COLLOIDAL
DISPERSION
by Ayesha Ahmed
Background
•• Colloids are heterogeneous systems
appearing homogeneous to naked eye
•• Particle size ranges from 1 nm to 1000 nm
•• Colloidal chemistry bridges true
solutions and suspensions
Basic Terminology
•• Colloid: System containing
dispersed particles
•• Dispersed Phase: Substance in
colloidal form
•• Dispersion Medium: Continuous
phase
•• Examples: Milk, fog, paint
Classification
Based on Physical
State
•• Solid in Liquid: Sol (e.g., paint)
•• Liquid in Liquid: Emulsion (e.g., milk)
•• Gas in Liquid: Foam (e.g., shaving
cream)
•• Solid in Gas: Aerosol (e.g., smoke)
Classification
Based on
Interaction
•• Lyophilic colloids: Solvent-loving,
stable
•• Lyophobic colloids: Solvent-hating,
unstable
•• Association colloids: Form micelles
above CMC
preparation of colloids (physical method)
•Dispersion methods: Grinding, milling
•• Peptization: Conversion of precipitate into colloid
•• Electrical dispersion (Bredig’s arc method)
Preparation of colloids (chemical method)
•• Reduction: Formation of metal sols
•• Oxidation reactions
•• Hydrolysis of salts
•• Double decomposition reactions
Kinetic properties
Optical properties
Electrical properties
•Brownian motion
prevents settling
•Tyndall effect confirms
colloidal nature
•Electrophoresis:
Movement of particles
•Light scattering depends
on particle size
•Electro-osmosis:
Movement of medium
•Used in ultramicroscopy
•Coagulation by
electrolytes
•Diffusion ensures uniform
distribution
•Sedimentation occurs
slowly under gravity
Importance in Modern Science
•• Basis of nanotechnology
•• Used in drug delivery systems
•• Environmental and industrial importance
Applications of Colloidal
Dispersions
•• Water purification and sewage treatment
•• Food industry: Milk, butter, ice cream
•• Pharmaceutical formulations
•• Paint, rubber, and textile industries
Purification of Colloids
•• Dialysis: Removal of electrolytes
•• Electrodialysis: Faster purification
•• Ultrafiltration
Conclusion
•• Colloidal dispersions are vital chemical systems
•• Properties depend on size and interactions
•• Wide applications in daily life and industries
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