You are here:

Metals/Separation of Metals Through Chemical process

Advertisement


Question
Many companies selling metal refining plants( through chemical process) talk about using following chemicals for refining 1 kilo of dore metal.
We received it when we wanted to buy a machine that would separate metals from the powder that contains mixed metals such as copper,tin,lead, aluminium,gold,silver and palladium obtained from printed circuit boards.

Consumables to be used: (For 1kg dore metal)
1 lt HNO3 nitric acid (liquid), 3 lt HCL hydrochloric acid (liquid), 0.70 lt N2H5OH hydrazine hydrate
(liquid) or 2 kg NaHSO3 (powder), 3 kg NaOH sodium hydroxide (liquid or solid), 0.50 lt HN3
ammonia (liquid), 1 kg NH4CONH4 (fertilizer; solid, granules), 1 kg aluminum scrap (thin sheets), 10 lt
water,

what i need to know is how and at what stage exactly ( for which metal recovery ) above mentioned each chemical is used? What are the chemical reactions?
I will be extremely indebted to the help.
Thanks!
Kamal

Answer
It's good that you are wise enough to ask first as some combinations of chemicals that you have listed would surely blow you into another dimension. Since you obviously have omitted to learn chemistry, you can have from me a simple method:  Mix nitric acid into water (not reversed!) to obtain a 50/50 mixture by volume. If you neglect this step you work in vain. Using fume hood, pour slowly the nitric water mixture upon the powder and wait for a red fume to boil. When finished, the liquid nitric is decanted or filtered away and fresh nitric is added. This time as a concentrate (without water). Heat this at 80 Celsius for an hour and then let it cool before decanting or filtering. You have just removed most of the palladium. What remains undestroyed by the nitric acid is gold and platinum group metals along with tin oxide and antimony oxide. The AR aqua regia solution, then dissolves the rest, gold first. WARNING! STRONG AMMONIA AND ALSO AMMONIA SALTS WILL EXPLODE WITH GOLD SALTS OR GOLD OXIDES!

Metals

All Answers


Answers by Expert:


Ask Experts

Volunteer


Christopher Poe

Expertise

The processing/refining of precious metals including chalcogenic ores like tellurides and selenides.

Experience

32 years experience in ore assaying and refining. Presently head chemist and chief refiner of a Philippine metals company.

Publications
Gold Refining Forum

Education/Credentials
Doctor of Geochemical Research

©2016 About.com. All rights reserved.