Disposal of copper, manganese and iron is particularly problematic in wastewater of metallurgical... more Disposal of copper, manganese and iron is particularly problematic in wastewater of metallurgical and galvanization plants, the electronics industry and agriculture. On the other hand, volatile organic compounds (VOCs), emitted from industrial processes, transportation and consumer products are the main class of air pollutants. The study revealed the potential of waste metal-loaded zeolite, generated through wastewater treatment procedures, to be utilised as an effective VOC removal catalyst for air treatment. In the first step, we have evaluated the sorption performance of natural zeolite clinoptilolite (HEU type), and synthetic zeolite 4A (LTA type) for the simultaneous removal of Cu2+, Mn2+ and Fe3+ species from aqueous solution. By a detailed sorption study, we determined the optimum sorption conditions and maximum metal concentrations in wastewater that can be after treatment disposed of in rivers or municipal plants. The efficiency of both zeolites for metal immobilization was demonstrated for concentrations up to 5 mg metals/1 g zeolite. These waste Cu-, Mn- and Fe-loaded zeolites were thermally treated at 540 °C before the second step, where we evaluated their catalytic performance in removing VOC. The thermally treated waste Cu-, Mn- and Fe-loaded natural zeolite clinoptilolite showed good catalytic performance in total toluene oxidation as a model VOC (conversion rate up to 96% at 510°C) and cycling stability (less than 15% drop in conversion rate in 4 h). In contrast, this is not the case for thermally treated waste Cu-, Mn- and Fe-loaded synthetic zeolite 4A.
The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst Ti... more The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst TiO 2 is usually attributed to influences of the physicochemical properties of the catalyst, pollutant type, pH, temperature, O 3 concentration, and other factors. It is also often claimed that good adsorption on the TiO 2 surface is beneficial for the occurrence of synergism. Herein, we tested these assumptions by using five different commercial TiO 2 photocatalysts (P25, PC500, PC100, PC10 and JRC-TiO-6) in three advanced oxidation systems-photocatalysis (O 2 /TiO 2 /UV), catalytic ozonation (O 3 /TiO 2) and PH-OZ (O 3 /TiO 2 /UV)-for the degradation of two pollutants (dichloroacetic acid-DCAA and thiacloprid) simultaneously present in water. The synergistic effect in PH-OZ was much more pronounced in the case of thiacloprid, a molecule with low adsorption on the surface of the catalyst-in contrast to DCAA with stronger adsorption. The faster kinetics of catalytic ozonation (O 3 /TiO 2) correlated with the higher exposed surface area of TiO 2 agglomerates, independent of the (lower) BET surfaces of the primary particles. Nevertheless, DCAA mineralization on the TiO 2 surface was much faster than thiacloprid degradation in solution. Therefore, we propose that a high BET surface area of the photocatalyst is crucial for fast surface reactions (DCAA mineralization), while good dispersion-the high exposed surface area of the (small) agglomerates-and charge separation play an important role in photocatalytic degradation or PH-OZ of less adsorbed organic pollutants (thiacloprid).
Hematite (α-Fe 2 O 3) is one of the most studied materials for electrochemical water splitting an... more Hematite (α-Fe 2 O 3) is one of the most studied materials for electrochemical water splitting and photovoltaic applications. A plethora of experimental techniques have been applied in order to unveil the mechanisms of charge migration in hematite and to understand the kinetics of the multistep processes responsible for its performance. The common concept is based on the formation of small electron polarons within a few picoseconds, having a lifetime of up to a few nanoseconds. In this work, stepscan transient IR spectroscopy was used to follow IR spectral changes in the semiconductor following pulsed UV excitation. The transient spectrum resembled the spectrum of maghemite, suggesting a similar local distortion following excitation. The most pronounced change was the appearance of an absorption peak at 640 cm −1 , whose intensity was the highest at 40−50 ns after excitation, and its lifetime was found to be in the order of a few hundreds of nanoseconds that is considerably longer than what is usually considered as carriers' lifetime in hematite. The intensity of the 640 cm −1 peak was found to change with the film thickness in a manner that correlated with the photoinduced current measured by linear sweep voltammetry. This correlation demonstrates that transient IR spectroscopy in the nanosecond range may be useful as a tool for studying photoinduced phenomena in photoactive materials.
Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, produc... more Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, producing more than a thousand research papers per year over the past decade. In this review, immobilized photocatalysts operating under sunlight are highlighted. First, a literature review of solar-driven films is presented, along with some fundamental operational differences in relation to reactions involving suspended nanoparticles. Common strategies for achieving sunlight activity from films are then described, including doping, surface grafting, semiconductor coupling, and defect engineering. Synthetic routes to fabricate photocatalytically active films are briefly reviewed, followed by the important factors that determine solar photocatalysis efficiency, such as film thickness and structure. Finally, some important and specific characterization methods for films are described. This review shows that there are two main challenges in the study of photocatalytic materials in the form of (thin) films. First, the production of stable and efficient solar-driven films is still a challenge that requires an integrated approach from synthesis to characterization. The second is the difficulty in properly characterizing films. In any case, the research community needs to address these, as solar-driven photocatalytic films represent a viable option for sustainable air and water purification.
Synthesis of zinc oxide (ZnO) nanoparticles (NPs) was mediated by plant extracts to assist in the... more Synthesis of zinc oxide (ZnO) nanoparticles (NPs) was mediated by plant extracts to assist in the reduction of zinc atoms during the synthesis and act as a capping agent during annealing. The preparation used ethanolic extracts from the roots of Japanese knotweed (Fallopia japonica). Two major outcomes could be made. (i) A synergistic effect of multiple polyphenolic components in the extract is needed to achieve the capping effect of crystallite growth during thermal annealing at 450°C characterized by an exponential growth factor (n) of 4.4 compared to n = 3 for bare ZnO. (ii) Synergism between the ZnO NPs and plant extracts resulted in superior antimicrobial activity against both Gram-positive bacteria, e.g., Staphylococcus aureus, and Gram-negative bacteria, e.g., Escherichia coli and Campylobacter jejuni. The materials were also tested for their antimicrobial activity against S. aureus under ultraviolet (UV) illumination. Also here, the photocatalyst prepared with plant extracts was found to be superior. The residues of the plant extract molecules on the surface of the catalyst were identified as the main cause of the observed differences, as proved by thermal gravimetry. Such a preparation using ethanolic extract of Fallopia japonica could serve as a more controlled synthesis of ZnO and potentially other metal oxides, with low environmental impact and high abundance in nature.
Journal of Photochemistry and Photobiology A: Chemistry, 2017
Photocatalytic properties of titanium dioxide have been exploited for various purposes, including... more Photocatalytic properties of titanium dioxide have been exploited for various purposes, including the photocatalytic purification of air, where an immobilized catalyst is preferred over a dispersed one as it has much higher application value. In this work, we have investigated the photocatalytic degradation of toluene on titania nanoparticles immobilized on fiberglass cloth. The progress of the reaction was monitored using a self-constructed photoreactor equipped with UVA lamps. Commercially available P25 and PC500 powder catalysts were successfully immobilized on fiberglass cloth by a “sol suspension” procedure. The prepared photocatalysts were characterized by scanning electron microscopy (SEM), UV–vis-NIR diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The highest photocatalytic degradation performance was obtained for the PC500 catalyst followed by a 1:1 mixture of P25 and PC500 and the lowest performance was observed in case of the P25 immobilized catalyst. The highest degradation rate of PC500 can be ascribed to its smallest particle size and highest surface area in comparison to others.
Ni and Zn show a winning combination of redox potential and band positions of TiO2 supported meta... more Ni and Zn show a winning combination of redox potential and band positions of TiO2 supported metal-oxo-nanoclusters for enhanced solar-light activity. However, Ni is the only metal which has a positive effect on solar photoactivity in both oxidation and reduction reactions.
The study is aimed at evaluating the potential of immobilized TiO 2-based zeolite composite for s... more The study is aimed at evaluating the potential of immobilized TiO 2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO 2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO 2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO 2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO 2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflec-tance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO 2-FeZ in comparison to pure TiO 2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/ TiO 2-FeZ/H 2 O 2 process was investigated. TiO 2-FeZ demonstrated higher photocatalytic activity than pure TiO 2 under solar irradiation in acidic conditions and presence of H 2 O 2 .
