Optical and EPR Spectroscopy of Microwave-Modified Natural Zeolite Activated with Zinc Oxide and Silver

Samples of natural zeolite from the Nor-Kokhb deposit (Armenia), activated with zinc oxide (30% ZnO) and silver (30% ZnO + 5% Ag), were studied during chemical and thermal treatment by microwave and traditional methods. It was previously shown that microwave processing is 3 times faster than the traditional method. The X-ray diffraction analysis shows the presence of zeolite in the form of clinoptilolite and zinc oxide in the studied samples. Based on the results of optical and EPR spectroscopy, the presence of Fe³⁺ ions in the framework and extra-framework positions of the zeolite of the studied samples was revealed. The study of diffuse reflectance spectra showed that in zeolite, which is a wide-gap material (with a band gap of 4.14 eV), the activation of 30% ZnO decreases the band gap to 3.38 eV, and with additional activation with a silver (30% ZnO + 5% Ag) the bandgap decreases to 3.31 eV. The photocatalytic activity of natural zeolite activated with zinc oxide (30% ZnO) and silver (30% ZnO + 5% Ag) was studied according to the decomposition reaction of methylene blue under UV irradiation.