Preparation and characterization of activated carbon from Balanites aegyptiaca seed shell for the removal of 2,4-dichlorophenoxyacetic acid herbicide from aqueous solution

This research investigates the potential of Balanites aegyptiaca (desert date) seed shells, an abundant renewable bio-waste product, as a precursor for producing low-cost activated carbon for the removal of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution via batch technique adsorption. The chemical activation process was carried out using ZnCl2 as an activating agent at 700 degrees C and 1:2 impregnation ratio. The activated carbon was characterized by "Boehm" titration, measurements of pH of the point zero charge, scanning electron microscopy, Fourier-transform infrared spectroscopy and specific surface areas (S-MB) by methylene blue adsorption. The effects of initial herbicide concentration, contact time, solution pH, and solution temperature on the sorption capacity were investigated. Equilibrium data were fitted to the Langmuir, Freundlich, Temkin, Redlich-Peterson, Sips, and Toth models. The highest correlation coefficient (R-2) values were obtained from Temkin model, with values of 0.997, 0.999, and 0.996 at 298.15, 308.15, and 318.15 K, respectively. The enthalpy change (Delta H degrees), entropy change (Delta S degrees) and free energy change (Delta G degrees) were also evaluated. The negative value of.G degrees shows that the adsorption process is spontaneous, and the positive value of Delta H degrees shows the endothermic nature of the process. The experimental data were tested through the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The pseudo-second-order kinetic model was the most fitting to the kinetics data (R-2 > 0.981). Results showed that Balanites aegyptiaca seed shell activated carbon is very efficient for the removal of 2,4-D from aqueous solutions.