Mathematical Modeling of Batch Adsorption Kinetics of Lead Ions on Modified Natural Zeolite from Aqueous Media

Natural zeolites are evaluated for toxic heavy metal removal in water and wastewater systems. A two-mass transfer resistance model, consisting of the homogeneous solid diffusion model combined with the external mass transfer resistance, was applied to fit the experimental kinetic data of an agitated batch adsorption system, and a parabolic dependence of the driving force on the particle radius was considered. The mathematical model proposed for the batch adsorption kinetics was simulated using the finite difference method. The model has been successfully applied to simulate lead adsorption onto a modified natural zeolite, and the obtained results were well fitted to the experimental data for different initial lead concentrations. In this procedure, internal effective diffusivity as the process parameter was determined for different concentrations of the solution. Using the estimated value for the internal effective diffusivity, a parametric study has been carried out to study the effects of particle size of adsorbent, initial adsorbate concentration, solution volume and the amount of absorbent on the adsorption kinetics. The results showed that the adsorption kinetics follows the pseudo-second-order kinetic model due to its correlation coefficients (R2), suggesting that the lead adsorption process is very fast. Also, an adsorbent maximum capacity of 136.99 mg/g was found, indicating a large adsorption capacity for lead.