Adsorption of Co(II) from aqueous solutions onto rice husk modified by ultrasound assisted and supercritical technologies

Abstract Rice husk was modified by ultrasound assisted (UA) and supercritical CO 2 (SCO 2 ) technologies, to improve its adsorption characteristics regarding to Co(II). The Co(II) adsorption was studied with respect to the pH effect, kinetic curves and equilibrium isotherms. The UA and SCO 2 treatments provided increases of 7 and 4 times in the surface area, respectively. The maximum experimental adsorption capacities were 17.6, 20.8 and 35.0 mg g −1 , for raw rice husk, SCO 2 –rice husk and UA–rice husk, respectively. These results demonstrated that mainly the ultrasound assisted technology was adequate to improve the rice husk characteristics for adsorption purposes.