Sorption of Ammonium Ions onto Natural and Modified Egyptian Kaolinites: Kinetic and Equilibrium Studies

Thermally activated, acid-activated, and acid-leached of thermally activated kaolinites were prepared from the Egyptian ore. The physical and chemical properties were studied using N2 sorption at −196°C, FTIR, SEM, and the total surface acidity. The sorption of ions on the investigated sorbents was controlled with the solution pH, sorbent dosage, and initial concentration of solution. Kinetic and equilibrium sorption at 30°C were employed. Four kinetic models were applied to the kinetic sorption data; pseudo-second-order, Elovich, and intraparticle diffusion models fitted well the kinetic data whereas pseudo-first-order model was less applicable. Elovich parameters refer to physical sorption type of on nonuniform sites and the intraparticle diffusion controls the sorption of by kaolinites to a small extent. The equilibrium sorption data followed Langmuir and D-R models; the negative value of indicates a spontaneous sorption and the mean sorption energy obtained shows also physical sorption. The sorption capacities of nonactivated and activated Egyptian kaolinites towards sorption (10.87–45.45 mg·g−1) were good sorbents as compared with those uptaken by other clays reported in the literature and proved to be more active besides being less expensive and highly available.