The potential of waste residue obtained from alum manufacturing process to remove problematic reactive azo dye (Cibacron brilliant red 3B-A) was investigated. Batch adsorption experiments were carried out to find out the effects of contact times, adsorbent doses, initial dye concentrations, and final pH on the adsorption of the dye by both unmodified and neutralized adsorbents. The results of the experiment showed that from initial dye concentration of 50 mg/L, the adsorption of dye was rapid in the first 15 and 30 minutes of contact time and equilibrium is reached in about 90 and 120 minutes for both unmodified and neutralized adsorbents, respectively. About 92% the dye was removed by unmodified adsorbent at its equilibrium contact time and optimum dose of 12 g/L, however, only 68% removal efficiency was obtained for neutralized adsorbent at its equilibrium contact time and optimum dose of 15 g/L. The time required to reach equilibrium is independent of initial dye concentrations in the working range of this experiment. For the neutralized adsorbent, the percentage of dye removal is nearly constant in the initial pH range of 4-9, and the maximum removal of the dye was obtained at initial pH of 3. In the case of unmodified adsorbent, maximum removal of the dye was obtained at initial pH of 2. The equilibrium adsorption isotherms have been examined by applying the Langmuir, Freundlich, Dubinin- Rasdushkevich (D-R), and Temkin models. The experimental results can be best described by the D-R isotherm. Adsorption kinetics of was analyzed using the pseudo first and second order models and the regression results showed that the adsorption kinetics were more accurately described by a pseudo second-order model, moreover, the intra-particle diffusion was not the only rate limiting factor of adsorption of the dye. Key words: Cibacron brilliant red 3B-A, unmodified and neutralized adsorbents adsorption isotherm, adsorption kinetics, and intra-particle diffusion.