TiO2-coated Glass Research Articles

Degradation of methyl orange using hydrodynamic Cavitation, H2O2, and photo-catalysis with TiO2-Coated glass Fibers: Key operating parameters and synergistic effects

Advanced oxidation processes (AOPs) are eco-friendly, and promising technology for treating dye containing wastewater. This study focuses on investigating the removal of methyl orange (MO), an azo dye, from a synthetic wastewater through the use of hydrodynamic cavitation (HC), both independently and in combination with hydrogen peroxide (H2O2), as an external oxidant, as well as photocatalysis (PC) employing catalyst coated on glass fibers tissue (GFT). The examination of various operating parameters, including the pressure drop and the concentration of H2O2, was systematically conducted to optimize the degradation of MO. A per-pass degradation modelwas used to interpret and describe the experimental data. The data revealed that exclusive employment of HC using a vortex-based cavitation device at 1.5 bar pressure drop, resulted in a degradation exceeding 96 % after 100 passes, equivalent to 230 min of treatment (cavitation yield of 3.6 mg/kJ for HC), with a COD mineralization surpassing 12 %. The presence of a small amount of H2O2 (0.01 %) significantly reduced the degradation time from 230 min to 36 min (16 passes), achieving a degradation of 99.8 % (cavitation yield of 6.77 mg/kJ for HC) with COD mineralization rate twice as much as HC alone, indicating a synergistic effect of 4.8. The degradation time was further reduced to 21 min by combining HC with PC using TiO2-coated glass fibers and H2O2, (cavitation yield of 11.83 mg/kJ for HC), resulting in an impressive synergistic effect of 9.2 and COD mineralization twice as high as the HC/H2O2 system. The results demonstrate that HC based hybrid AOPs can be very effective for treating and mineralizing azo dyes in water.

Insights from experiment and machine learning for enhanced TiO2 coated glazing for photocatalytic NOx remediation

TiO2-coated glass for photocatalytic NOx removal was optimised. Correlations between the synthesis parameters, coating properties, and photocatalytic activity was systematically studied through experimentation and machine learning tools for the first time.

Structural properties and photocatalytic activity of amorphous-crystalline TiO2 thin films

TiO2-coated glass plates were prepared by dip coating using TiO2 coating sol with a mixed amorphous and crystalline structure. These samples were dried at 100°C or calcined at 500°C, which were referred to as MT and CT, respectively. The TiO2 thin films on glass plates were characterized by X-ray diffraction, thermogravimetry-differential thermal analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy, and ultraviolet–visible diffuse reflectance spectra. The TiO2 thin films of MT samples had mixed amorphous and crystalline structures, while those of CT samples had only crystalline structures. The photocatalytic activity of the samples was investigated on the basis of methylene blue (MB) decomposition under ultraviolet and visible light irradiation. In the dark stabilization, MT samples had a higher MB adsorption capacity than CT samples. MT samples had a smaller amount of anatase TiO2 than CT samples, but both glass plate samples showed the same MB photocatalytic activity under ultraviolet light irradiation. We presumed that these results were because the amorphous-crystalline TiO2 thin films had a high specific surface area, so they had more adsorption and active sites. Under visible light irradiation, only the MT samples had photocatalytic activity, which can be attributed to their high visible light absorbance, which may be due to their peroxo groups, disordered structure, and larger specific surface area.

Preparation and Characterization of TiO2-Coated Hollow Glass Beads for Functionalization of Deproteinized Natural Rubber Latex via UVA-Activated Photocatalytic Degradation.

