The axial dispersion model (ADM) was applied to the breakthrough curves data obtained for lead ions removal from aqueous solutions by a natural zeolitic tuff in a lab-scale packed bed column apparatus. The axial dispersion coefficient and Peclet number were determined from simulations at different superficial solution velocities, bed heights, and particle size cuts of the mineral. The axial dispersion coefficient varied from 6.19x10-6 to 8.28 x10-4 m2.s-1 and was found to increase with solution velocity and particle size while decreasing with bed height. The external film mass transfer coefficient was determined for different solution velocities and particle size cuts and was found to be 4.93 x10-5 to 7.85 x10-5 m.s-1, suggesting a considerable mass transfer resistance.