The decomposition of acetaldehyde and ethylene was investigated in a fluidized bed reactor filled with cenospheres coated with TiO2 and Pt nanoparticles. The process was conducted under UV-LED irradiation at temperatures ranging from 60 to 150 degrees C. The effectiveness of the TiO2 coating and the uniformity of the Pt deposition on cenospheres surface were confirmed through SEM, EDX, XRFS, and UV-Vis analyses. XRD analysis revealed the presence of crystalline mullite, cristobalite/quartz, and magnetite phases, along with non-stoichiometric amorphous aluminosilicates. TiO2/Pt-coated cenospheres demonstrated high and stable thermo-photocatalytic performance. At a temperature of 150 degrees C, a flow rate of 560 ml/min, and relative humidity levels ranging from 0% to 75%, the conversion of acetaldehyde surpassed 95%, accompanied by complete mineralization. Conversely, ethylene conversion exhibited a decline, from 89% to 67%, as the humidity level increased. At 60 degrees C, acetaldehyde conversion decreased to 71% under suboptimal conditions, whereas ethylene conversion was reduced to 24% in the absence of Pt and in humid gas. The increase in gas flow rate from 560 to 1200 ml/min (150 degrees C, dry conditions) led to a decline in acetaldehyde conversion from 99% to 93% and ethylene conversion from 89% to 77%. In summary, TiO2/Pt-coated cenospheres facilitate the efficient removal of acetaldehyde and ethylene through a multifaceted process that incorporates TiO2 photocatalysis, Pt-assisted thermal oxidation, and auxiliary photo-Fenton reactions associated with magnetite. This process is further enhanced by the hydrophilic nature of the cenospheres.

Polystyrene spheres with a size of 1 mm were coated by TiO2 (titanium dioxide) powder by two methods: wet impregnation from the titania slurry solution, followed by sintering at 140 degrees C, and dry sintering of mixed expanded polystyrene spheres with TiO2 powder at 140 degrees C. Such obtained materials were applied as the fluidized beds in the continuous flow photocatalytic reactor for removal of VOCs (Volatile Organic Compounds), such as acetaldehyde and ethylene from air. Materials were characterized by SEM/EDS, optical microscope, TG and UV-Vis/DR techniques. Concentration of the outlet gas was monitored by using Gas Chromatography and mineralization degree by the CO2 sensor. High initial concentrations of VOCs were used (439.7 mg/m3) for acetaldehyde and (246.4 mg/m3) for ethylene. The effect of 15 and 30 % bed fill and various gas flow rates were investigated. The photocatalytic reactor of cylindrical shape was irradiated by UV-LEDs mounted on 3 panels (16 LEDs on each panel, lambda = 365 nm). The photocatalytic reactor was surrounded by these panels. Measured intensity of light transmission through the reactor varied from 0.2 to 7.5 W/m2,depending on the fluidized bed expansion. The total photocatalytic decompositions of both, acetaldehyde and ethylene were reached in a few minutes with high mineralization degree. Acetaldehyde decomposition was more efficient than ethylene (690 mu g/min versus 80 mu g/min, respectively), due to its good adsorption abilities to the titania surface. Moreover, the activity of utilized bed was stable during prolonged operation time. Thermal imaging camera measurements indicated that the temperature inside the reactor increased when UV-LEDs were lit due to the absorption of UV light by the TiO2 coated EPS, whereas uncoated EPS didn't transfer heat.

TNR@Ni-foam structures were prepared by an alkaline hydrothermal method in an autoclave in a strongly alkaline medium (10 M NaOH) at 150 °C with further acid washing (0.1 M HNO3) and a second hydrothermal treatment in an autoclave at 180 °C. Two TiO2 samples were used for preparation: anatase and P25 of mixed anatase and rutile phases. After the first step of hydrothermal treatment, a layered titanate structure was obtained (Na2Ti3O7). Acid washing caused the substitution of Na+ by H+ and launched the formation of TNR. After the second hydrothermal treatment at 180 °C, for the optimal quantity of acid used for washing (10 mL per 0.75 g of TiO2), titania was crystallized to an anatase phase with small quantities of brookite and rutile. The structures obtained from P25 exhibited more brookite and rutile than those based on the anatase precursor. The morphology of TNR@Ni-foam structures was observed by SEM. The obtained composites were tested for acetaldehyde photodegradation (240 ppm in air) during the continuous flow of gas (5 mL/min) through the reactor coupled with FTIR. The most active samples were those obtained from P25, which had a crystalline structure of TiO2 and contained the lowest quantity of residue Na species.

