Caractérisation de biomatériaux à base de déchets agricoles en vue de l'élimination des polluants en solutions aqueuses

Abstract

This thesis focused on the valorization of local plant biomass, in the raw state and after chemical treatment with H3PO4, as economic and ecological adsorbents for the treatment of water contaminated with toxic dyes. Turnip leaves (TL and TLA) were used for the elimination of crystal violet CV, pumpkin peels (PP and APP) for congo red CR, and pomegranate crusts (PC and APC) for methyl red MR. The prepared adsorbents are characterized by several methods such as: XRD, textural analysis by, FTIR, TGA / DTG and SEM. The adsorbents were subjected to various elimination tests for crystal violet (CV), congo red (CR) and methyl red (MR) dyes under different experimental conditions: contact time, temperature, pH, initial dye concentration and adsorbent dose. The adsorption of the dyes by the different materials increases with the contact time. The pseudo-second-order kinetic model proved to be the most suitable for describing the dynamic adsorption process on TL, TLA, PP, APP and APC powders, while Elovich's model described the behavior of the PC adsorbent well. Regarding the adsorption isotherm, the Sips model showed the best fit for TL, TLA, PP, APP and APC. On the other hand, for the PC material, it is the Langmuir model which has proved to be the most suitable, with maximum adsorption capacities (q_max) of 635.54 mg/g, 621.76 mg/g, 265.52 mg/g, 698.20 mg/g, 55.74 mg/g and 7.39 mg/g respectively. Thermodynamic studies have demonstrated that the process of adsorption of dyes (CV, CR, MR) on our biomass is spontaneous and exothermic. In conclusion, this study demonstrated that agricultural waste constitutes effective adsorbents for the elimination of anionic (CR, MR) and cationic (CV) dyes, thus offering a promising solution for the treatment of contaminated industrial water. It should be emphasized that the biomasses chemically activated with H₃po₄ have adsorption performances superior to those of the crude biomasses.