the surface of OMA is positive. The results (Table 3) show that OMA removes Mo faster than BTB from Mo-BTB binary solution due to the strong interaction between the positive surface of OMA and ionic Mo. The occupation of OMA adsorption sites by MO and BTB molecules and the steric hindrance of adsorbed mole- cules causes the amount of dyes removed from the binary solution be less than the amount removed from the solution of each dye after