A comparison of two synthesis methods for depositing Au nanoparticles onto TiO2 was performed: (1) impregnation with HAuCl4 followed by thermal treatment in argon, and (2) magnetron sputtering from a Au disc. The obtained materials were used for acetaldehyde decomposition in a high temperature reaction chamber and ch aracterised by UV-Vis/DR, XPS, XRD, SEM, and photoluminescence measurements. The process was carried out using an air/acetaldehyde gas flow under UV or UV-Vis LED irradiation. The mechanism of acetaldehyde decomposition and conversion was elaborated by in situ FTIR measurements of the photocatalyst surface during the reaction. Simultaneously, concentration of acetaldehyde in the outlet gas was monitored using gas chromatography. All the Au/TiO2 samples showed absorption in the visible region, with a maximum around 550 nm. The plasmonic effect of Au nanoparticles was observed under UV-Vis light irradiation, especially at elevated temperatures such as 100 °C, for Au/TiO2 prepared by the magnetron sputtering method. This resulted in a significant increase in the conversion of acetaldehyde at the beginning, followed by gradual decrease over time. The collected FTIR spectra indicated that, under UV-Vis light, acetaldehyde was strongly adsorbed onto Au/TiO2 surface and formed crotonaldehyde or aldol. Under UV, acetaldehyde was mainly adsorbed in the form of acetate species. The plasmonic effect of Au nanoparticles increased the adsorption of acetaldehyde molecules onto TiO2 surface, while reducing their decomposition rate. The increased temperature of the process enhanced the decomposition of the acetaldehyde.

Volatile organic compounds (VOCs), such as acetaldehyde, are harmful air pollutants, and their efficient removal under dynamic flow conditions remains a challenge. The combination of fluidized bed reactors using cenospheres and photocatalysis is a novel approach that can significantly enhance process efficiency. In this work, TiO2 coated cenospheres, with and without the addition of platinum nanoparticles (NPs), were employed as a photocatalytic fluidized bed. Platinum was deposited on TiO(2)via five cycles of magnetic sputtering, resulting in a Pt loading of approximately 0.23 wt%. Photocatalytic tests for acetaldehyde degradation (800 ppm in air) were carried out under UV-LED irradiation in a continuous-flow reactor at gas flow rates ranging from 80 to 560 ml/ min. The cenospheres had a mean particle diameter of 350.2 +/- 43.0 mu m. SEM and EDS analyses revealed a thin, non-uniform TiO(2)coating with a rough morphology and a uniform distribution of Pt NPs on the TiO(2)surface. Photocatalytic tests showed that TiO2-coated cenospheres without Pt achieved high acetaldehyde decomposition efficiency (up to 99.6 %) at moderate gas flow rates (<= 240 ml/min), but performance decreased at higher flow rates (> 320 ml/min) to 70-90 % degradation. In contrast, Pt-modified composites improved degradation efficiency by approximately 10 % at flow rates of 400-560 ml/min. Elevated temperatures (e.g., 120 degrees C) further increased the degradation rate by an additional 10 %. COQ evolution measurements confirmed higher mineralization efficiency for TiO2/Pt-coated cenospheres. The prepared photocatalytic bed maintained its activity over four consecutive acetaldehyde degradation cycles, underscoring its potential for VOC removal in UV-LEDirradiated fluidized bed reactors.

