gold recovery from antimony ore stibnite

Gold Recovery from Antimony Ore (Stibnite): Methods and Challenges

Stibnite (Sb₂S₃) is a primary ore of antimony, but it can also contain trace amounts of gold, making it a potential source for gold recovery. Extracting gold from stibnite requires specialized techniques due to the complex mineralogy and the presence of antimony, which can interfere with conventional gold processing methods. This article explores the most effective approaches for recovering gold from stibnite ore.

Understanding Stibnite and Gold Associations
Stibnite often forms in hydrothermal veins alongside other sulfides, including pyrite and arsenopyrite, which may host fine particles of gold. The gold may be either free-milling or locked within the antimony sulfide matrix, requiring careful liberation before extraction. Additionally, antimony’s refractory nature complicates direct cyanidation, necessitating alternative processing routes.

Methods for Gold Recovery from Stibnite

1. Pre-Treatment: Roasting and Oxidation
Since stibnite is a sulfide ore, oxidative pre-treatment is often necessary to break down the antimony matrix and expose gold particles. Roasting at controlled temperatures converts stibnite into antimony oxides (Sb₂O₃ or Sb₂O₄), releasing sulfur dioxide gas. This process also helps oxidize any associated sulfides that may encapsulate gold. However, excessive temperatures can lead to gold losses through volatilization or encapsulation in slag.

2. Leaching Techniques
- Cyanidation After Pre-Treatment: Once roasted, the calcine can be subjected to cyanide leaching. However, residual antimony compounds may still consume cyanide or passivate gold surfaces, reducing recovery efficiency. Adding lead nitrate or other activators can mitigate this issue.
- Thiosulfate or Thiourea Leaching: These non-cyanide lixiviants are less affected by antimony interference and can be effective for refractory stibnite ores containing gold.
- Chlorination Leaching: A less common but viable method where chlorine gas or hypochlorite solutions dissolve gold from pre-treated stibnite concentrates.

3. Flotation and Gravity Separation
If gold exists as coarse particles, gravity methods like centrifugal concentrators or shaking tables can recover free gold before further processing. Flotation may also be used to separate stibnite from gangue minerals, producing a concentrate suitable for hydrometallurgical