The photochemical degradation of natural rubber (NR) is a prevalent method used to modify its inherent properties. Natural rubber, predominantly derived from the Hevea Brasiliensis tree, exhibits an exceptionally high molecular weight (MW), often reaching a million daltons (Da). This high MW restricts its solubility in various solvents and its reactivity with polar compounds, thereby constraining its versatile applications. In our previous work, we employed TiO2 in its powdered form as a photocatalyst for the functionalization of NR latex. However, the post-process separation and reuse of this powder present substantial challenges. In this present study, we aimed to functionalize deproteinized NR (DPNR) latex. We systematically reduced its MW via photochemical degradation under UVA irradiation facilitated by H2O2. To enhance the efficiency of the degradation process, we introduced TiO2-coated hollow glass beads (TiO2-HGBs) as photocatalysts. This approach offers the advantage of easy collection and repeated reuse. The modified DPNR showed a reduction in its number-average MW from 9.48 × 105 to 0.28 × 105 Da and incorporated functional groups, including hydroxyl, carbonyl, and epoxide. Remarkably, the TiO2-HGBs maintained their performance over seven cycles of reuse. Due to their superior efficacy, TiO2-HGBs stand out as promising photocatalysts for the advanced functionalization of NR across various practical applications.

Photocatalytic Degradation of Textile Dyeing Wastewater Using Titanium Dioxide on a Fixed Substrate: Optimization of Process Parameters and Continuous Reactor Tests

Herein, a preparation of a mixed-phase titanium dioxide (TiO2) thin layer on glass beads was developed using the modified spray method. This approach was determined to be affordable and easy to operate. Optimum conditions were investigated for the photodegradation of wastewater generated from textile dyeing by TiO2-coated glass beads as a catalyst using the central composite design (CCD). An increase in the direct dye photodegradation rate was observed at lower direct dye concentrations when TiO2 dosages were increased, and the initial pH value was decreased. The optimal conditions involving TiO2 dosage, pH, UV intensity, and dye concentrations were 3 g/L, 5.0, 3000 µW/cm2, and 50 mg/L, respectively, when administered at ambient temperatures. For the batch experiments, the direct dye removal efficiency at 93.7% was achieved within 24 h. The average direct dye removal efficiency was 67.8% and could be up to 80.2% when using a fixed-bed photocatalysis reactor during 30 d of continuous operation. The reused catalyst’s degradation efficiency was not significantly changed, indicating its capability for repeated reuse and the excellent stability of immobilized TiO2 onto the glass beads. This study additionally found that high temperatures could increase the efficiency of color removal.

Preparation of TiO2-coated glass flat membrane and its photocatalytic degradation of methylene blue

A polymer-glass flat membrane was prepared using the phase inversion casting method and TiO2 was coated on the surface of the membranes. After drying and calcination, obtained membrane was used for the photocatalytic degradation of methylene blue. The membrane was characterized and the photocatalytic degradation of methylene blue by the membrane was investigated. The results showed that the membranes were uniformly coated without exfoliation. The membrane coated by three layers TiO2 sol exhibited the best photocatalytic degradation performance for methylene blue. Compared to the pristine membrane, the photocatalytic degradation effect of the coated membrane was effectively improved by up to 98.5%. Additionally, the membrane could be continuously recycled. After five cycles, the degree of photocatalytic removal of methylene blue remained 92%. Moreover, the membrane exhibited a good acid and alkali corrosion resistance. The membrane can be repeatedly used for the high efficiency photocatalytic removal of methylene blue.

Degradation of Emerging Pollutants by Photocatalysis: Radiation Modeling and Kinetics in Packed-Bed Reactors

Radiation modeling and kinetics in two different packed-bed reactors filled with TiO2-coated glass rings are presented. The first reactor was cylindrical, irradiated from one end by a 150 W mercury lamp. It was employed to obtain the values of the intrinsic kinetic parameters of the degradation of the emerging contaminant clofibric acid (CA). The expression to represent the kinetics of the pollutant was derived from a proposed reaction scheme, and it includes explicitly the effect of photon absorption rate on the reaction rate. The second reactor was annular, irradiated internally and externally by 40 UV-LED lamps. The kinetic parameters calculated in the first reactor were directly employed to simulate the performance of the second one, without using any adjustable parameter. The Monte Carlo method was applied to solve the radiation models in both reactors. Good agreement was obtained between simulation results and experimental data under different operating conditions, with a percentage root-mean-square error of 4.6%. The kinetic parameters proved to be independent of the irradiation source, reactor geometry, and catalyst film thickness, and can be readily applied to design real scale devices.