TiO2 was loaded on the porous nickel foam from the suspended ethanol solution and used for the photocatalytic removal of NOx. Such prepared material was heat-treated at various temperatures (400–600 °C) to increase the adhesion of TiO2 with the support. Obtained TiO2/nickel foam samples were characterized by XRD, UV–Vis/DR, FTIR, XPS, AFM, SEM, and nitrogen adsorption at 77 K. Photocatalytic tests of NO abatement were performed in the rectangular shape quartz reactor, irradiated from the top by UV LED light with an intensity of 10 W/m2. For these studies, a laminar flow of NO in the air (1 ppm) was applied under a relative humidity of 50% and a temperature of 28 °C. Concentrations of both NO and NO2 were monitored by a chemiluminescence NO analyzer. The adsorption of nitrogen species on the TiO2 surface was determined by FTIR spectroscopy. Performed studies revealed that increased temperature of heat treatment improves adhesion of TiO2 to the nickel foam substrate, decreases surface porosity, and causes removal of hydroxyl and alcohol groups from the titania surface. The less hydroxylated surface of TiO2 is more vulnerable to the adsorption of NO2 species, whereas the presence of OH groups on TiO2 enhances the adsorption of nitrate ions. Adsorbed nitrate species upon UV irradiation and moisture undergo photolysis to NO2. As a consequence, NO2 is released into the atmosphere, and the efficiency of NOx removal is decreasing. Photocatalytic conversion of NO to NO2 was higher for the sample heated at 400 °C than for that at 600 °C, although coverage of nickel foam by TiO2 was lower for the former one. It is stated that the presence of titania defects (Ti3+) at low temperatures of its heating enhances the adsorption of hydroxyl groups and the formation of hydroxyl radicals, which take part in NO oxidation. Contrary to that, the presence of titania defects in TiO2 through the formation of ilmenite structure (NiTiO3) in TiO2/nickel foam heated at 600 °C inhibits its photocatalytic activity. No less, the sample obtained at 600 °C indicated the highest abatement of NOx due to the high and stable adsorption of NO2 species on its surface.

A fluidized bed reactor was used for the photocatalytic removal of ethylene to enhance the efficacy of ethylene decomposition through better contact of ethylene molecules with the photocatalyst, which was immobilized on the bed. Expanded polystyrene spheres were used as a bed because they have low densities, which allow one to apply relatively low velocity of flowing gas through the fluidized bed reactor. An expanded polystyrene sphere bed coated with TiO2 and SiO2/TiO2 was used the first time in the photocatalytic decomposition of ethylene. Photoreactor parameters and process conditions were evaluated for this new photocatalytic bed. The advantage of the UV-LED system used for the photocatalytic process was demonstrated. The morphology of the photocatalytic bed spheres was investigated by SEM/EDS images, and the coverage degrees of TiO2 and SiO2 were determined by TG analyses. The highest ethylene decomposition rate was obtained using the PS-SiO2-TiO2 composite (44.5 mu g/min at a flow rate of 240 mL/min and an ethylene feed of 200 ppm in air). The use of a SiO2 semilayer allowed to obtain a more homogeneous TiO2 distribution on the bed. With the UV-LED system, ethylene degradation was 15 times higher than with fluorescent UV lamps, where the energy consumption was comparable.

Expanded polystyrene spheres (EPS) were coated by SiO2–TiO2 or TiO2 for application as a fluidized bed in the photocatalytic reactor. Silica coating was realized by the sol–gel process carried out in a vacuum evaporator at 60–70 °C. The most uniform and thin layer of silica coating was obtained by the Stöber method based on the hydrolysis of tetraethyl orthosilicate (TEOS) catalysed by an ammonia solution. Effective TiO2 coating was obtained by the immersion of EPS in the titania aqueous suspension and evaporation of water in a vacuum evaporator. Heating of EPS spheres coated by SiO2, TiO2 or SiO2–TiO2 at the temperatures of 120–140 °C resulted in a shrinkage of their volume. For the thick layer coating, a strong corrugation of EPS surface was observed. The photocatalytic tests showed, that highly corrugated surface of coated EPS slowed down ethylene decomposition, whereas a thin layer coating of both, SiO2 and TiO2 was advantageous.

