Traitement des eaux par l’utilisation des gousses de la plante Moringa Oléifèra

Abstract

Water pollution by organic materials such as dyes, requires the use of high-performance processes. Among the proposed solutions, the adsorption techniques in low cost adsorbents concretely from vegetable waste. It is in this context that this work is fitted. On the one hand, we were more interested in the valorisation of the vegetable waste from the pods of Moringa Oléifèra in the wilaya of Adrar and on the other hand the study of their adsorbent power. The objective of this work is to work out, characterize and evaluate the performances of Biosorbent and activated carbon prepared from the pods of Moringa Oléifèra. The method of studied development of activated carbon is chemical activation by the phosphoric acid followed by a carbonization at 450°C. Characterization analyzes on the two adsorbents showed that they had a low ash content (4,7% for MOBr and 3,14% for MOCA), a low moisture content (5,89% for MOBr and 2,36% for MOCA) and an acceptable values of iodine number (541,37 mg/g for MOCA and 172,62 mg/g for MOBr). The performances of the synthesized adsorbents are evaluated for the removal of dye (methylene blue). In this work, we have found that the adsorption isotherms of the adsorbent / adsorbate systems studied are satisfactorily described by the Langmuir mathematical model where the maximum adsorption capacity of activated carbon is 434,78 mg/g and that of biosorbent is 381,1 mg /g. The adsorption tests showed that equilibrium was established after (5 minutes for MOBr and 30 minutes for MOCA). All the results obtained show that the dye adsorption kinetics on the two adsorbents is well described by the second-order model. The pH of the solution influences the bleaching efficiency. On the other hand, the thermodynamic study shows that the adsorption process is spontaneous and favorable for both adsorbent, exothermic for MOBr and endothermic for MOCA.