Radiation modeling and performance evaluation of a UV-LED photocatalytic reactor for water treatment

A photocatalytic reactor under UV-LED illumination is presented. It is an annular, packed-bed reactor filled with TiO2-coated glass rings. The reactor is irradiated both internally and externally in order to minimize the presence of dark zones. The knowledge of the radiation distribution inside the reactor is a key aspect to optimize its design and improve its efficiency. A three-dimensional model has been developed to describe the distribution of the local rate of photon absorption inside the reactor. The Monte Carlo method was applied to solve the radiation model. Simulation results were validated with experimental measurements. The model was able to predict the influence of the catalyst film thickness and the illumination conditions on the radiation distribution and on the total rate of photon absorption. Also, degradation assays of the pharmaceutical clofibric acid were carried out in the reactor and the performance of different illumination conditions was evaluated by means of the quantum efficiency parameter.

Photocatalytic Inactivation of Viruses and Prions: Multilevel Approach with Other Disinfectants

Ag, Cu, Zn, Ti, and Au nanoparticles show enhanced photocatalytic properties. Efficient indoor disinfection strategies are imperative to manage the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Virucidal agents, such as ethanol, sodium hypochlorite, 222-nm UV light, and electrolyzed water inactivate SARS-CoV-2 in indoor environments. Tungsten trioxide (WO3) photocatalyst and visible light disinfect abiotic surfaces against SARS-CoV-2. The titanium dioxide (TiO2)/UV system inactivates SARS-CoV-2 in aerosols and on deliberately contaminated TiO2-coated glass slide surfaces in photocatalytic chambers, wherein 405-nm UV light treatment for 20 min sterilizes the environment and generates reactive oxygen species (ROS) that inactivate the virus by targeting S and envelope proteins and viral RNA. Mesoscopic calcium bicarbonate solution (CAC-717) inactivates pathogens, such as prions, influenza virus, SARS-CoV-2, and noroviruses, in fluids; it presumably acts similarly on human and animal skin. The molecular complexity of cementitious materials promotes the photocatalysis of microorganisms. In combination, the two methods can reduce the pathogen load in the environment. As photocatalysts and CAC-717 are potent disinfectants for prions, disinfectants against prionoids could be developed by combining photocatalysis, gas plasma methodology, and CAC-717 treatment, especially for surgical devices and instruments.

TiO2-coated glass hollow fiber membranes: preparation and application for photocatalytic methylene blue removal

A glass hollow fiber membrane coated with TiO2 was successfully synthesized by dip-coating and calcination. In addition, the effects of the calcination temperature, number of coating layers, and treatment method on the photocatalytic removal of methylene blue from wastewater by the membrane were investigated. The results showed that the TiO2-coated membrane calcined at 550 °C was uniform. It showed good photocatalytic and anti-fouling properties. As compared to the basement membrane, the TiO2-coated membrane showed significantly improved photocatalytic removal of methylene blue. It showed a methylene blue removal degree as high as 97.2% and could be recycled multiple times by a simple treatment. The methylene blue removal degree of the membrane remained 92.3-93.6% after five recycling operations. Therefore, the membrane prepared via the simple method proposed in this study could be used as an efficient photocatalyst to remove methylene blue from wastewater.

Mechanical Stability Is Key for Large-Scale Implementation of Photocatalytic Surface-Attached Film Technologies in Water Treatment

