Application of analytical solution of advection-dispersion-reaction model to predict the breakthrough curve and mass transfer zone for the biosorption of heavy metal ion in a fixed bed column

This work aims to apply an analytical solution of the contaminant transport model to predict the sorption's breakthrough curve and mass transfer zone of single component heavy metal ions using green macroalga, Caulerpa lentillifera, in a small scale cylindrical fixed-bed columns. The model was represented in a form of differential equation with two model constants which were diffusion coefficient (D-eff) and linear sorption coefficient (k(p)). The linear isotherm could be well described for the sorption at a lower range of sorbate concentration while the Langmuir isotherm was suitable for a wider range of concentration. The reference set of experiments (with a bed depth of 4 cm and a flow rate of 6 mL/min) were used for calibrating the model to obtain the model constants. The model could be well applied to predict the breakthrough curve of varying bed depth from the reference set of experiments for the sorption of Pb2+ and Cd2+ . However, the model predicts slower breakthrough time than that in the experimental results when the flow rate is changed from the reference set of experiments. Three-dimensional plots and contour plots were generated to analyze the sorption behavior of metal ion in the column. The relationship between bed depth and service time (BDST) obtained from the model in this work is not linear, as often seen in the general BDST model. Both advection and dispersion processes govern the sorbate transport in the column. The mass transfer zone (MTZ) is continuously expanding along with the column length in this study. The relationship between MTZs and bed depth is also not linear. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.