Statistical evaluation of pore volume and surface diffusion model in adsorption systems

The Pore Volume and Surface Diffusion Model (PVSDM) was applied to represent the adsorption of malachite green onto bentonite. A detailed analysis of the diffusion parameters was performed and was conclude that the external mass transfer coefficient (kF) was dependent on the operating conditions and ranged from 1.99 × 10−3 to 2.65 × 10−3 cm s−1; the pore volume diffusion coefficient (Dp) was independent on the initial dye concentration and was 6.11 × 10−7 cm2 s−1; and the surface diffusion coefficient values (Ds) increased with the initial dye concentration and ranged from 6.83 × 10−10 to 7.92 × 10−10 cm2 s−1. Also, the relative contribution of superficial diffusion mechanism was increased with the initial dye concentration. Was determinate an optimal global parameter Ds = 7.73 × 10−10 cm2 s−1 was determinate and statically suitable with the Student's t test, χ2 test and the Fisher's exact test. The model was validated using the optimal value of Ds which is valid over the entire initial MG concentration range compared.