically viable. While you may get some gold in form of pieces of foils you are going to lose most of it unless you dissolve every last bit of metal present in solution. No matter how carefully you wash remaining metal which appears to be stripped if it will not be dissolved completely you are going to lose gold.
Gold recovery from motherboards cant be done the way you described it unless you are happy with partial recovery and getting only some of what is in there and even that will require tremendous amount of work and chemicals - you just experienced it yourself.
You need to cherry-pick only good stuff and process it accordingly.