Abstract
In this work, mesoporous silica MCM-41 was prepared by hydrothermal route, and the obtained as-synthesized material (CTA-MCM-41) was modified by two different methods using silver and cerium assisted by thermal treatment. The modified materials were characterized by XRD, FTIR, XRF, XPS, nitrogen sorption measurements at-196 degrees C, SEM, and TEM analyses. The modified materials were tested as catalysts in a simple and binary system via the reduction reaction of Methylene Blue (MB), Congo Red (CR), 4-Nitrophenol (4-NP), Methyl Or-ange (MO), Orange G (OG) in the presence of NaBH4. The effect of the nanoparticles size, their dispersions, the nature of the organic pollutant, the initial concentration of the organic pollutant, and the concentration of the reducing agent NaBH4 have been studied and discussed. The obtained results confirmed that the preparation method plays an important role in the content and nature of nanoparticles, their sizes, their dispersions, and also on their catalytic performance. The Ag-Ce-MCM-2 material was selected as the best catalyst due to the synergistic effect between AgNPs and CeO2. The rate constant calculated in the simple system for the different pollutants was as follows: 0.1829 s-1, 0.1762 s-1, 0.0606 s-1, 0.0585 s-1, 0.0556 s-1 for MO, OG, MB, 4-NP, CR, respectively. The reduction in a binary system containing CR and MB or MO and MB was in competition, in which the CR or MO degrades together with the MB dye. Whereas for the other binary systems containing 4-NP/ MB or OG/MB, the catalyst Ag-Ce-MCM-2 was more selective towards the MB dye. This catalyst demonstrated efficiency and reusability across different cycles, in which the conversion of the MB dye was complete in each reuse.