Phenomenological modeling and simulation of competitive biosorption of ternary heavy metal systems in a fixed bed column

Abstract

Phenomenological mathematical modeling was applied to describe the dynamic behavior of the biosorption of ternary heavy metal systems in fixed-bed columns. The modeling approach hereby proposed was verified with experimental breakthrough curves of Cu(II) - Ni(II) - Zn(II) systems using as biosorbent the acidified residue of alginate extraction (RAE) from Sargassum filipendula. The applied model allowed to consistently predict the concentration of the three heavy metals competing for the active sites of the adsorbent material through all the column extension. Due to the relative complexity of the mathematical model, the discretization to transform the system of partial differential equations into a system of ordinary differential equations and the utilization of fictional points for the convergence and stability of the numerical solution were described in detail. All the mathematical development is presented in a generic way, thus, helping other researchers to apply the analysis methodology proposed in this study. By analyzing the breakthrough curves, competitive adsorption was observed for the heavy metals Cu(II) - Ni(II) - Zn(II) in the biosorbent used in the experiments. This is highlighted by the occurrence of outlet concentrations of Ni(II) and Zn(II) above the feed concentrations. The observed affinity order of the metallic ions with the acidified biosorbent RAE is Cu(II) > Zn(II) > Ni(II).