The natural zeolites were ultrasonically treated and impregnated with silver nanoparticles. The surface stabilized silver nanoparticles dispersion was obtained using an effective electrochemical reduction method. The phase and elemental composition, structure of the Ag-impregnated zeolites (clinoptilolite and mordenite) was studied by various methods such as powder X-ray diffraction, X-ray fluorescence analyses and Fourier-transform infrared spectroscopy. The Ag-impregnated clinoptilolite and mordenite natural zeolite materials with 1.20 wt %, 0.97 wt %, 0.83 wt % and 1.18 wt % silver content were established by XRF analysis. As initial materials were used three types clinoptilolite from Beli Plast, Most, Golobradovo (Kardzhali, Bulgaria) deposits and mordenite from Lyaskovets deposit in Eastern Rhodopes, Bulgaria. The catalytic ability of Ag-mordenite and Ag-clinoptilolites was investigated in the ecologically important reaction of ozone decomposition. The Ag-loaded mordenite demonstrates the higher conversion degree of ozone more than 40% in comparison with Ag-clinoptilolite materials at room temperature.

Environmental pollution from ozone and wastewaters containing dyes from various industries is an important problem for humanity. In this study, novel composite catalysts based on manganese carbonate ore from the Obrochishte deposit, Bulgaria, were used successfully in two environmentally relevant catalytic processes—the ozone decomposition and photocatalytic decolourization of Malachite Green (MG) dye under UV illumination. Manganese carbonate ore/NiO, manganese oxides, and silver-containing composites were synthesized via co-precipitation, followed by calcination at 500 °C or hydrothermal treatment at 160 °C, and then thermal treatment. The phase and elemental composition, structure, morphology, and textural characteristics of the obtained composites were investigated using powder X-ray diffraction analysis, wavelength-dispersive X-ray fluorescence, Fourier-transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption isotherms, and the BET method. The materials exhibit a mesoporous structure. The results established that the thermally treated MnCO₃ ore/NiO, manganese oxides, and Ag-containing composites demonstrate a higher catalytic efficiency for the removal of ozone (85%, 93%, and 99%) in comparison with hydrothermally treated analogues—79%, 66%, and 98%, respectively. The thermally treated manganese carbonate ore/silver-containing composite exhibits the highest photocatalytic ability (83% degree of decolourization of MG dye) compared to the other investigated catalysts.

FAU-type zeolite NaX was successfully prepared using hydrothermal synthesis at 90 °C for 6 h. The Mn- and Cu-ion-exchanged NaX zeolites were obtained. After the ion exchange, the zeolite powders were thermally treated at 300 °C. As well as Ag-ion-exchanged zeolite, NaX and zeolite were impregnated with two types of Ag nanoparticle dispersions: citrate surface-stabilized (Cit@Ag NPs) and polymer-stabilized (PVP@Ag) nanoparticles. Silver nanoparticles were synthesized using the electrochemical reduction method. The changes in the phase and chemical composition and structure of the obtained zeolite powders before and after ion exchange or impregnation were investigated by PXRD analysis, FTIR spectroscopy, and XRF analysis. The results show that Mn, Cu-exchanged NaX, and that impregnated with Ag demonstrated catalytic abilities towards ozone decomposition in comparison with pure zeolite (non-catalytic activity).

In the present study the new manganese carbonate ore/copper and cobalt oxide-based catalysts were prepared using co-precipitation followed by calcination at 500◦C or by hydrothermal synthesis at 160◦C and then thermal treatment. The phase composition, structure, morphology, specific surface area and textural characteristics of the obtained composites were characterized by several methods as PXRD analysis, FTIR spectroscopy, SEM, nitrogen adsorption-desorption isotherms, and measurement of specific surface area. The PXRD analysis determined the average crystallite size of 10nm for Co3O4 and MnCo2O4 and 13–23nm for CuO phases. The synthesized composites exhibit mesoporous structure. The highest specific surface area (135m2/g) was established for thermally treated MnCO3 ore/cobalt oxide in comparison with the other investigated samples. The prepared materials were tested in two reactions – ozone decomposition and photocatalytic discolouration of Malachite Green (MG) dye as model pollutant under UV light. The results reveal that the hydrothermally treated MnCO3 ore/cobalt and copper oxide demonstrate higher catalytic ability about removal of ozone (87% and 63%) in comparison with the composites prepared by co-precipitation and calcination – 86% and 54%, respectively. Best results for discolouration of MG dye were achieved with MnCO3 ore/cobalt oxide-based photocatalyst (76%).