Mechanism, Kinetics and Thermodynamics of Adsorption of Aqueous Chromic Ion on HNO_3 Treated Mesoporous Activated Carbon

摘要

Mesoporous activated carbons(MACs) were prepared and modified with post-oxidation in HNO_3.The resulting carbons were elaborately characterized for pore structural and surface chemicalproperties. The obtained mesoporous carbons possess the typical honey-comb–like pore structurewith widely average pore size (77 ～ 91 nm), and richness in surface oxygenitrogen functionalities.These samples were subsequently applied in the removal of chromic ion, Cr(Ⅲ) from the simulatedor industrial wastewater to understand the roles of pore structural and surface chemical properties inadsorption of Cr(Ⅲ) from acidic waste water. Mechanism, kinetics and thermodynamics ofadsorption of Cr(Ⅲ) on the these carbons were virtually studied based on the experimentalobservation. The results indicated that adsorption of Cr(Ⅲ) on the mesoporous activated carbonsinvolves formation of carboxylate chelate of the hydrolyzed Cr(Ⅲ) ion with endothermic nature andfollows the ion exchange mechanism. The pseudo second order kinetic model with respect to thevacant surface binding sites was found to be the best suitable for representing the adsorption kineticdata. The maximum adsorption capacity on the examined carbon samples increased from 107.10mg/g to 117.00 mg/g with increased temperature from 30 °C to 50 °C. The complexity of theindustrial wastewater was found with no influence on Cr(Ⅲ) adsorption performance of the acidtreated MAC.