1. Electrostatic Metal Separation

  • Principle: Utilizes differences in electrical conductivity to separate conductive metals from non-conductive materials under an electric field.
  • Applications:
    • Recycling of waste cables and electronic waste.
    • Separation of plastics and metals.
  • Advantages:
    • High efficiency for separating fine materials.
    • Effective for non-ferrous and mixed materials.
  • Limitations:
    • Requires materials to be dry and finely processed.

2. Magnetic Separation

  • Principle: Leverages magnetic force to extract ferromagnetic metals like iron and steel from mixtures.
  • Applications:
    • Steel recycling.
    • Separation of ferrous components from electronic waste.
  • Advantages:
    • Simple and efficient.
    • Suitable for high-volume processing.
  • Limitations:
    • Only works with ferromagnetic metals.

3. Eddy Current Separation

  • Principle: Uses eddy currents induced by a magnetic field to separate non-ferrous metals (e.g., aluminum, copper) from other materials.
  • Applications:
    • Recycling aluminum, copper, and zinc.
    • Commonly used in e-waste and appliance recycling.
  • Advantages:
    • Effective for non-ferrous metals.
  • Limitations:
    • Less effective for small or thin metal particles.

4. Dense Media Separation

  • Principle: Relies on density differences, using a heavy medium (e.g., water mixed with barite) to separate materials.
  • Applications:
    • Ore processing.
    • Metal recovery from electronic waste.
  • Advantages:
    • High precision, ideal for fine particles.
  • Limitations:
    • High energy consumption and complex equipment.

5. Wet Separation

  • Principle: Separates materials by their density and solubility differences in a liquid medium.
  • Applications:
    • Recycling metals from waste circuit boards and cables.
    • Extracting rare and precious metals.
  • Advantages:
    • Precise separation of multiple metals.
  • Limitations:
    • Expensive chemicals and potential environmental impact.

6. Airflow Separation

  • Principle: Utilizes air velocity and density differences to separate lightweight materials from heavier metals.
  • Applications:
    • Separating metals from plastics.
  • Advantages:
    • Contact-free method for lightweight debris.
  • Limitations:
    • Less effective for lightweight metals like aluminum.

7. Froth Flotation

  • Principle: Differentiates materials based on their hydrophobicity or hydrophilicity in a liquid containing surfactants.
  • Applications:
    • Separating metals from resin in circuit boards.
  • Advantages:
    • Effective for separating fine particles.
  • Limitations:
    • Requires chemical treatments and has environmental concerns.

8. Mechanical Crushing and Screening

  • Principle: Materials are crushed into smaller particles, then separated by size using vibratory or screening equipment.
  • Applications:
    • Preliminary processing of appliances and e-waste.
  • Advantages:
    • Widely used and mature technology.
  • Limitations:
    • Limited to rough separation.

9. Infrared/Laser Sorting

  • Principle: Differentiates materials by analyzing their spectral characteristics using infrared or laser technology.
  • Applications:
    • Separating metal impurities from plastics.
  • Advantages:
    • High precision and non-contact.
  • Limitations:
    • High cost and requires clean input materials.

10. Chemical Separation

  • Principle: Uses chemical reagents to selectively dissolve specific metals or non-metals for separation.
  • Applications:
    • Recovery of rare and precious metals (e.g., gold, palladium).
    • Metal extraction from waste batteries.
  • Advantages:
    • Effective for high-value metals.
  • Limitations:
    • Complex chemical handling and waste treatment.

Combining Techniques

These methods are often used in combination. For example:

  1. Mechanical crushing is used as a preliminary step.
  2. Followed by magnetic separation, eddy current separation, or electrostatic separation for fine classification and recovery.