The results of corn cobs showed the higher adsorption higher adsorption capacities occurred at pH 5.4 for Ni and Cr removal but 6.5 for Zn removal, nickel ions had a better adsorption efficiency giving ion concentrations at 0.002ppm with removal efficiency 99.9%. At the same sequence, concentration of zinc ions after treatment was better at pH 6.5 that found to be 1.73 ppm with the removal efficiency 91.35%. On the other hand, lowest adsorption efficiency was recorded in case of chromium that was about 7.2ppm after treatment (Table 2), with removal efficiency 95.05% (Table 4 and Figure 2).