Use of rice husk-based porous carbon for adsorption of Rhodamine B from aqueous solutions

This paper complements the previous one (adsorption of Malachite Green). Adsorption of Rhodamine B (RB) by rice husk-based porous carbons (RHCs) and commercial carbons from aqueous medium have been studied. Three samples of carbons prepared by NaOH activation, three samples prepared by KOH activation and two samples of commercial carbons have been used. The adsorption isotherms have been determined after modifying the carbon N3 surfaces by oxidation with nitric acid and hydrogen peroxide and after degassing at 800 °C. Three samples of N series have larger capacity for removing RB from solution compared to that of the tested commercial carbons, and the capacity of commercial carbons for RB is larger than K series. The adsorption capacity of RB on oxidation carbons is increased and the adsorption capacities on carbons with heat treatment are larger than that on oxidation. The adsorption mechanisms have been proposed through studying the effect of adsorption conditions. They are complicated and appear attributable to various factors, including pore size distribution and chemical interactions between the RB and the surface functional groups on the carbon surfaces.