Different types of TiO2 –SiO2 composites in the form of powder or films have been reported as eff... more Different types of TiO2 –SiO2 composites in the form of powder or films have been reported as efficient photocatalysts for decomposition of organic compounds in liquid and gas phase. Herein, we report for the first time on the formation of efficient TiO2 –SiO2 films made from acidic organic-free colloidal solution of TiO 2 anatase nanoparticles (AS) and mesoporous SiO2 (SBA-15) with 100% loading (TiO2 : SiO2 molar ratio 1:1) under simple and low cost procedure. AS was prepared from metatitanic acid precursor using a novel, environmentally friendly approach of TiO2 nanoparticles precipitation with NaOH and peptiza-tion with HCl. These AS/SBA-15 films, immobilized by brush deposition on glass carriers, showed total decomposition of toluene and 91% decomposition of formaldehyde as model VOCs in gas phase, at room temperature under UVA irradiation in lab-made batch photoreactor. The trend of photocatalytic efficiency for decomposition of formaldehyde was AS/SBA-15 > P25 > PC500 > AS. The adsorption capability of the AS/SBA-15 was higher in comparison to its pure TiO2 analogues (AS, P25, PC500) in case of toluene. Turnover frequency (TOF) of the AS/SBA-15 was approximately six times higher in comparison to its pure TiO2 analogue AS for toluene and formaldehyde. The potential of AS/SBA-15 for the use in air cleaning devices is finally discussed.
IOP Conference Series: Materials Science and Engineering, 2012
When photocatalytic water treatment is concerned, suspended catalyst in the aqueous phase is usua... more When photocatalytic water treatment is concerned, suspended catalyst in the aqueous phase is usually more efficient than immobilized on an inert support, but in the former case an undesirable separation/recycling step is needed. We have therefore concentrated on the preparation of immobilized catalysts in the form of films on glass and aluminium supports. The low-temperature sol-gel processing route to obtain transparent thin TiO 2 /SiO 2 films for selfcleaning purposes and thicker TiO 2 /SiO 2 coatings for efficient removal of pollutants in water and air are presented. The synthesis is based on a production of a nanocrystalline titania sol with a silica binder that after deposition does not require thermal treatment at high temperatures. Depending on the target application, some specific synthesis parameters and photocatalytic activity testing conditions are illustrated. For water-cleaning coatings fast kinetics is required, which was achieved by addition of a highly active titania powder into the sol. The same preparation procedure was used to prepare efficient air-cleaning coatings. On the other hand, self-cleaning films were thinner and transparent to keep the original appearance of the substrate and they solidified at ambient conditions. Advanced methodologies to evaluate photocatalytic activity of the films were applied.
For air-cleaning, TiO2 photocatalysis represents one of the very efficient advanced oxidation pro... more For air-cleaning, TiO2 photocatalysis represents one of the very efficient advanced oxidation processes (AOPs) that can decompose chemically and microbiologically stable volatile organic compounds (VOCs). However, the photocatalytic activity of nanocrystalline TiO2 powders can be significantly suppressed due to TiO2's poor adsorption characteristics for organic compounds and its relatively low surface area. The present study sought to solve this problem by immobilising nanocrystalline TiO2 in the porous silicate substrate. Two titania sources were used in an aqueous solution form: a suspension from a TiO2 producer in Slovenia, Cinkarna Celje (CC-40) and a TiO2 sol, prepared by a low-temperature synthesis developed at the University of Nova Gorica (TiO2-UNG). Two different types of mesoporous silica were used: SBA-15 with an ordered hexagonal pore arrangement and KIL-2 with disordered inter-particle mesoporosity. The structural characteristics, adsorption properties and photocatalytic activity of catalysts deposited on aluminium plates as thin films were investigated. CC-40 exhibited higher adsorption and photocatalytic activity than TiO2-UNG due to the greater quantity of Ti-OH groups on its surface. The addition of mesoporous silica led to higher adsorption and catalytic activity for both TiO2 sources. SBA-15 was more efficient than KIL-2.
