The document outlines the classification of minerals into polar and nonpolar types based on their surface characteristics, impacting their behavior in flotation processes. Nonpolar minerals are hydrophobic and often floatable without chemical agents, while polar minerals are hydrophilic and require modifications for floatability. Surface energy plays a critical role in determining these properties, making understanding mineral classification essential for optimizing mineral processing operations.

1. Classification of Minerals in
Mineral Processing
Understanding Polar and Nonpolar
Minerals, Surface Characteristics, and
Surface Energy

2. Overview of Mineral Classification:
Polar vs. Nonpolar
• Minerals are classified into two types based on their surface
characteristics:
• - **Nonpolar Minerals:** Characterized by weak molecular bonds,
composed of covalent molecules held by van der Waals forces.
• - **Polar Minerals:** Characterized by strong covalent or ionic surface
bonding, interacting strongly with water molecules.
• This classification impacts their behavior in flotation processes,
particularly in terms of hydrophobicity and hydrophilicity.

3. Nonpolar Minerals: Characteristics
and Examples
• Nonpolar minerals have surfaces characterized by relatively weak
molecular bonds. These minerals are inherently hydrophobic, with contact
angles between 60° and 90°.
• Examples include:
• - Graphite
• - Sulfur
• - Molybdenite
• - Diamond
• - Coal
• - Talc
• These minerals have high natural floatabilities and can be floated without
the aid of chemical agents, although their hydrophobicity can be
enhanced using hydrocarbon oils.

4. Hydrophobicity and Floatability of
Nonpolar Minerals
• Nonpolar minerals are naturally hydrophobic due to their surface
characteristics. Hydrophobicity is crucial for their floatability in flotation
processes.
• To enhance floatability, hydrocarbon oils like fuel oil are often used. This is
especially common in the flotation of coal, where increased
hydrophobicity improves the separation process.
• Layered minerals such as molybdenite and talc break to reveal polar edges
and largely nonpolar faces. While generally hydrophobic, they tend to
become less hydrophobic as particle size reduces, affecting their overall
floatability.

5. Polar Minerals: Characteristics and
Examples
• Polar minerals have strong covalent or ionic surface bonding, making them
naturally hydrophilic. This hydrophilicity is associated with high solid
surface energy.
• Examples of polar minerals include:
• - Silicates
• - Carbonates
• - Sulfates
• - Halites
• - Phosphates
• - Oxides and Hydroxides
• - Quartz
• These minerals have higher polarity and surface energy, making them less
floatable without chemical modification.

6. Hydrophilicity and Surface Energy
in Polar Minerals
• The hydrophilicity of polar minerals is directly related to their high surface
energy, which is high relative to the surface energy of water.
• Solid surface energy can be measured using inverse gas chromatography, a
technique used to characterize the mineral surface in flotation systems.
These measurements reveal that mineral surfaces are heterogeneous,
with a distribution of energy sites.
• This understanding of surface energy is essential for modifying the surface
properties of polar minerals to improve their floatability.

7. Subdivision of Polar Minerals by
Polarity
• Polar minerals can be subdivided into various classes based on their
polarity, which affects their surface energy and hydrophilicity.
• The polarity increases from groups 1 to 5:
• - **Group 1:** Includes native metals and weakly polar sulfides.
• - **Group 2-5:** Includes minerals like silicates, carbonates, sulfates,
halites, phosphates, oxides, hydroxides, and quartz, which are strongly
hydrophilic.
• Understanding this classification helps in determining the appropriate
chemical agents to modify their surface properties for flotation.

8. Relationship Between Surface
Energy and Mineral Behavior
• Surface energy plays a crucial role in determining whether a mineral is
hydrophobic or hydrophilic.
• - **High Surface Energy:** Leads to hydrophilicity, making the mineral
water-attractive.
• - **Low Surface Energy:** Leads to hydrophobicity, making the mineral
water-repellent.
• This relationship is fundamental in flotation, where the goal is often to
increase hydrophobicity for better separation.

9. Measuring Solid Surface Energy in
Minerals
• Solid surface energy can be measured using techniques such as inverse gas
chromatography. This technique helps in characterizing the mineral
surface in flotation systems.
• The measurements provide insights into the heterogeneity of mineral
surfaces, revealing a distribution of energy sites that influence their
behavior in flotation processes.
• Accurate measurement of surface energy is vital for optimizing the
flotation process by selecting appropriate reagents to modify mineral
surfaces.

10. Conclusion and Key Takeaways
• Understanding the classification of minerals into polar and nonpolar types
is essential for effective flotation processes.
• Key Points:
• - Nonpolar minerals are inherently hydrophobic and easily floatable.
• - Polar minerals are hydrophilic, requiring chemical modification for
flotation.
• - Surface energy plays a critical role in determining mineral behavior in
flotation.
• Effective management of these properties is crucial for optimizing mineral
processing operations.