Efficient and recyclable composite beads containing sodium alginate and EGDMA-AN cross-linked polymer for phenol removal: Kinetic and diffusion mechanisms

Abstract

Adsorption, a ubiquitous technique used in the purification of pollutants streams, depends on the development of a suitable adsorbent wherein kinetic, equilibrium and diffusion phenomena are crucial aspects to ensure that the separation process will be feasible. Hence, in this study, an accurate isotherm in conjunction with rigorous kinetic and diffusion models was developed to investigate the adsorption mechanisms through independent equilibrium and transient experiments during the adsorption of phenol. To this end, dual cross-linked sodium alginate (SA)/ethylene glycol dimethacrylate (EGDMA) and acrylonitrile (AN) composite beads were prepared using a relatively simple gelation technique. The synthesized SA/EGDMA-AN composite material was characterized by FTIR, SEM-EDS, BET, TGA, XRD and the swelling factor. Additionally, the equilibrium was described by the Freundlich isotherm and the kinetics by the Langmuir model. The diffusion coefficients were found to be in the range 1.54 × 10-7 to 8.75 × 10-8 cm2·min-1 for bead diameters of 2.5 and 4.0 mm, respectively, which represent an effective diffusion behavior of the sorbent molecules. The synthesized SA/EGDMA-AN composite beads can be easily regenerated and separated from an aqueous solution. After regeneration, the SA/EGDMA-AN composite beads still present high adsorption capacity for up to four cycles of desorption and adsorption. These results led us to propose a suitable SA/EGDMA-AN composite adsorbent and a rigorous modeling approximation with good predictive ability that would guide the design of further separation processes for the removal of phenol in wastewater treatment.