The photocatalytic decomposition of ethylene was performed under UV-LED irradiation in the presence of nanocrystalline TiO2 (anatase, 15 nm) supported on porous nickel foam. The process was conducted in a high-temperature chamber with regulated temperature from ambient to 125 °C, under a flow of reacted gas (ethylene in synthetic air, 50 ppm, flow rate of 20 mL/min), with simultaneous FTIR measurements of the sample surface. Ethylene was decomposed with a higher efficiency at elevated temperatures, with a maximum of 28% at 100–125 °C. The nickel foam used as support for TiO2 enhanced ethylene decomposition at a temperature of 50 °C. However, at 50 °C, the stability of ethylene decomposition was not maintained in the following reaction run, but it was at 100 °C. Photocatalytic measurements conducted in the presence of certain radical scavengers indicated that a higher efficiency of ethylene decomposition was obtained due to the improved separation of charge carriers and the increased formation of superoxide anionic radicals, which were formed at the interface of the thermally activated nickel foam and TiO2.

Reduction of TiO2 have been performed under different conditions. Firstly, raw titania was soaked in the ammonia solution at pH = 10, and then was followed the hydrothermal treatment in autoclave at 150 degrees C for 1 h. Such obtained sample was then calcined in Ar at 500-700 degrees C. In the second attitude, hydrothermally prepared TiO2 at 150 degrees C was heat-treated at 500-700 degrees C under flowing of either hydrogen nor ammonia gas. The surface defects in the reduced TiO2 were analyzed by EPR. All the titania samples prepared at low heating temperature such as 500 degrees C showed surface defects in the form of hole traps and oxygen vacancies. With increase temperature of heat-treatment some electron traps and oxygen vacancies increased. Sample with the highest amount of the reduced Ti3+ centers was obtained at 600 degrees C under H2 treatment. This sample showed the highest yield in H2 production during water splitting under simulated solar light and the highest generation of photocurrent at & lambda; = 388 nm. Formation of Ti3+ conducts to the narrowing of the titania band gap and can increase harvesting of the solar light. The presence of both, reduced anatase and rutile in TiO2 prepared at 600 degrees C under H2 could increase photoelectrons conductivity due to the photoelectron transfer between anatase and rutile particles. Moreover, the presence of Ti3+ could increase adsorption of water on TiO2 surface and improve the photocatalytic yield of water splitting. Hydrogen appeared to be a stronger reducing agent than ammonia gas.

This study presents a relatively low-cost method for modifying TiO2-based materials for photocatalytic bacterial inactivation. The photocatalytic inactivation of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria using modified sulphated TiO2 was studied. The modification focused on the reduction of TiO2 by ammonia agents and hydrogen at 400–450 °C. The results showed a high impact of sulphate species on the inactivation of E. coli. The presence of these species generated acid sites on TiO2, which shifted the pH of the reacted titania slurry solution to lower values, around 4.6. At such a low pH, TiO2 was positively charged. The ammonia solution caused the removal of sulphate species from TiO2. On the other hand, hydrogen and ammonia molecules accelerated the removal of sulphur species from TiO2, as did heating it to 450 °C. Total inactivation of E. coli was obtained within 30 min of simulated solar light irradiation on TiO2 heat-treated at 400 °C in an atmosphere of Ar or NH3. The S. epidermidis strain was more resistant to photocatalytic oxidation. The contact of these bacteria with the active titania surface is important, but a higher oxidation force is necessary to destroy their cell membrane walls because of their thicker cell wall than E. coli. Therefore, the ability of a photocatalyst to produce ROS (reactive oxidative species) will determine its ability to inactivate S. epidermidis. An additional advantage of the studies presented is the inactivation of bacteria after a relatively short irradiation time (30 min), which does not often happen with photocatalysts not modified with noble metals. The modification methods presented represent a robust and inexpensive alternative to photocatalytic inactivation of bacteria.

Photocatalytic decomposition of ethylene was performed under UV-Led irradiation at the presence of nanocrystalline TiO2 (anatase, 15 nm) supported on the porous nickel foam. Process was carried out in the high temperature chamber with regulated temperature from ambient to 125°C under flow of reacted gas (ethylene in a synthetic air, 50 ppm) with simultaneous FTIR measurements of sample surface. Ethylene was decomposed with higher efficiency in elevated temperatures with maximum of 28% at 100-125°C. The nickel foam used as support for TiO2 allowed to enhance the ethylene decomposition at the temperature of 50°C. However, at 50°C the stability of ethylene decomposition was not retained within the following reaction run, but it was at 100°C. Performed photocatalytic measurements at the presence of some radicals scavengers indicated that higher efficiency of ethylene decomposition was obtained due to the improved separation of charge carriers and increased formation of superoxide anionic radicals, which were formed at the interface of thermally activated nickel foam and TiO2.

