This can be interpreted on the
basis of isoelectric point of green algae around pH 4. At a pH lower
than isoelectric point, cell wall functional groups are protonated;
therefore, the adsorption of anionic dye, namely AO7, was simulated
and dye removal was increased. In contrast, at a pH higher
than isoelectric point the cell walls surface becomes more negatively
charged; hence, cationic dye removal, namely BR46 and BB3,
were augmented due to ionic attraction.