Methods and Processes for Removing Cyanide from the Surface of Sulfide Ores

Cyanidation leaching is a widely used process in the gold mining industry. However, cyanidation leaching tailings often pose significant challenges. These tailings typically contain low - concentration cyanides, unextracted gold and silver, as well as carrier minerals such as chalcopyrite and pyrite. The surfaces of sulfide ores in these tailings are inhibited by Sodium cyanide during the cyanidation process. Although the ore grade is low and the cyanide concentration is not extremely high, the large volume of tailings makes them a major concern.

Currently, there are three common treatment methods for cyanidation leaching tailings: acid activation, oxidant activation, and copper - salt treatment.

Acid Activation Method

The acid activation method involves adding sulfuric acid or oxalic acid to activate the tailings. While this method can effectively activate the tailings, it has several drawbacks. Firstly, it is prone to generating toxic and harmful hydrogen cyanide gas. Although the recovered hydrogen cyanide gas can be reused, the operation poses a high risk. Secondly, the acidic environment can easily corrode equipment and pipelines, requiring high - level anti - corrosion measures.

Oxidant Activation Method

In the oxidant activation method, hydrogen peroxide or hypochlorite is added to activate the tailings. However, it is difficult to precisely control the dosage of the oxidant. Slightly excessive amounts can oxidize sulfide ores, reducing their recoverability. Moreover, many oxidants are corrosive to the human body, posing a potential threat to the health of workers.

Copper - Salt Treatment Method

The copper - salt treatment method uses inorganic salts such as copper sulfate or iron salts to activate the tailings. Nevertheless, environmental regulations have strict requirements for the discharge of copper ions in wastewater. Additionally, copper ions are activators for sphalerite and pyrite. Therefore, this method is not suitable for cyanidation tailings that contain both sphalerite and pyrite, and it is not environmentally friendly.

In conclusion, the treatment of cyanidation leaching tailings presents a complex set of challenges. Despite the relatively low cyanide content, the high investment costs and strict safety and environmental requirements make it necessary to explore new, more effective, and sustainable treatment methods. This could potentially involve a combination of existing techniques or the development of entirely new approaches to address the environmental and economic concerns associated with these tailings.