In this research modified Kaolin by Cetyltrimethylammonium bromide is used as an adsorbent for the removal of Reactive Blue 21 from aqueous solutions. Response Surface Methodology was used to study the effect of independent variables, such as Reactive Blue 21 dye concentration (20, 40, 60, 80 and 100 mg/L), time (10, 20, 30, 40 and 50), initial pH (2, 4, 6, 8 and 10) and modified Kaolin dosage ...