Replacement of classical tertiary water treatment by chemical-free sunlight-driven photocatalytic units has been often proposed. Photocatalysts are required to be cost-effective, inert, chemically stable, reusable, and easy to separate and also that they are mechanically stable. The effect of mechanical stress on a photoactive TiO2 layer, and on its effectivity for degradation of phenol as a model pollutant, has been studied during photocatalytic water treatment using NUV–vis light. Sol–gel (SG) and liquid phase deposition (LPD) methods have been used to coat spherical glass beads with the photocatalyst (TiO2). Physicochemical characterization of coated glass beads has been performed by N2 adsorption–desorption isotherms, SEM, EDXS, and AFM. Phenol photocatalyzed degradation was carried out both in stirred batch and flow reactors irradiated with a medium-pressure Hg-vapor lamp (λ > 350 nm). Phenol concentration was determined by HPLC, and its photoproducts were identified using HPLC/MS. In the stirred batch reactor, all LPD-coated glass beads displayed higher catalytic activity than SG-coated ones, which increased with calcination temperature, 700°C being the most efficient temperature. Preliminary etching of the glass beads surface yielded dissimilar results; whereas, phenol photodegradation with SG-coated etched glass beads is twice faster than with unetched SG ones, the rate reduces to one-third using LPD etched instead of unetched LPD glass beads. Phenol photodegradation using LPD is similar both in stirred batch and flow reactors, despite the latter uses a lower catalyst load. LPD-etched catalyst was recovered and reused in the stirred batch reactor; its activity reduced sharply after the first use, and it also lost activity in successive runs, ca. 10% of activity after each “use and recover” cycle. In the flow reactor, activity loss after the first experiment and recycling (ca. 30%) was much larger than in the following runs, where the activity remained rather constant through several cycles. LPD is more adequate than SG for TiO2 immobilization onto glass beads, and their calcination at 700°C leads to relatively strong and reactive photocatalytic films. Still, TiO2-coated glass beads exhibited very low photoactivity compared to TiO2-P25 nanoparticles, though their separation is much easier and almost costless. The durability of the catalytic layer increases when using a flow reactor, with the pollutant solution flowing in a laminar regime through the photocatalyst bed. In this way, the abrasion of the photocatalytic surface is largely reduced and its photoactivity is better maintained.

Adhesive Wet Metallization on TiO2-Coated Glass

In this study, a process for wet metallization on glass substrate involving adhesive electroless plating (ELP) is developed by integrating two material innovations. The first involves functionalizing a polymer-capped Pd nanocluster with amino silane compound to strengthen the adhesion between the ELP metal film and substrate. The second involves an additional nanoscaled TiO2 layer serving as the adhesion promoting layer (APL) coated on glass before metallization. After investigation with various tools, ELP metal film was observed to penetrate the mesoporous structure of TiO2 APL, reinforcing the adhesion of metallized film on glass through the mechanical anchoring effect. The formation of an interlayer between TiO2 APL and glass is not observed. A T-peel strength of 325 N m−1 is achieved. According to fracture analysis, the metal film/TiO2/glass structure breaks inside TiO2 APL, not TiO2 APL/glass, suggesting that further engineering developments are required to improve TiO2 APL coating.

Microwave radiation induced performance modifications of dye-sensitized solar cells

Natural dye from Argemone mexicana flower is used as the photosensitizer for fabricating dye-sensitized solar cells (DSSCs). The cells were fabricated using TiO2 as the semiconducting layer deposited on the transparent fluorine-doped tin oxide (FTO) conductive glass. Microwave processing is used for annealing the TiO2-coated FTO glass. The UV–Vis absorption spectra, FTIR and Raman Spectral studies were carried out to check the suitability of the dyes. The I–V characteristic curves of all the fabricated DSSCs were measured and analyzed. The photovoltaic parameters, short-circuit current (I sc), open-circuit voltage (V oc), fill factor (FF) and efficiency (η) of microwave annealed DSSCs are calculated and reported in this paper. Optimum values were observed for solar cells prepared with blocking layer and irradiated with microwave for 7 min, short-circuit current = 2.71 mA, open-circuit voltage = 0.47 mV, fill factor=0.54 and efficiency = 0.69.

Design and performance evaluation of a photocatalytic reactor for indoor air disinfection.

