Sources of negative charges on silicate clays is/are

• Silicate clays develop negative charges through various mechanisms:
-Exposed crystal edges: The edges of clay crystals often have unsatisfied chemical bonds that can develop negative charges, especially at higher pH levels.
-Isomorphous substitution: This is the most common source of negative charge in silicate clays. It occurs when a lower-valence cation (e.g., Al3+) substitutes for a higher-valence cation (e.g., Si4+) within the crystal structure, creating a net negative charge.
-Anion exchange: While less common than the other two mechanisms, silicate clays can also exhibit some anion exchange capacity, where negatively charged anions are adsorbed onto positively charged sites on the clay surface.