Disposal of copper, manganese and iron is particularly problematic in wastewater of metallurgical... more Disposal of copper, manganese and iron is particularly problematic in wastewater of metallurgical and galvanization plants, the electronics industry and agriculture. On the other hand, volatile organic compounds (VOCs), emitted from industrial processes, transportation and consumer products are the main class of air pollutants. The study revealed the potential of waste metal-loaded zeolite, generated through wastewater treatment procedures, to be utilised as an effective VOC removal catalyst for air treatment. In the first step, we have evaluated the sorption performance of natural zeolite clinoptilolite (HEU type), and synthetic zeolite 4A (LTA type) for the simultaneous removal of Cu2+, Mn2+ and Fe3+ species from aqueous solution. By a detailed sorption study, we determined the optimum sorption conditions and maximum metal concentrations in wastewater that can be after treatment disposed of in rivers or municipal plants. The efficiency of both zeolites for metal immobilization was demonstrated for concentrations up to 5 mg metals/1 g zeolite. These waste Cu-, Mn- and Fe-loaded zeolites were thermally treated at 540 °C before the second step, where we evaluated their catalytic performance in removing VOC. The thermally treated waste Cu-, Mn- and Fe-loaded natural zeolite clinoptilolite showed good catalytic performance in total toluene oxidation as a model VOC (conversion rate up to 96% at 510°C) and cycling stability (less than 15% drop in conversion rate in 4 h). In contrast, this is not the case for thermally treated waste Cu-, Mn- and Fe-loaded synthetic zeolite 4A.
The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst Ti... more The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst TiO 2 is usually attributed to influences of the physicochemical properties of the catalyst, pollutant type, pH, temperature, O 3 concentration, and other factors. It is also often claimed that good adsorption on the TiO 2 surface is beneficial for the occurrence of synergism. Herein, we tested these assumptions by using five different commercial TiO 2 photocatalysts (P25, PC500, PC100, PC10 and JRC-TiO-6) in three advanced oxidation systems-photocatalysis (O 2 /TiO 2 /UV), catalytic ozonation (O 3 /TiO 2) and PH-OZ (O 3 /TiO 2 /UV)-for the degradation of two pollutants (dichloroacetic acid-DCAA and thiacloprid) simultaneously present in water. The synergistic effect in PH-OZ was much more pronounced in the case of thiacloprid, a molecule with low adsorption on the surface of the catalyst-in contrast to DCAA with stronger adsorption. The faster kinetics of catalytic ozonation (O 3 /TiO 2) correlated with the higher exposed surface area of TiO 2 agglomerates, independent of the (lower) BET surfaces of the primary particles. Nevertheless, DCAA mineralization on the TiO 2 surface was much faster than thiacloprid degradation in solution. Therefore, we propose that a high BET surface area of the photocatalyst is crucial for fast surface reactions (DCAA mineralization), while good dispersion-the high exposed surface area of the (small) agglomerates-and charge separation play an important role in photocatalytic degradation or PH-OZ of less adsorbed organic pollutants (thiacloprid).
Hematite (α-Fe 2 O 3) is one of the most studied materials for electrochemical water splitting an... more Hematite (α-Fe 2 O 3) is one of the most studied materials for electrochemical water splitting and photovoltaic applications. A plethora of experimental techniques have been applied in order to unveil the mechanisms of charge migration in hematite and to understand the kinetics of the multistep processes responsible for its performance. The common concept is based on the formation of small electron polarons within a few picoseconds, having a lifetime of up to a few nanoseconds. In this work, stepscan transient IR spectroscopy was used to follow IR spectral changes in the semiconductor following pulsed UV excitation. The transient spectrum resembled the spectrum of maghemite, suggesting a similar local distortion following excitation. The most pronounced change was the appearance of an absorption peak at 640 cm −1 , whose intensity was the highest at 40−50 ns after excitation, and its lifetime was found to be in the order of a few hundreds of nanoseconds that is considerably longer than what is usually considered as carriers' lifetime in hematite. The intensity of the 640 cm −1 peak was found to change with the film thickness in a manner that correlated with the photoinduced current measured by linear sweep voltammetry. This correlation demonstrates that transient IR spectroscopy in the nanosecond range may be useful as a tool for studying photoinduced phenomena in photoactive materials.
Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, produc... more Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, producing more than a thousand research papers per year over the past decade. In this review, immobilized photocatalysts operating under sunlight are highlighted. First, a literature review of solar-driven films is presented, along with some fundamental operational differences in relation to reactions involving suspended nanoparticles. Common strategies for achieving sunlight activity from films are then described, including doping, surface grafting, semiconductor coupling, and defect engineering. Synthetic routes to fabricate photocatalytically active films are briefly reviewed, followed by the important factors that determine solar photocatalysis efficiency, such as film thickness and structure. Finally, some important and specific characterization methods for films are described. This review shows that there are two main challenges in the study of photocatalytic materials in the form of (thin) films. First, the production of stable and efficient solar-driven films is still a challenge that requires an integrated approach from synthesis to characterization. The second is the difficulty in properly characterizing films. In any case, the research community needs to address these, as solar-driven photocatalytic films represent a viable option for sustainable air and water purification.
Synthesis of zinc oxide (ZnO) nanoparticles (NPs) was mediated by plant extracts to assist in the... more Synthesis of zinc oxide (ZnO) nanoparticles (NPs) was mediated by plant extracts to assist in the reduction of zinc atoms during the synthesis and act as a capping agent during annealing. The preparation used ethanolic extracts from the roots of Japanese knotweed (Fallopia japonica). Two major outcomes could be made. (i) A synergistic effect of multiple polyphenolic components in the extract is needed to achieve the capping effect of crystallite growth during thermal annealing at 450°C characterized by an exponential growth factor (n) of 4.4 compared to n = 3 for bare ZnO. (ii) Synergism between the ZnO NPs and plant extracts resulted in superior antimicrobial activity against both Gram-positive bacteria, e.g., Staphylococcus aureus, and Gram-negative bacteria, e.g., Escherichia coli and Campylobacter jejuni. The materials were also tested for their antimicrobial activity against S. aureus under ultraviolet (UV) illumination. Also here, the photocatalyst prepared with plant extracts was found to be superior. The residues of the plant extract molecules on the surface of the catalyst were identified as the main cause of the observed differences, as proved by thermal gravimetry. Such a preparation using ethanolic extract of Fallopia japonica could serve as a more controlled synthesis of ZnO and potentially other metal oxides, with low environmental impact and high abundance in nature.
Journal of Photochemistry and Photobiology A: Chemistry, 2017
Photocatalytic properties of titanium dioxide have been exploited for various purposes, including... more Photocatalytic properties of titanium dioxide have been exploited for various purposes, including the photocatalytic purification of air, where an immobilized catalyst is preferred over a dispersed one as it has much higher application value. In this work, we have investigated the photocatalytic degradation of toluene on titania nanoparticles immobilized on fiberglass cloth. The progress of the reaction was monitored using a self-constructed photoreactor equipped with UVA lamps. Commercially available P25 and PC500 powder catalysts were successfully immobilized on fiberglass cloth by a “sol suspension” procedure. The prepared photocatalysts were characterized by scanning electron microscopy (SEM), UV–vis-NIR diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The highest photocatalytic degradation performance was obtained for the PC500 catalyst followed by a 1:1 mixture of P25 and PC500 and the lowest performance was observed in case of the P25 immobilized catalyst. The highest degradation rate of PC500 can be ascribed to its smallest particle size and highest surface area in comparison to others.
Ni and Zn show a winning combination of redox potential and band positions of TiO2 supported meta... more Ni and Zn show a winning combination of redox potential and band positions of TiO2 supported metal-oxo-nanoclusters for enhanced solar-light activity. However, Ni is the only metal which has a positive effect on solar photoactivity in both oxidation and reduction reactions.
The study is aimed at evaluating the potential of immobilized TiO 2-based zeolite composite for s... more The study is aimed at evaluating the potential of immobilized TiO 2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO 2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO 2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO 2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO 2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflec-tance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO 2-FeZ in comparison to pure TiO 2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/ TiO 2-FeZ/H 2 O 2 process was investigated. TiO 2-FeZ demonstrated higher photocatalytic activity than pure TiO 2 under solar irradiation in acidic conditions and presence of H 2 O 2 .
