Phenol can cause environmental problems due to low biological degradation, high toxicity and long persistence in the environment. Thus, the removal of phenol and its derivatives from water is of great importance. Application of agricultural waste materials has been intensively investigated for many years for adsorptive removal of active pollutants. The objective of this research was to improve the adsorption capacity of rice husk ash by activation with different chemical agents for removing phenol from aqueous solutions. Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller (BET), and field emission electron scanning microscopy techniques were used for characterization, and the modified rice ash husk was compared with the conventional one. Results indicated that the effect of chemical treatment by NH 4 Cl was better than the other tested chemical agents. The BET specific surface area of NH 4 Cl-activated rice husk ash (ARHA) was 543 m 2 /g, and the average pore diameter was 3.24 nm. The isotherm and kinetic studies of phenol removal by ARHA showed that the Langmuir model and the pseudo-second-order equation represented the best fit with the adsorption data. The maximum adsorption capacity of phenol onto the newly activated rice husk ash was obtained from the Langmuir isotherm model, which was 66 mg/g.