Content description of the project
The objective of the EU Zero Pollution Action Plan for air, water, and soil is to create an environment free of toxic substances. As pollution levels are increasing dramatically each year, achieving the zero-pollution vision by 2030 requires immediate action. Photocatalysis represents a promising solution for wastewater treatment. During photocatalysis, electron–hole pairs are generated, which participate in photooxidation and photoreduction reactions, leading to the complete mineralization of (organic) pollutants under light irradiation (UV or visible).
The project envisaged the preparation of new photocatalysts at the Laboratory of Applied Nanomaterials at the University of Miskolc, Hungary. This was followed by the development of hybrid Z-scheme semiconductors based on (Fe/Ca)-titanates combined with bismuth-based materials and carbon nanotubes. These materials are expected to be effective in removing organic pollutants from industrial wastewater. The composites were used for the degradation of pollutants (dyes and pharmaceutical compounds) in laboratory experiments at the Faculty of Chemistry and Chemical Technology, University of Ljubljana, and the most efficient materials were further applied at the industrial level using real wastewater streams. The efficiency of the composites was evaluated alongside the development of an advanced reactor system implemented within a bilateral Slovenian–Hungarian research project.
This work was carried out in international collaboration with Prof. Blaž Likozar (National Institute of Chemistry), who has extensive complementary expertise in photocatalytic reactors of various scales (laboratory and pilot) for water treatment. The Hungarian group has more than 10 years of experience in photocatalysis and materials design.
Project phases and their implementation
The project focused on the development of advanced semiconductor materials for efficient wastewater treatment and on the design and fabrication of integrated photocatalytic reactor systems for their application. The research was conducted in close collaboration between the Slovenian and Hungarian teams and included material synthesis, characterization, process modeling, and testing under realistic conditions.
In the first phase, novel composite materials based on titanates, basic bismuth nitrate (BBN), and carbon nanotubes (CNTs) were synthesized using different approaches. Special emphasis was placed on preparing BBN composites with various forms of titanium dioxide as well as with the mineral ilmenite (FeTiO₃), using hydrothermal methods to ensure direct contact between components, which is crucial for efficient photocatalytic performance.
Subsequently, synthesis conditions were optimized to improve interfacial compatibility and material stability. Ilmenite was acid-pretreated to remove surface impurities and activate reactive sites. Due to its lower specific surface area compared to TiO₂, the mass ratios of components were adjusted to achieve better surface coverage and enhanced composite efficiency. Photochemical and chemical stability of the prepared materials was also investigated.
A key part of the project involved computational modeling of photocatalytic processes at the atomic level using density functional theory (DFT and TD-DFT) combined with microkinetic models. The results demonstrated that excited states significantly reduce reaction energy barriers on catalyst surfaces and that catalytic activity strongly depends on electronic structure. Additionally, hybrid systems based on graphitic carbon nitride were studied, showing potential for efficient storage of light energy in chemical products.
The synthesized materials were thoroughly characterized using advanced physicochemical techniques (XRD, SEM, TEM, XPS, nitrogen adsorption, FTIR), providing insight into their crystal structure, morphology, and surface properties. It was found that BBN successfully attaches to commercial TiO₂ (P25), whereas attachment to ilmenite was less effective, highlighting the importance of surface chemistry and phase boundaries in composite formation.
The developed materials were tested for the treatment of both real and model wastewater obtained from industrial partners. Very promising results were achieved, although detailed data remain confidential. Photocatalytic efficiency was evaluated using model pollutants such as the pharmaceutical compound ibuprofen. The TiO₂–BBN composite showed outstanding activity, achieving complete degradation of ibuprofen in a very short time under both UV and visible light, representing a significant improvement over standard P25.
To facilitate practical application, advanced photocatalytic reactors were developed, including a continuous tubular reactor and a batch reactor equipped with UV LED illumination. Particular attention was given to immobilizing catalysts on supports (e.g., glass beads), reducing nanoparticle loss and enabling more stable operation. Light distribution and mass transfer within the reactors were also optimized, significantly influencing process efficiency.
Overall, the project represents a comprehensive approach that integrates the synthesis of novel materials, fundamental understanding, reactor engineering, and application testing in real environments, with the clear goal of developing efficient and sustainable wastewater treatment technologies.
Composition of the project team with links to SICRIS
At the National Institute of Chemistry the project group Dr. Blaž Likozar (https://cris.cobiss.net/ecris/si/sl/researcher/18823)
Dr. Nataša Novak Tušar (https://cris.cobiss.net/ecris/si/sl/researcher/8049)
Dr. Matej Huš (https://cris.cobiss.net/ecris/si/sl/researcher/38950)
Dr. Andraž Pavlišič (https://cris.cobiss.net/ecris/si/sl/researcher/39143)
Matic Grom (https://cris.cobiss.net/ecris/si/sl/researcher/32589)
Dr. Andraž Šuligoj (https://cris.cobiss.net/ecris/si/sl/researcher/39161)
Dr. Urška Lavrenčič Štangar (https://cris.cobiss.net/ecris/si/sl/researcher/7521)
Dr. Romana Cerc Korošec (https://cris.cobiss.net/ecris/si/sl/researcher/9333)
Dr. Boštjan Žener (https://cris.cobiss.net/ecris/si/sl/researcher/44068)
Bibliographic references arising directly from the project
[1] KOVAČIČ, Žan et al. Ab initio modelling of photocatalytic CO2 reduction reactions over Cu/TiO2 semiconductors including the electronic excitation effects. Chemical engineering journal. 2024, vol. 485, 149894, str. 1-13 [COBISS.SI-ID 188821763]
[2] ZOLTOWSKA, Sonia et al. Merging heterogeneous graphitic carbon nitride photocatalysis with cobaloxime catalysis in uphill dehydrogenative synthesis of anilines. ChemSusChem. 2025, vol. 18, iss. 12, e202402439, str. 1-10, [COBISS.SI-ID 231489795]
[3] DAS, Susmita, et al. Artificial neural network modeling of photocatalytic degradation of pollutants : a review of photocatalyst, optimum parameters and model topology. Catalysis reviews: science and engineering. 2025, vol. 67, iss. 3, str. 544-578, [COBISS.SI-ID 192168707]
[4] JAMIL, Qasim, ŽENER, Boštjan, PUTAR, Ula, MATOH, Lev. Continuous flow photocatalytic reactor for degradation of selected pollutants : modeling, kinetics, mineralization rate, and toxicity assessment. Heliyon. 2024, vol. 10, iss. 21, e40019, str. 1-14, [COBISS.SI-ID 214006531]
[5] JAMIL, Qasim, RANA, Khush Bakhat, MATOH, Lev. A CFD study on optimization of mass transfer and light distribution in a photocatalytic reactor with immobilized photocatalyst on spheres. Water. 2024, vol. 16, iss. 13, 1828, str. 1-13, [COBISS.SI-ID 199998211]
[6] ŠULIGOJ, Andraž, et al. Transparent vanadium doped titania-silica films : structural characterization and self-cleaning properties. Journal of environmental chemical engineering. 2024, vol. 12, issue 5, 113904, str. 1-14, [COBISS.SI-ID 206731267]
[7] ŠULIGOJ, Andraž et al. Enhanced Removal of Bisphenols Using Immobilized TiO2 in Photocatalytically Assisted Hydrodynamic Cavitation (accepted for publication in Ultrasonics Sonochemistry)
[8] ŽENER, Boštjan et al. Photocatalytic degradation of PFOA: Defluorination, toxicity assessment and catalyst regeneration (under review at Journal of Hazardous Materials Advances)
