The zeta potential of a colloidal system is a measure of the electrostatic potential at the slipping plane or shear plane of a charged particle in a dispersion medium. It plays a crucial role in determining the stability of colloidal suspensions. The zeta potential is influenced by various factors, including the pH of the system.As the pH of a colloidal system changes, the ionization of functional groups on the surface of the colloidal particles is affected. This leads to a change in the surface charge of the particles, which in turn affects the zeta potential. In general, as the pH increases, the zeta potential becomes more negative, and as the pH decreases, the zeta potential becomes more positive.The relationship between zeta potential and pH can be utilized in controlling the stability of colloidal suspensions in the following ways:1. Adjusting the pH to the isoelectric point IEP : At the isoelectric point, the zeta potential is zero, and the repulsive forces between the particles are minimized. This leads to particle aggregation and the destabilization of the colloidal suspension. By adjusting the pH to the IEP, one can promote flocculation or coagulation of the particles, which can be useful in processes such as water treatment or purification.2. Maintaining a high zeta potential: A high zeta potential either positive or negative indicates strong repulsive forces between the particles, which helps prevent aggregation and maintain the stability of the colloidal suspension. By adjusting the pH to a value where the zeta potential is high, one can enhance the stability of the suspension. This is particularly important in applications such as drug delivery, where stable colloidal systems are required for effective therapeutic action.3. Fine-tuning the zeta potential for specific applications: In some cases, a specific zeta potential value may be desired for a particular application. For example, in the case of targeted drug delivery, a slightly negative zeta potential may be preferred to facilitate interaction with positively charged cell membranes. By adjusting the pH, one can fine-tune the zeta potential to achieve the desired value for the specific application.In summary, understanding the relationship between zeta potential and pH is essential for controlling the stability of colloidal suspensions. By adjusting the pH, one can manipulate the zeta potential to either promote or prevent particle aggregation, depending on the desired outcome for a specific application.