Depressants_in_Mineral_Processing_Presentation.pptx

Depressants_in_Mineral_Processing_Presentation.pptx

1. Depressants in Mineral Processing A Comprehensive Overview for Metallurgical Engineering Students

2. Introduction to Depressants in Mineral Processing Depressants are critical reagents in flotation that increase the selectivity of the process by rendering certain minerals hydrophilic, preventing their flotation. This presentation explores the types, mechanisms, and applications of depressants in mineral processing.

3. Mechanisms of Depression 1. Adsorption of hydrophilic species. 2. Blocking collector adsorption sites. 3. Desorption of activating species (deactivation). 4. Removal of hydrophobic sites (desorption/destruction of adsorbed collector). 5. The role of pH and pulp potential in controlling depression.

4. Types of Depressants Depressants can be categorized into three main types: 1. Inorganic Depressants 2. Small Organic Molecule Depressants 3. Organic Polymer Depressants

5. Inorganic Depressants: Cyanide Cyanide is widely used to depress sphalerite, pyrite, and certain copper sulfides in the selective flotation of lead-copper-zinc and copper-zinc ores. It forms stable complexes with metal ions, preventing their uptake by minerals.

6. Cyanide Mechanism 1. Cyanide reduces Cu2+ to Cu+ and forms soluble cupro-cyanide complexes. 2. Cyanide forms ferric ferrocyanide complexes on pyrite, creating hydrophilic sites. 3. Cyanide prevents xanthate adsorption by forming soluble metal xanthate-cyanide complexes.

7. Inorganic Depressants: Zinc Sulfate Zinc sulfate is often used in conjunction with cyanide to enhance the depression of sphalerite. It prevents the activation of sphalerite by copper ions by shifting the equilibrium to favor zinc adsorption.

8. Inorganic Depressants: Sulfur Dioxide Sulfur dioxide is commonly used as a galena depressant in copper-lead separation. It reduces pulp potential and forms hydrophilic surface reaction products that prevent collector adsorption.

9. Small Organic Molecule Depressants Polyamines such as DETA and TETA are used to depress pyrrhotite in nickel ores. These molecules chelate with metal ions, preventing accidental activation of pyrrhotite.

10. Organic Polymer Depressants Organic polymer depressants, such as starch, dextrin, and carboxylmethylcellulose (CMC), are used to depress various minerals. These polymers work by forming hydrophilic layers on the mineral surfaces, preventing flotation.

11. Case Study and Questions Case Study: A plant is experiencing low zinc recovery due to accidental activation by copper ions. Which depressants could be used to mitigate this? Questions: 1. Explain the mechanism of action for cyanide as a depressant. 2. What role does pH play in the effectiveness of sulfur dioxide as a depressant? 3. Compare and contrast the use of inorganic versus organic polymer depressants.