Utilisation de nanoparticules et de nanocomposites pour des applications en adsorption et photocatalyse hétérogène dans le visible.

Abstract

This research aims to enhance the optical and photonic properties of pure and doped zinc oxide (ZnO) nanoparticles and evaluate their effectiveness as adsorbent materials for the removal of the organic pollutant, methyl orange. It also involves comparing the performance of ZnO as an adsorbent and a photocatalyst. In this study, manganese-doped ZnO powder was synthesized in our laboratory using the sol-gel method. The resulting powders were calcined at room temperature for 24 hours to obtain pure phases. The degradation and photodegradation of methyl orange were then studied using pure ZnO and ZnO doped with different percentages of manganese (2%, 4%, 6%, 8%, and 10%). The antimicrobial activity of ZnO was tested on bacteria using the agar well diffusion method to identify the samples that exhibited microbial inhibition. The results showed that no antibacterial activity was detected. The kinetic study of methyl orange adsorption on ZnO highlights several important aspects. Adsorption equilibrium is reached after 15 minutes, indicating fast kinetics. Approximately 40% of methyl orange is removed during this period, reflecting a moderate efficiency of the process. ZnO doped with 10% manganese shows the best performance, also achieving 40% removal, indicating that doping improves the material’s adsorption properties. Regarding photolysis and photocatalysis, the results showed that the removal rate of methyl orange by photolysis alone is very low, indicating a low efficiency of the process in the absence of a catalyst. On the other hand, photocatalysis shows rapid degradation, which can be observed from the first minutes of exposure to radiation. A removal rate of about 75% is achieved after 15 minutes. The most effective catalyst in this study is ZnO doped with 2% manganese, indicating a positive effect of activation on photocatalytic activity. The optimal conditions for the removal of methyl orange by the photocatalytic procedure are neutral pH, room temperature, a ZnO concentration of 1 g/L, and a methyl orange concentration of 10-4 mol/L.