Natural zeolites, clinoptilolite from the Golobradovo deposit, Bulgaria, and mordenite from the Lyaskovets deposit in Eastern Rhodopes, Bulgaria, were used for the preparation of natural-zeolite-supported CeО₂@Polybenzimidazole (PBI) hybrid materials with green-synthesized ceria incorporated using Veronica officinalis L. plant extract. In order to prepare hybrid composite powders of the natural zeolites/green-synthesized CeО₂, the surface was impregnated with the use of ethanolic KOH solution of meta-polybenzimidazole as dispersant media. The chemical and phase composition, structure, and thermal behavior of the obtained composite materials were investigated through X-ray fluorescence analyses, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The presence of CeO₂ (33.1 mass % and 32 mass %) in the prepared clinoptilolite- or mordenite-supported green-synthesized CeО₂@Polybenzimidazole was determined using X-ray fluorescence analysis. The photocatalytic properties of the synthesized hybrid materials were tested in the reaction of oxidative photocatalytic degradation of 5 ppm Reactive Black 5 (RB5) dye as a model pollutant under UV light irradiation. The photocatalytic results show that the RB5 dye demonstrates a higher degree of degradation (98%) with 120 minutes of UV irradiation in the presence of mordenite-supported/CeO₂@PBI as the photocatalyst compared to that with the clinoptilolite-supported/CeO₂@PBI (14%).

Acknowledgments: The authors express their gratitude to the project with the Bulgarian National Science Fund, KP-06-N69/8 (КП-06-Н69/8), “Novel polymer-hybrid materials containing (bio)synthesized metal oxide particles with improved photocatalytic and antimicrobial potential”, for the financial support. The authors acknowledge the technical support from the project PERIMED BG05M2OP001-1.002-0005 /29.03.2018 (2018–2023). Thanks to Liliya Tsvetanova for her technical assistance in the XRF analysis.