shows that the color removal was maximum and unaffected when the initial pH of the dye solution was in the range 3–10, and thus the pH of the system (dye solution + metal hydroxide sludge) remained 8.6±0.3. The sludge may contain some buffer that can resist the pH change of the aqueous system if the amount of acid or base in solution is not high. The final pH of treated water, after adsorption and separation of the precipitate, was found to be 7–8. At an initial solution pH below 3 or above 10, the color removal decreased and the optimum system pH (pH 8–9) could not be maintained. This indicates that excess amount of acid or base in solution reduces the adsorption efficiency of metal hydroxide sludge. Generally, metal hydroxides are amphoteric, the lower capacity in adsorption may be due to the solubility of metal hydroxides in strong acid or base [18]. However, metal hydroxide sludge can be easily applied in a wide range of initial pH values, without pH adjustment.