Colloidali

Colloidali, known in English as colloids, are mixtures in which finely divided particles are dispersed in a continuous medium. The dispersed phase consists of solid particles, droplets, or gas bubbles, while the continuous phase is typically a liquid, but can be another liquid or a gas. Particle sizes generally range from about 1 nanometer to 1 micrometer. Because of their small size, colloidal particles do not sediment rapidly under gravity and exhibit Brownian motion; they can scatter light, giving the Tyndall effect.

Common classifications include sols (solid in liquid, e.g., ferric hydroxide sol), gels (liquid in a solid), emulsions (liquid in liquid, e.g., milk), foams (gas in liquid), and aerosols (solid or liquid in gas).

Stability of colloids depends on interactions between particles. Electrostatic stabilization, steric stabilization, or combinations (DLVO theory) reduce aggregation. Over time, colloids may coagulate or flocculate, causing phase separation; controlled coagulation is also used in water treatment and food processing.

Preparation and processing methods include mechanical dispersion (grinding, milling), precipitation of a dispersed phase from a solution, emulsification, and chemical reactions that form insoluble particles in situ.

Characterization techniques include light scattering, electron microscopy, turbidity measurements, and zeta potential assessment. Colloids have broad applications in foods, medicines, cosmetics, paints and coatings, catalysts, and environmental technologies.