Different types of TiO2 –SiO2 composites in the form of powder or films have been reported as eff... more Different types of TiO2 –SiO2 composites in the form of powder or films have been reported as efficient photocatalysts for decomposition of organic compounds in liquid and gas phase. Herein, we report for the first time on the formation of efficient TiO2 –SiO2 films made from acidic organic-free colloidal solution of TiO 2 anatase nanoparticles (AS) and mesoporous SiO2 (SBA-15) with 100% loading (TiO2 : SiO2 molar ratio 1:1) under simple and low cost procedure. AS was prepared from metatitanic acid precursor using a novel, environmentally friendly approach of TiO2 nanoparticles precipitation with NaOH and peptiza-tion with HCl. These AS/SBA-15 films, immobilized by brush deposition on glass carriers, showed total decomposition of toluene and 91% decomposition of formaldehyde as model VOCs in gas phase, at room temperature under UVA irradiation in lab-made batch photoreactor. The trend of photocatalytic efficiency for decomposition of formaldehyde was AS/SBA-15 > P25 > PC500 > AS. The adsorption capability of the AS/SBA-15 was higher in comparison to its pure TiO2 analogues (AS, P25, PC500) in case of toluene. Turnover frequency (TOF) of the AS/SBA-15 was approximately six times higher in comparison to its pure TiO2 analogue AS for toluene and formaldehyde. The potential of AS/SBA-15 for the use in air cleaning devices is finally discussed.
IOP Conference Series: Materials Science and Engineering, 2012
When photocatalytic water treatment is concerned, suspended catalyst in the aqueous phase is usua... more When photocatalytic water treatment is concerned, suspended catalyst in the aqueous phase is usually more efficient than immobilized on an inert support, but in the former case an undesirable separation/recycling step is needed. We have therefore concentrated on the preparation of immobilized catalysts in the form of films on glass and aluminium supports. The low-temperature sol-gel processing route to obtain transparent thin TiO 2 /SiO 2 films for selfcleaning purposes and thicker TiO 2 /SiO 2 coatings for efficient removal of pollutants in water and air are presented. The synthesis is based on a production of a nanocrystalline titania sol with a silica binder that after deposition does not require thermal treatment at high temperatures. Depending on the target application, some specific synthesis parameters and photocatalytic activity testing conditions are illustrated. For water-cleaning coatings fast kinetics is required, which was achieved by addition of a highly active titania powder into the sol. The same preparation procedure was used to prepare efficient air-cleaning coatings. On the other hand, self-cleaning films were thinner and transparent to keep the original appearance of the substrate and they solidified at ambient conditions. Advanced methodologies to evaluate photocatalytic activity of the films were applied.
For air-cleaning, TiO2 photocatalysis represents one of the very efficient advanced oxidation pro... more For air-cleaning, TiO2 photocatalysis represents one of the very efficient advanced oxidation processes (AOPs) that can decompose chemically and microbiologically stable volatile organic compounds (VOCs). However, the photocatalytic activity of nanocrystalline TiO2 powders can be significantly suppressed due to TiO2's poor adsorption characteristics for organic compounds and its relatively low surface area. The present study sought to solve this problem by immobilising nanocrystalline TiO2 in the porous silicate substrate. Two titania sources were used in an aqueous solution form: a suspension from a TiO2 producer in Slovenia, Cinkarna Celje (CC-40) and a TiO2 sol, prepared by a low-temperature synthesis developed at the University of Nova Gorica (TiO2-UNG). Two different types of mesoporous silica were used: SBA-15 with an ordered hexagonal pore arrangement and KIL-2 with disordered inter-particle mesoporosity. The structural characteristics, adsorption properties and photocatalytic activity of catalysts deposited on aluminium plates as thin films were investigated. CC-40 exhibited higher adsorption and photocatalytic activity than TiO2-UNG due to the greater quantity of Ti-OH groups on its surface. The addition of mesoporous silica led to higher adsorption and catalytic activity for both TiO2 sources. SBA-15 was more efficient than KIL-2.
Uploads
Papers by Andraž Šuligoj