Elimination des métaux lourds et pesticides en solution aqueuse par des matrices argileuses.

Abstract

The objective of this work is the study of the performance of three Algerian clays in the rough; the bentonite of Maghnia, the kaolin of Mila and the clay Djebel Debbagh of Guelma in the elimination of organic pollutants (an insecticide, a herbicide, a fungicid e) and inorganic some lead (II) and cadmium (II) in synthetic aqueous solutions. The physico-chemical characterization of three adsorbants showed that these clays are silicated materials, rich in alumina. The modelling of the kinetics of studied pollutants revealed its conformity with the kinetic model of the pseudo second order for three types of studied clays. The thermodynamics study showed that the process of retention of th e metallic cations is spontaneous and exothermic, while that of the retention of pesticides revealed that this process is not spontaneous, exothermic and that no crucial change is made on the structure of clays. The study of the adsorption of the metallic cations and the pestici des by studied clays showed that the lead (II) and the herbicide have more affinity for the studied supports than the other organic and inorganic pollutants. On the other hand, the capacities of adsorption of the metallic ions are raised that those with pesticides. The effects of some experimental parameters such as pH, temperature and seed agitation were studied, by applying a design experiment. This plan of factorial experiment allows to show the influence of every parameter independently and their dependences. The obtained results show that the best rate of adsorption of herbicide by the bentonite requires a low pH ( pH=2 ), a temperature of 20°C and an average speed agitation of 4 00 rpm. The studies on the adsorption of pesticides and metallic ions showed that it is mainly influenced by the physico-chemical properties of used clays, the results of the tests allowed us to choose the bentonite as the material which presents a capacity raised for the adsorption.