Colloids are heterogeneous systems composed of particles (distributed phase) broken down into microscopic particles (dispersion medium). Colloidal particles have a significant surface area/unit mass due to their small size. Their scattered phase is larger than genuine solutions but a lower size than suspension. As a result, they have distinct properties.
A colloidal system is a complex homogeneous particle in which particles are distributed uniformly throughout the fluid and it depends on the dispersion medium and dispersed phase’s state: solids, liquids, or gases.
There are eight different types/states of colloidal systems. We can divide colloids into eight groups based on the phase of the dispersion medium and the dispersed phase:
Colloidal systems are classified into the following categories:
Amphiphiles, also known as related colloids, are surface-active agents with a hydrophilic head and a lipophilic tail. Amphiphiles exist clearly and in a sub-colloidal size range when present in a liquid at low concentrations.
Multimolecular colloids are made up of numerous atoms or tiny molecules (diameter 1 nm). These colloids are typically lyophobic. As an example, consider gold and sulphur sols.
Weak Van der Waal interactions hold small molecules (or atoms) together. Therefore, these colloids are typically lyophobic. This implies that these colloids have little or no attraction forces with the dispersion medium.
The molecules in macromolecular colloids have sizes and dimensions similar to colloidal particles (100 nm). Proteins, starch, and cellulose are a few examples of colloids that are comparable to actual solutions:
Dispersible particles of multimolecular colloids are held together by Van der Waals forces. As an example, consider gold sol, sulphur sol, and so on.
A gold sol may have particles of varying sizes of multiple gold atoms. Sulphur sol, for example, is made up of particles that have a lot of S8 molecules.
The dispersed phase particles in this colloid are large enough to have a colloidal dimension. These molecules are known as macromolecules because they have an extremely high molecular mass. Colloidal solutions generated when such compounds are dispersed amidst the best suitable dispersion media are macromolecular colloids.
The majority of lyophilic sols are macromolecular colloids.
Natural macromolecules include starch, proteins, gelatin, cellulose, nucleic acids, etc. Synthetic polymers, such as polyethene and synthetic rubber, are examples of created macromolecular colloids.
Some compounds act as colloids at high concentrations due to aggregation formation. At low concentrations, however, they operate like regular strong electrolytes. Moreover, the micelles are the aggregates that form due to this process, and such colloids are referred to as linked colloids.
A colloid is used to thicken industrial items such as toothpaste, lotions, lubricants, coatings, etc. In addition, colloids are important in the production of paints and inks. For example, the ink used in ballpoint pens is a gel (liquid-solid colloid).
Here are a few more examples:
In this article, we have investigated the colloids classification system, which consists of eight varieties of colloids based on dispersion phase and dispersion medium. The definitions and examples of lyophilic colloid, lyophobic colloid, macromolecular colloid, multimolecular colloid, and allied colloids were examined.
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