Determination of axial dispersion and overall mass transfer coefficients for Ni (II) adsorption on nanostructured γ-alumina in a fixed bed column: experimental and modeling studies

In this study, nanostructured gamma-alumina is used as an adsorbent for the removal of nickel from aqueous solutions using a fixed-bed column and batch experiments. Different parameters, including the initial nickel solution concentration, contact time, and pH were analyzed to determine their optimum values. The results showed that adsorption efficiency increased as contact time increased; optimum contact time was observed to be 150min. The efficiency of removing metal ions from an aqueous solution increased as pH increased from 2.5 to 4.5, but decreased as pH rose higher, thus, optimum pH was determined to be 4.5. The Langmuir isotherm model showed better agreement with the experimental data than the Freundlich and Tempkin isotherm models. The maximum capacity of the adsorbent in the Langmuir equation was 78.74mg/g. In the present study, adsorbent bed performance breakthrough curves for different adsorbent bed heights, influent flow rates, and concentrations were analyzed. The experimental data showed an increase in adsorption capacity at lower flow rates and higher influent concentrations and bed heights. To solve the bed equations, the lumped method was used to predict the breakthrough curve and model overall mass transfer coefficient (K-overall) and axial dispersion coefficient (D-z) parameters to compare with experimental results.