Since COVID-19 pandemic, indoor air quality control has become a priority, and the development of air purification devices effective for disinfecting airborne viruses and bacteria is of outmost relevance. In this work, a photocatalytic device for the removal of airborne microorganisms is presented. It is an annular reactor filled with TiO2-coated glass rings and irradiated internally and externally by UV-A lamps. B. subtilis spores and vegetative cells have been employed as model biological pollutants. Three types of assays with aerosolized bacterial suspensions were performed to evaluate distinct purification processes: filtration, photocatalytic inactivation in the air phase, and photocatalytic inactivation over the TiO2-coated rings. The radiation distribution inside the reactor was analysed by performing Monte Carlo simulations of photon absorption in the photocatalytic bed. Complete removal of a high load of microorganisms in the air stream could be achieved in 1 h. Nevertheless, inactivation of retained bacteria in the reactor bed required longer irradiation periods: after 8 h under internal and external irradiation, the initial concentration of retained spores and vegetative cells was reduced by 68% and 99%, respectively. Efficiency parameters were also calculated to evaluate the influence of the irradiation conditions on the photocatalytic inactivation of bacteria attached at the coated rings.

Enhanced Photocatalytic Degradation of Caffeine Using Titanium Dioxide Photocatalyst Immobilized on Circular Glass Sheets under Ultraviolet C Irradiation

This work presents the development of titanium dioxide (TiO2) film immobilized on circular glass sheets for photocatalytic degradation of caffeine under ultraviolet C (UVC) irradiation. TiO2 was synthesized through the ultrasonic-assisted sol–gel method and immobilized on circular glass sheets by the doctor blade technique. Polyvinylpyrrolidone (PVP) was used to mix with the TiO2 precursor solution to enhance film adhesion on the glass surface. TiO2 film was mainly composed of anatase phase with a small amount of rutile phase. Caffeine removal was found to increase with increasing irradiation time. Caffeine (20 mg/L) in the synthetic wastewater could not be detected after 3 h of UVC irradiation. The reaction rate of caffeine degradation followed the pseudo-first-order model. The concentrated caffeine solutions required a longer irradiation time for degradation. The used TiO2-coated glass sheets could be easily separated from the treated wastewater and reusable. The caffeine removal efficiency of TiO2-coated glass sheets in each cycle maintained a high level (~100%) during fifteen consecutive cycles.

Preparation and Properties of TiO2-Coated Hollow Glass Microspheres as Thermal Insulation Materials for Energy-Saving Buildings

A hollow glass microsphere (HGM)/TiO2 composite hollow sphere was successfully prepared via a simple precipitation method. The TiO2 coating layers grew on the surface of the HGMs that range from 20 to 50 μm in diameter as nanoparticles with the formation of the Si‒O‒Ti bonds. The growth mechanism accounting for the formation of the TiO2 nanolayers was proposed. The morphology, composition, thermal insulation properties, and visible–near infrared (VIS–NIR) reflectance of the HGMs/TiO2 composite hollow spheres were characterized. The VIS–NIR reflectance of the HGMs/TiO2 composite hollow spheres increased by more than 30% compared to raw HGMs. The thermal conductivity of the particles is 0.058 W/(m K). The result indicates that the VIS–NIR reflectance of the composite hollow spheres is strongly influenced by the coating of TiO2. The composite hollow spheres were used as the main functional filler to prepare the organic–inorganic composite coatings. The glass substrates coated by the organic–inorganic coatings had lower thermal conductivity and higher near infrared reflectivity. Therefore, the HGMs/TiO2 composite hollow spheres can reflect most of the solar energy and effectively keep out the heat as a thermal insulation coating for energy-saving constructions.

Capillary microphotoreactor packed with TiO2-coated glass beads: An efficient tool for photocatalytic reaction

A novel capillary microphotoreactor (MPR) packed with TiO2-coated glass beads was developed in this work and its photocatalytic performance was evaluated using degradation of methylene blue (MB) as a model reaction. As compared to conventional wall-coated MPR, the use of glass beads as packing material not only provides a larger surface area for catalyst immobilization and shortens the mass transfer route, but also introduces flow perturbation. An appropriate size of glass beads should be chosen for packing because there is a tradeoff between increased catalysts coating area and decreased light penetration. It was found out that nearly 100 % degradation efficiency could be achieved in 80# glass beads packed MPR within short residence time (20 s), which was more than 2 orders of magnitude larger than value obtained in wall-coated MPR under the same operational conditions. Moreover, the packed MPR showed good durability, which declined by about 17 % after 6 h of operation and then remained stable for next 19.5 h.

