Low cost activated carbon was produced by treated rice husk ash for adsorptive removal of Reactive Orange 16. The selection of adsorbents, effect of equilibrium time, adsorbent dosage, concentration of dye, and pH on removal of dye was optimized as rice husk ash, 30?min, 0.25?g/100 mL, 100 mg/L, and 9.0, respectively. The process fits into Langmuir isotherm and Lagergren pseudo-second-order model with rate constant of 0.0216?g/mg?min. The process was statistically optimized and evaluated by face-centered central composite design. The maximum dye was removed (Q(e)?=?13.32 mg/g) at adsorbent dosage of 0.25 mg/100 mL, pH of 11.0, and concentration of dye: 250 mg/L.