Dynamic studies of copper adsorption on mesoporous alginate beads using an integrated approach of fractal-like kinetic reaction and diffusion modeling

The kinetics of Cu(II) adsorption on calcium alginate (AL) beads was elucidated using reaction-based and diffusion models. In the present work, the fractal psuedo first-order kinetic model has been used in combination with the Vermeulen diffusion model. The Cu(II) adsorption parameters were optimized by batch adsorption studies. The AL beads were characterized using field emission scanning electron microscope (FESEM), energy-dispersive X-ray (EDAX), and Brunauer-Emmett-Teller (BET) surface area analysis. BET studies indicated beads to be mesoporous. The combined studies using fractal reaction and diffusion models helped to trace the path of mass transport of the Cu(II) ions from the bulk of the solution onto the surface of the bead and into the porous mass of the beads. The use of the fractal approach enabled us to determine the heterogeneity of the bead surface and hence gave a better insight into the understanding of the sorption phenomenon. The adsorption rate constants calculated using the equations for the "Fractal" and "Classical" adsorption kinetic models were drastically different, thus pointing toward the explicit need to model the data using diffusion kinetic models attributing to surface heterogeneity. Such combined studies may result in a better understanding of the adsorption of Cu(II) on the AL beads.