Equilibrium, kinetics, and thermodynamics of batch adsorption of Mn(II) ions on blast furnace slag (BFS) and kaolin (KGA)

AbstractThis article describes the discontinuous adsorption of Mn(II) on kaolin from Guelma, Algeria (KGA), and blast furnace slag from Sider, Algeria (BFS), under the effect of various parameters, namely the contact time, the stirring speed, the pH of the medium, the solution temperature, the adsorbent dosage, the solid particle size, and the initial concentration. Also studied were the models of adsorption, namely the isotherms of adsorption, the kinetics of adsorption, and the thermodynamic study of Mn on the examined adsorbents. Characterization tests have indicated that kaolin consists essentially of hydrated aluminum silicate. The BFS is mainly composed of silicates, aluminates, lime, and magnesium oxide. The specific surface areas of kaolin and BFS calculated using the BET were defined at 134.2 and 238.6m2/g. The adsorption rate of Mn(II) on KGA and BFS is better after 50 and 60 min of contact at Vag: 150 rpm; pH: 5.2; Øs: 100 μm; T: 20 °C; Ms: 1 g, respectively. Maximum adsorption capacities are 36.76 mg/g (KGA) and 59.88 mg/g (BFS). Examination of the adsorption isotherms revealed that the Langmuir model is more appropriate to the experimental data (R2 = 0.99). The values of the Freundlich (n), Langmuir (RL), and Temkin (bt) parameters indicate that the adsorption is favorable. The kinetic examination demonstrated that the pseudo-second-order kinetic model is more adopted for the adsorption of Mn(II) on KGA and BFS (R2 = 0.99). Furthermore, the transfer of Mn(II) from the solution to the surfaces of the investigated adsorbents is controlled by external and internal diffusion. The thermodynamic study brought to light that the adsorption processes carried out were spontaneous, exothermic, and less entropic. This work showed that KGA and BFS can be used as low-cost adsorbents for the removal of Mn(II) ions in aqueous media, and BFS has higher affinities for manganese ion adsorption.