Characterization and evaluation of the adsorption capacity of dichromate ions by a clay soil of Impfondo

摘要

This work had as a general objective the evaluation of adsorption capacity of dichromate ions by clay collected in the Impfondo locality. The mineralogy of this soil was determined by X-Ray diffraction, Infrared spectroscopy and differential thermal analysis and thermogravimetry analysis. The geotechnical (Atterberg limits and grain-size distribution) and the chemical properties (chemical composition, CEC, Tamm Fe and Mehra-Jackson Fe) were also studied. The surface properties (specific surface area and zero charge point) were evaluated. The adsorption isotherms and adsorption kinetics were carried out. Impf clay consists mainly of kaolinite, but also illite, quartz, goethite, anatase, rutile and hematite. The particle size distribution corresponds to clay texture and offers the adsorption possibility. The surface properties (CEC, adsorption isotherm, adsorption kinetics, point of zero charge) have permitted to evaluate the adsorption capacity of Impf clay. This study showed that the adsorption isotherm of dichromate can be interpreted by the Langmuir and Freundlich models. Both models are to the extent of acceptability. The Freundlich model was used to calculate the Freundlich constant and the heterogeneity factor. This study made it possible to conclude that the adsorption yield of dichromate on Impfondo kaolinite is low; it increases with the mass of the introduced kaolinite. And at a mass of 0.5 g of kaolinite in 25 ml of dichromate solution, the adsorption sites become saturated and the equilibrium is reached. Following adsorption kinetics, the adsorption of dichromate is described by the second-order model. It was possible to determine the rate constant and the adsorption capacity of equilibrium dichromate ions. The adsorption of dichromate is favored when the pH of the environment is much lower than that of the zero charge point of the kaolinite.