A simplified method to estimate kinetic and thermodynamic parameters on the solid-liquid separation of pollutants

The aim of the present study was to propose a simplified experimental-theoretical method for estimating the kinetic and thermodynamic parameters for the solid-liquid separation of pollutants by using kinetic studies with batch reactors, i.e., the removed quantity of dissolved ion as a function of time at different initial concentration. This method was applied to the removal of uranyl ion (UO(2+)(2)) from aqueous solutions onto synthetic manganese oxide (birnessite). The pseudo-second-order kinetics and one-site saturation models were proposed to fit the experimental and calculated data, the fitting parameters being estimated by nonlinear regression, using the least-squares method. For initial concentration range 0.2-11.8 microM, the results showed that the uranyl removal process in dispersed batch reactors can be efficiently modeled by the proposed models. Then, several kinetic and thermodynamic parameters were calculated, such as maximal removed quantity of uranyl, q(r,max), half-removal time, t(1/2), initial rate of uranyl-ion removal, v(0), initial uranyl-removal coefficient, K, maximal rate of uranyl removal, v(0,max), mass transfer coefficient, D(transfer), equilibrium Langmuir constant, K(L), and constant separation factor, K(s). These parameters make it possible to demonstrate that the removal of U onto birnessite is favorable, and that the maximum surface coverage of the uranyl ions represents about 3% of vacant sites in the Mn layer.