Acetaldehyde decomposition was performed under heating at a temperature range of 25–125 °C and UV irradiation on TiO2 doped by metallic Ni powder and TiO2 supported on nickel foam. The process was carried out in a high-temperature reaction chamber, “The Praying MantisTM”, with simultaneous in situ FTIR measurements and UV irradiation. Ni powder was added to TiO2 in the quantity of 0.5 to 5.0 wt%. The photothermal measurements of acetaldehyde decomposition indicated that the highest yield of acetaldehyde conversion on TiO2 and UV irradiation was obtained at 75 °C. The doping of nickel to TiO2 did not increase its photocatalytic activity. Contrary to that, the application of nickel foam as a support for TiO2 appeared to be highly advantageous because it increased the decomposition of acetaldehyde from 31 to 52% at 25 °C, and then to 85% at 100 °C in comparison with TiO2 itself. At the same time, the mineralization of acetaldehyde to CO2 doubled in the presence of nickel foam. However, oxidized nickel foam used as support for TiO2 was detrimental. Most likely, different mechanisms of electron transfer between Ni–TiO2 and NiO-TiO2 occurred. The application of nickel foam greatly enhanced the separation of free carriers in TiO2. As a consequence, high yields from the photocatalytic reactions were obtained.

Preparation of TiO2 with Ti3+ defects was performed by heating of titania raw material under flow of an ammonia gas at the temperatures of 300-700 ?. Different types of surface defects have been formed in titania upon heat treatment process and they were analysed by EPR technique. Enhanced formation of hydroxyl radicals was observed under both UV and visible light irradiations, on TiO2 sample prepared at 700 ?, which contained inner Ti3+ centers and oxygen vacancies in rutile lattice sites. The most probably the presence of rutile defects increased formation of O-2(-& BULL;) radicals, which then gave yield in H2O2 and further in hydroxyl radicals. The intra band gap was created in rutile due to the formation of inner Ti3+ centers, which enhanced its visible light activity.

Preparation of TiO2 using the hydrothermal treatment in NH4OH solution and subsequent thermal heating at 500–700 °C in Ar was performed in order to introduce some titania surface defects. The highest amount of oxygen vacancies and Ti3+ surface defects were observed for a sample heat-treated at 500 °C. The presence of these surface defects enhanced photocatalytic properties of titania towards the deactivation of two bacteria species, E. coli and S. epidermidis, under artificial solar lamp irradiation. Further modification of TiO2 was targeted towards the doping of Cu species. Cu doping was realized through the impregnation of the titania surface by Cu species supplied from various copper salts in an aqueous solution and the subsequent heating at 500 °C in Ar. The following precursors were used as a source of Cu: CuSO4, CuNO3 or Cu(CH3COO)2. Cu doping was performed for raw TiO2 after a hydrothermal process with and without NH4OH addition. The obtained results indicate that Cu species were deposited on the titania surface defects in the case of reduced TiO2, but on the TiO2 without NH4OH modification, Cu species were attached through the titania adsorbed hydroxyl groups. Cu doping on TiO2 increased the absorption of light in the visible range. Rapid inactivation of E. coli within 30 min was obtained for the ammonia-reduced TiO2 heated at 500 °C and TiO2 doped with Cu from CuSO4 solution. Photocatalytic deactivation of S. epidermidis was greatly enhanced through Cu doping on TiO2. Impregnation of TiO2 with CuSO4 was the most effective for inactivation of both E. coli and S. epidermidis.

