Question

How do colloidal particles develop electrical charges on them?

Explain the origin of electrical charge on colloidal particles.

Answer 1

Colloidal particles develop electrical charge mainly by three mechanisms: (a) dissociation of adsorbed molecular electrolytes on their surface, which ionize and leave a charge on the particle; (b) dissociation of molecules forming the colloidal aggregates, such as soap molecules that ionize and aggregate, carrying charge; and (c) preferential adsorption of ions from the surrounding solution, where particles adsorb ions common to their lattice, imparting positive or negative charge. For example, ferric hydroxide particles adsorb Fe³⁺ ions, becoming positively charged, while AgCl sol particles adsorb Cl⁻ ions, becoming negatively charged.