The electrokinetic potential of colloidal silica particles in aqueous solution is significantly influenced by the pH of the solution. The electrokinetic potential, also known as zeta potential, is a measure of the electrical charge on the surface of colloidal particles and plays a crucial role in determining the stability and dispersion of colloidal systems.Silica particles have silanol Si-OH groups on their surface, which can ionize depending on the pH of the solution. At low pH acidic conditions , the silanol groups are protonated, resulting in a positively charged surface Si-OH2+ . As the pH increases, the silanol groups start to deprotonate, and the surface charge becomes more negative Si-O- . This change in surface charge affects the electrokinetic potential of the particles.The isoelectric point IEP is the pH at which the electrokinetic potential is zero, and the colloidal particles have no net charge. For silica particles, the IEP typically occurs around pH 2-3. Below the IEP, the particles have a positive charge, and above the IEP, they have a negative charge.As the pH increases further, the electrokinetic potential becomes more negative, leading to increased electrostatic repulsion between the particles. This repulsion helps to prevent aggregation and stabilizes the colloidal suspension. Conversely, at low pH values, the reduced electrostatic repulsion can result in particle aggregation and destabilization of the suspension.In summary, the pH of an aqueous solution has a significant effect on the electrokinetic potential of colloidal silica particles. The surface charge of the particles changes with pH, which in turn influences the stability and dispersion of the colloidal system.