Removal of C2H4 in the air was carried out in the continuous flow reactor with the photocatalytic bed (expanded polystyrene spheres coated by TiO2 or SiO2/TiO2) under irradiation of UV light. Continuous flow of a gas stream through the reactor was realised at the static bed and under bed fluidization. The required flow of a gas stream through the reactor for bed fluidisation was 500–700 ml/min, whereas for the static bed the flow rate of 20 ml/min was used. Fluidized bed reactor appeared to be much more efficient in ethylene removal than that with the stationary bed. It was caused by the increased speed of C2H4 mass transfer to the photocatalyst surface and better utilization of the incident UV light. In the fluidized bed reactor calculated rate of C2H4 degradation was around 10 μg/min whereas in the stationary state 1.2 μg/min only.

The titania pulp—a semi product received from the industrial production of titania white—was submitted for the thermal heating at 400–600 °C under Ar and H2 to obtain TiO2 with different structure and oxygen surface defects. Heating of titania in H2 atmosphere accelerated dehydration and crystallisation of TiO2 compared to heating in Ar. TiO2 prepared at 500 and 600 °C under H2 had some oxygen vacancies and Ti3+ centres (electron traps), whereas TiO2 obtained at 450 °C under H2 exhibited some hole traps centres. The presence of oxygen vacancies induced adsorption of atmospheric CO2. It was evidenced, that ethylene reacted with TiO2 after UV irradiation. Formic acid was identified on TiO2 surface as the reaction product of ethylene oxidation. Hydroxyl radicals were involved in complete mineralisation of ethylene. TiO2 prepared at 500 °C under H2 was poorly active because some active sites for coordination of ethylene molecules were occupied by CO2. The most active samples were TiO2 with high quantity of OH terminal groups. At 50 °C, the physically adsorbed water molecules on titania surface were desorbed, and then photocatalytic decomposition of ethylene was more efficient. TiO2 with high quantity of chemisorbed OH groups was very active for ethylene decomposition. The acidic surface of TiO2 enhances its hydroxylation. Therefore, it is stated that TiO2 having acidic active sites can be an excellent photocatalyst for ethylene decomposition under UV light.

The aim of the research was to determine how the admixture of nanosilica affects the structure and mechanical performance of cement concrete exposed to high temperatures (200, 400, 600, and 800 °C). The structural tests were carried out on the cement paste and concrete using the methods of thermogravimetric analysis, mercury porosimetry, and scanning electron microscopy. The results show that despite the growth of the cement matrix’s total porosity with an increasing amount of nanosilica, the resistance to high temperature improves. Such behavior is the result of not only the thermal characteristics of nanosilica itself but also of the porosity structure in the cement matrix and using the effective method of dispersing the nanostructures in concrete. The nanosilica densifies the structure of the concrete, limiting the number of the pores with diameters from 0.3 to 300 μm, which leads to limitation of the microcracks, particularly in the coarse aggregate-cement matrix contact zone. This phenomenon, in turn, diminishes the cracking of the specimens containing nanosilica at high temperatures and improves the mechanical strength.

TiO2 was placed in heat-treatment at the temperature of 400–500 °C under flow of hydrogen gas in order to introduce some titania surface defects. It was observed that hole centers in TiO2 were created during its heat treatment up to 450 °C, whereas at 500 °C some Ti3+ electron surface defects appeared. The type of titania surface defects had a great impact on the mechanism of acetaldehyde decomposition under irradiation of artificial visible light. Formation of O•− defects improved both acetaldehyde decomposition and mineralization due to the increased oxidation of adsorbed acetaldehyde molecules by holes. Contrary to that, the presence of electron traps and oxygen vacancies in titania (Ti3+ centers) was detrimental for its photocatalytic properties towards acetaldehyde decomposition. It was proved that transformation of acetaldehyde on the TiO2 with Ti3+ defects proceeded through formation of butene complexes, similar as on rutile-type TiO2. Formed acetic acid, upon further oxidation of butene complexes, was strongly bound with the titania surface and showed high stability under photocatalytic process. Therefore, titania sample heat-treated with H2 at 500 °C showed much lower photocatalytic activity than that prepared at 450 °C. This study indicated the great impact of titania surface defects (hole traps) in the oxidation of acetaldehyde and opposed one in the case of defects in the form of Ti3+ and oxygen vacancies. Oxidation abilities of TiO2 seem to be important in the photocatalytic decomposition of volatile organic compounds (VOCs) such as acetaldehyde.