To enhance the adsorption capacity of Cd2+, -NH2 groups were introduced into the rice straw-derived biochar surface by combining nitrification and amination. The batch and continuous Cd2+ adsorption experiments were performed to determine the role of -NH2 groups on the surface of biochar. The physical and chemical characteristics were analyzed for comparison. The results indicated that the adsorption capacity of the modified biochar (BC-NH2) was boosted by 72.1%. The results of continuous adsorption experiments in fixed bed columns showed that the penetration time of BC-NH2 was three times that of original biochar. The adsorption of Cd2+ by BC-NH2 is a spontaneous endothermic chemical reaction, which was obtained by combing sorption kinetics, isotherms and thermodynamic analysis. The Cd2+ adsorption was mainly the complexation between -NH2 group on biochar surface and Cd2+ in solution. Finally, a possible interaction mechanism between Cd2+ and BC-NH2 was proposed.
Keywords: -NH(2)modification; Biochar; Biomass; Cadmium (II) ions adsorption; Mechanism.
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