Time-responses of concentration of a saline tracer were determined during fluidization by water at 15 degrees C in a column of 191 mm diameter. Mono-component beds contained 1.85 mm glass beads (density 2500 kg/m(3)) or 0.550 mm ceramic spheres (density 3800 kg/m(3)). A binary fluidized bed, containing equal volumes of these two solids, displayed layer-inversion at superficial liquid velocities of 40.5 and 43.5 mm/s at 10 and 20 degrees C, respectively. Saline tracer pulses were injected just above the distributor, at the column centre. The salt concentration at the bed surface was measured at three radial positions for superficial water velocities up to 127 mm/s. Concentration profiles, simulated by computational particle-fluid dynamics (CPFD) with Eulerian-Lagrangian methodology, showed reasonable agreement with the experimental data. An axial/radial dispersion model was also applied for the mono-component and binary fluidized beds.. The axial dispersion coefficients for the glass beads exceed those for the ceramic spheres. Those for the binary bed are less than expected based on the mono-component data, though a maximum appears at the inversion velocity when closed-closed boundary conditions are employed. (c) 2013 Elsevier Ltd. All rights reserved.