Élaboration assistée par plasma d’air humide des composés hybrides organo-minéraux magnétiques à base de Eichhornia crassipes (jacinthe d’eau) pour la dépollution des effluents issus de l’industrie minière de la Région de l’Est-Cameroun

Abstract

This study deals with the mining pollution in the Eastern region of Cameroon and to the general concern of water eutrophication. Specifically, it is a question of developing bifacial magnetic and amphiphilic organo-mineral hybrids based on the fibers of Eichhornia crassipes (water hyacinth) using humid air plasma. The different materials developed were characterized by X-ray diffractometry (XRD), Fourier transform infrared Spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) as well as a study magnetic properties. The results of the biosorption of two target pollutants (Merbromine and Green Naphthol B) were found to be exothermic with a maximum adsorption capacity varying from 47.2 to 39.1 mg/g and from 36.9 to 30.1 mg/g for Merbromine and Naphthol Green B between 298 and 323 K respectively, according to Liu's thermodynamic model. The pseudo-second order kinetic model is the one that best describes the data obtained experimentally. The elimination rates of 97.8 and 75.1 % were obtained for Merbromine and Naphthol Green B for a contact time of 60 minutes. Degradation by the heterogeneous Fenton process of solutions of Merbromine and Naphthol Green B gave degradation rates of 97.1 % (Merbromine) and 99.7 % (Naphthol Green B) after 60 minutes. The study of the plasma-assisted degradation of these organometallics shows that the adsorption on the surface of the magnetic hybrid composite is the step limiting the degradation process according to Langmuir-Hinshelwood kinetics. The study of the degradation mechanism showed that hydroxyl radicals (HO°) generated concomitantly by plasma and the Fenton reaction are the species which mainly contribute to the degradation of organometallics used as model pollutants. In accordance with the general objective of the thesis, an application to a real mining effluent was made and the results obtained indicate an elimination of all the ions (Hg2+, Pb2+, CN-, Fe3+ et As5+) initially present, proof that the composite developed is effective.