The pH of the dye solution plays an important role in the whole adsorption process. To determine the optimum pH, the pH value was changed from of 1 to 11 with fixed initial concentration of dye
(50 mg l1) and contact time (10 min). Fig. 8 shows the percentage of removal rate of RB5 by LiCo0.5Fe0.5O2 nanoparticles depends strongly on pH.