Photodetector Characterization Based on DSSC (Dye-Sensitized Solar Cell)

A photodetector performance as a light sensor based on the design and material of DSSC (Dye-Sensitized Solar Cell) has been characterized. Oxide Semiconductor nanoparticle of TiO2 and extracted natural dye are used to absorb and convert incident photon to electric energy using a sandwich structure of 1.5 x 1.5 cm2 active area. The sensor materials were used include TCO (Transparent Conductive Oxide) glass as substrate, electrolyte solution and carbon. Method of TiO2 deposition to the TCO glass substrate is spin coating and firing at 1,500 rpm and 450 °C, respectively. Natural dye was extracted from green algae by a different variation of solution concentration according to the ratio of mass and volume. The chlorophyll absorbance was investigated by spectrophotometer at a wavelength of 300-800 nm. SEM (Scanning Electron Microscope) is used to observe TiO2-coated TCO glass morphology. Fabricated sensors are characterized according to the electrical parameters of voltage and current towards light illuminance from the light source. This natural dye-based optical photodetector performance has been analysed to obtain linearity, sensitivity, uncertainty error, and other electrical transient response characteristics. The result of extracted chlorophyte absorbance shows a wavelength peak at 580 to 680 nm with different intensity; it indicates the visible light absorbance spectra occurred. Sensor measurement using light illumination up to 30,000 lux produces the highest rated voltage of 626.4 mV and current 78,7 (µA) at the ratio of 6:5 (m:v) solution. This sensor has a voltage sensitivity of 1,0875 mV/10lux and the current sensitivity of 0.0024 µA/lux. The voltage and current uncertainty error are 0.36% and 0.481%, respectively.

Removal of Organic Micropollutants from a Municipal Wastewater Secondary Effluent by UVA-LED Photocatalytic Ozonation

Numerous contaminants of emerging concern (CECs) have been found in different water bodies. Directive 2013/39/EU and Decision 2018/840/EU are consequently being implemented in the field of water policies. Twelve CECs (e.g., isoproturon, ciprofloxacin, and clarithromycin are among those listed) were detected in a municipal wastewater secondary effluent by means of solid phase extraction and ultra-high-performance liquid chromatography with tandem mass spectrometry (SPE-UHPLC-MS/MS). Different advanced oxidation processes (AOPs), based on the combination of ozone, UVA-LED and powdered TiO2, were investigated for their removal in a semi-batch operation. In addition, TiO2-coated glass rings (P25R) were characterized with different techniques (SEM, WDXRF) and used for continuous mode operation in a packed bed reactor (PBR). Among the AOPs studied, ozone-based processes were found to be more efficient than heterogeneous photocatalysis. A kinetic study was performed showing that direct ozonation is the main oxidation pathway for CEC removal. Ozone was successfully decomposed in combination with UVA-LED and P25R, resulting in an apparent rate constant of 3.2 × 10−2 s−1 higher than in the O3/LED system (1.0 × 10−3 s−1) or with ozone alone (8.6 × 10−5 s−1). Hydroxyl radical reaction could prevail over direct ozone reaction for the most refractory compounds (e.g., isoproturon).

Photomask-Free, Direct Selective Electroless Deposition on Glass by Controlling Surface Hydrophilicity.

This paper reports a new approach to realize direct selective electroless deposition (ELD) without the requirement of photolithography. This method involves sequential silane-compound modifications in which the first modification creates a hydrophobic surface on the TiO2-coated glass using a fluorine-rich alkoxysilane compound, followed by a laser ablation to create the pattern. Then, the entire substrate is immersed into an aqueous solution containing amino-silane equipped Pd nanoparticles for the second modification. Because most substrate surface is hydrophobic, the amino-silane-equipped Pd catalysts can only graft on the laser-ablated zone to accomplish selective ELD.