An adsorption model explaining and predicting the adsorption phenomena of palladium complex ions over MgO/Al 2 O 3 and CuO/Al 2 O 3 was developed based on the triple layer theory. Wet impregnation or adsorption experiments were conducted to determine the solution variables and some parameters used in the model and to verify the adsorption model. Adsorption of palladium complex ions on pure oxides (Al 2 O 3 , MgO and CuO) and composite oxides (3% and 15% of MgO and CuO on Al 2 O 3 ) was investigated at different solution pH. From the experiments, Pd adsorption capability of pure and composite oxides was influenced by solution pH, type of promoter on the support and concentration of promoter. Overall the results predicted from the triple layer model agreed reasonably well with the experimental data, except in the pH range near the point of zero charge of oxide. The suggested pH value for preparing Pd/MgO/Al 2 O 3 and Pd/ CuO/Al 2 O 3 composite oxides is the pH close to the initial pH of the palladium precursor solution.