Pseudo-second-order kinetic models for the sorption of malachite green onto Tamarindus indica seeds: Comparison of linear and non-linear methods

In this study, the sorption of malachite green, a basic dye onto Tamarindus indica seed was studied by performing batch kinetic sorption experiments. The equilibrium kinetic data were analyzed using the pseudo-second-order kinetic model. A comparison between linear least-squares method and non-linear regression method of estimating the kinetic parameters was examined. Four pseudo-second-order kinetic linear equations were discussed. The coefficient of determination (r(2)), average relative error (ARE) and the chi-square (chi(2)) test were employed as error analysis methods to determine the best-fitting equation. Kinetic parameters obtained from four kinetic linear equations using the linear method differed but they were the same when non-linear method was used. Type 1 pseudo-second-order kinetic model very well represented the kinetic uptake of malachite green by Tamarindus indica seeds while Type 4 exhibited the worst fit. Present investigation showed that the non-linear method may be a better way to determine the kinetic parameters.