Adsorption of Cobalt onto Graphite Nanocarbon-Impregnated Alginate Beads: Equilibrium, Kinetics, and Thermodynamics Studies

Abstract

A novel adsorbent was developed impregnating graphite nanocarbon (GNC) into alginate beads (AB) for efficient cobalt (Co(II)) removal from an aqueous solution. Physicochemical and spectroscopic properties of graphite nanocarbon-impregnated alginate beads (ABGNC) were characterized and compared with those of AB. Co(II) adsorption on ABGNC was quantitatively evaluated by determining kinetics and thermodynamics parameters. The Co(II) adsorption capacity onto ABGNC was highest at neutral pH condition. Increasing the temperature from 288 to 318K resulted in a 2.5-fold higher Co(II) adsorption onto AB, while thermal dependence of Co(II) adsorption on ABGNC was not found. Kinetic studies showed an applicability of the pseudo-second-order kinetic model for both AB and ABGNC. Monolayer adsorption was the dominant mechanism of Co(II) adsorption on both AB and ABGNC. Thermodynamic studies revealed that Co(II) adsorption was an endothermic and spontaneous process. Positive values of entropy indicate randomness in solid/aqueous phases, and mean free energy (E-a) fits in the range of chemisorption.