Adsorption of Cd (II) on Modified Granular Activated Carbons: Isotherm and Column Study

• Published in: Molecules (Basel, Switzerland) Vol. 22; no. 12; p. 2280
• Main Authors: Rodríguez-Estupiñán, Paola, Erto, Alessandro, Giraldo, Liliana, Moreno-Piraján, Juan Carlos
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 20.12.2017; MDPI
• Subjects: Activated carbon; Adsorbents; Adsorption; Cadmium; Cadmium - chemistry; Cations, Divalent - chemistry; Charcoal - chemistry; Chromatography, Liquid; Diffusion; Dynamic tests; fixed bed column; Flow velocity; Functional groups; Hydrogen peroxide; Hydrogen-Ion Concentration; Isotherms; kinetic model; Kinetics; Models, Chemical; modified activated carbon; Oxidation; oxidation treatment; Oxidation-Reduction; Porosity; Solvents; Surface chemistry; Surface diffusion; Surface Properties; Temperature; Thermodynamics; cadmium; fixed bed column; adsorption; modified activated carbon; oxidation treatment; kinetic model
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules22122280

In this work, equilibrium and dynamic adsorption tests of cadmium Cd (II) on activated carbons derived from different oxidation treatments (with either HNO₃, H₂O₂, or NaOCl, corresponding to GACoxN, GACoxP, and GACoxCl samples) are presented. The oxidation treatments determined an increase in the surface functional groups (mainly the acidic ones) and a decrease in the pH (except for the GACoxCl sample). A slight alteration of the textural parameters was also observed, which was more significant for the GACoxCl sample, in terms of a decrease of both Brunauer-Emmett-Teller ( ) surface area and micropore volume. Adsorption isotherms were determined for all the adsorbents and a significant increase in the adsorption performances of the oxidized samples with respect to the parent material was observed. The performances ranking was GACoxCl > GACoxP > GACoxN > GAC, likely due to the chemical surface properties of the adsorbents. Dynamic tests in a fixed bed column were carried out in terms of breakthrough curves at constant Cd inlet concentration and flow rate. GACoxCl and GACoxN showed a significantly higher value of the breakpoint time, likely due to the higher adsorption capacity. Finally, the dynamic tests were analyzed in light of a kinetic model. In the adopted experimental conditions, the results showed that mass transfer is controlled by internal pore diffusion, in which surface diffusion plays a major role.