Hello everyone, my research is about leaching of gold from end-of-life printed circuit board by using Fe2(SO4)3 solution and the leachability was approximately 30-40%. Hence, i have some questions to ask.
1. Could these reactions be spontaneous in my solution?
Au + Fe3+ --> Au+ + Fe2+
2Au + SO42- + 2Fe3+ --> Au2SO4 + 2Fe2+
2. If not, in your opinion, what reactions might occur in my solution for gold leaching?
Presumably this is an aqueous solution. You do not mention pH of the solution, nor do you mention concentrations. Ferric iron can be an oxidizing agent. These types of reactions are best seen with a Pourbaix (Eh-pH) diagram. These diagrams are calculated using a form of the Nernst equation. They are also called phase stability diagrams. In aqueous solutions, they indicate the predominant chemical species for a given pH, oxidation-reduction potential and concentration. Online, look for:
Wikipedia - Pourbaix diagram
Iron or Iron-Sulfur Pourbaix
Gold or Gold-Sulfur Pourbaix
Sulfur Pourbaix
Thomas Wolke First of all, I'm incredibly thankful for your answer and suggestion and i will read the data you suggested. For information that I forgot to describe, i used 15 g/L of Fe2SO4 conc. After 1 h, the result found that system pH was around 1.9-2.1 and ORP was approximately 550 mV.
Reaction (1) takes place in the opposite direction:
Au+ + Fe2+ = Au + Fe3+
and is used, inter alia, to precipitate gold from aqua regia solutions.
Dear Natrawee Khetwunchai thank you for your very interesting technical question. Please find cited below some research articles in which the mechanism of gold leaching using Fe2(SO4)3 has been investigated:
1. Recovery of Gold from the Refractory Gold Concentrate Using Microwave Assisted Leaching
(see attached pdf file)
2. Bacterially generated Fe2(SO4)3 from pyrite, as a leaching agent for heavy metals from lignite ash
Article Bacterially generated Fe2(SO4)3 from pyrite, as a leaching a...
This article is freely available as public full text on ResearchGate.
3. Leaching kinetics of gold bearing pyrite in H2SO4−Fe2(SO4)3 system
(see attached pdf file)
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