Isotherm and kinetic studies for sorption of Cr(VI) onto Prosopis cineraria leaf powder: A comparison of linear and non-linear regression analysis

This research investigated the utilization of Prosopis cineraria leaf powder (PCLP) as biosorbent in the removal of Cr(VI) from aqueous solution. The maximum monolayer biosorption capacity of Cr(VI) onto PCLP after 2 h was 10.283 mg g⁻¹ under optimum conditions: initial concentration 10 mg L⁻¹, pH 5, dose 0.4 g L⁻¹ and temperature at 293 K. For equilibrium modeling, two-parameters (Langmuir, Freundlich, Temkin) and three parameters (Redlich-Peterson, Sips and Toth) isotherm models were used to fit the equilibrium data. Kinetic modeling was performed using Lagergren pseudo-first-order, pseudo-second-order, Elovich, Weber-Morris intraparticle diffusion, and Bangham's model. Both linear and nonlinear regression were compared coupled with several error functions to determine the best fit and model parameters were evaluated. The results revealed that nonlinear method best explain the experimental data revealing Temkin (R² = 0.9938) and pseuso-second-order (R² = 0.9935) models as the best-fitted models with lower error functions. Therefore, the present investigation convinced that PCLP could be used as cost effective, efficient and eco-friendly biosorbent to reduce Cr(VI) concentration in aqueous solution.