RESUMEN
In this work, the mesoporous silica MCM-41 was prepared by a hydrothermal method and then modified using silver and copper. The obtained samples were used as antibacterial/antifungal agents and as catalysts for the reduction of the following dyes: Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO), and Orange G (OG). Several parameters affecting the reduction of dyes were investigated and discussed such as the catalyst nature, the initial concentration of the dye, the dye nature, the selectivity of the catalyst in a binary system as well as the catalyst reuse. The catalysts were characterized using XRD, nitrogen sorption measurements, XRF, FTIR, XPS, SEM/EDS, and TEM. XRD, XPS, and TEM analysis clearly showed that the calcination of copper- and silver-modified silica leads to the formation of well-dispersed CuO and AgNPs having sizes between 5 and 10 nm. As determined by XRF analysis, the content of silver nanoparticles was higher compared to CuO in all samples. It has been shown that the dye reduction is influenced by the size and the content of nanoparticles as well as by their dispersions. The catalytic activity was shown to be the highest for the Ag-Cu-MCM(0.05) catalyst with a rate constant of 0.114, 0.102, 0.093, and 0.056 s-1 for MO, MB, CR, and OG dyes in the single-dye system, respectively. In the binary system containing MB/OG or MB/MO, the catalyst Ag-Cu-MCM(0.05) was more selective toward the MB dye. The reuse of the catalyst for three consecutive cycles showed higher MB conversion in a single system with an increase in reaction time. For antifungal and antibacterial properties, the application of calcined and uncalcined materials toward six different strains showed good results, but uncalcined materials showed the best results due to the synergistic effect between CuO and unreduced species Ag+ which are considered responsible for the antibacterial and antifungal action.
Asunto(s)
Contaminantes Ambientales , Nanopartículas del Metal , Cobre , Antifúngicos , Plata/farmacología , Colorantes , Rojo Congo , Dióxido de Silicio , Antibacterianos/farmacologíaRESUMEN
The development of new catalysts from abundant raw materials, generating attractive photocatalytic activity, constitutes a real challenge in the context of sustainable development concerns. In this setting, a dolomite was treated at 800 °C (D800) and then chemically modified by Ca(NO3)2 (CaD800) using a simple procedure. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy (EDS), solid state UV spectroscopy, and used as catalysts of pentachlorophenol (PCP) degradation in aqueous solutions under UV light irradiation. The treatment of dolomite at 800 °C enabled a full decarbonation of CaMg(CO3)2, with formation of CaO, Ca(OH)2, and MgO. Additional CaO was generated after chemical treatment as revealed by EDS analysis; the Ca/Mg ratio increased from 1.29 (D800) to 1.44 for CaD800. This CaO in aqueous medium hydrates by giving Ca(OH)2. CaD800 was found to be the best photocatalyst with a PCP degradation rate of 95% after only 1 h of treatment, for a CaD800/D800 degradation rate constant ratio of 1.58. In this regard, we investigated the Fourier transform infrared spectra of CaD800, PCP, and CaD800 loaded with PCP after degradation. We thus evidenced the involvement of Ca(OH)2 in the PCP degradation process. Catalytic activity was discussed through the contribution of OH radicals and electrodonation.