Adsorption using activated carbon is found to be a promising technology for the removal of dyes present in wastewater. The carbon prepared from Adenanthera paronina L seeds (APAC5) through chemical impregnation, microwave carbonization, and finally muffle furnace activation found to have a 948 m2 /g surface area. The microwave heating generates highly branched activated carbon with fewer surface functional groups. The batch mode adsorption of Basic Orange 21 (BO21) dye onto APAC5 is studied. The maximum quantity of BO21 adsorbed is 49.17 mg/g under batch mode study for 50 mg/lof initial BO21 concentration. The nonlinear form of mathematical expression describes the kinetic and isotherm models better under batch mode analysis.