The optimum pH for the adsorption of methylene blue dye onto activated carbon is typically around pH 6-7, which is near neutral conditions. At this pH range, the adsorption efficiency is usually the highest.The efficiency of the adsorption process is affected by the pH due to the surface charge of the activated carbon and the ionization state of the methylene blue dye. At lower pH values, the activated carbon surface becomes more positively charged, while methylene blue dye molecules are primarily in their cationic form. This leads to electrostatic attraction between the dye and the activated carbon, enhancing adsorption.At higher pH values, the activated carbon surface becomes more negatively charged, and methylene blue dye molecules may undergo deprotonation, forming anionic species. This can lead to electrostatic repulsion between the dye and the activated carbon, reducing adsorption efficiency.However, it is important to note that the optimum pH for methylene blue adsorption may vary depending on the specific properties of the activated carbon used, such as its surface chemistry and pore structure. Therefore, it is recommended to perform experiments to determine the best pH conditions for a given activated carbon and methylene blue dye system.