Ultrasound-Assisted Dispersion of Metal Nanoparticles on Clay for Reduction of Organic Pollutants and Antimicrobial Activities

Water pollution by persistent dyes and bacteria has become one of the major environmental concerns. One of the most widely used strategies is the use of supported metal nanoparticles (MNPs) to remove a wide variety of dyes. This work concerns the dispersion of MNPs (M = Ag, Zn, and Cu) on kaolin clay using ultrasonic irradiation. The resulting solids were used as catalysts to reduce methylene blue (MB), methyl orange (MO), and orange G (OG) dyes in a simple and binary system. The obtained results showed that ultrasonic irradiation produced a good dispersion of MNPs with ultrafine sizes. According to XPS and TEM analysis, the MNPs (M = Ag, Cu, and Zn) were well formed. Catalytic tests showed that AgNPs-modified kaolin (K-Ag) was the most efficient compared with other catalysts modified by ZnNPs and CuNPs. In all tests, the K-Ag catalyst was more efficient with MB dye than with azo dyes. It was shown that the reduction of dyes is influenced by the concentration of the starting reactants, the mass of the catalyst, and the nature of the dye used. The rate constants were calculated to be 83.10⁻⁴ and 24.10⁻⁴ s⁻¹ for MB and MO dyes, respectively. For the system containing a mixture of dyes, the K-Ag catalyst was more selective with MB dye. The reuse of the K-Ag catalyst showed good results without losing its performance. Antibacterial applications showed that K-Cu material was the most efficient overall bacteria.