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The application of photocatalysts in concrete technology is by now a well-established concept. However, despite the great opportunities for air quality improvements to be derived from the considerable concrete surfaces exposed to the atmosphere, particularly in cities where air quality is greatly affected by vehicle exhaust and industrial emissions...
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Methods: We elaborately developed a fatigue driving detecti...
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... Recently, heterogeneous semiconductor photocatalysis is gaining popularity for its potential to convert organic pollutants into non-toxic CO 2 and H 2 O when exposed to light [12,13,14,15,16,17]. This mechanism is based on the production of electron-hole pairs in response to light exposure, which results in the formation of highly reactive species such as hydroxyl radicals (•OH) that promote the oxidative destruction of pollutants [18,19,20].Although numerous semiconductor photocatalysts that respond to ultraviolet light have been developed and investigated [21,22,23], visible-light-active materials are becoming increasingly significant for energy-efficient applications. The low bandgap energy, chemical stability and non-toxicity of samarium oxide (Sm 2 O 3 ), a rare-earth metal oxide, render it a viable visible-light-driven photocatalyst [24][25]. ...
By using a solvothermal preparation process, a multi-walled carbon nanotube photocatalyst (Sm2O3/MWCNT) was synthesises, which improved the photocatalytic efficiency of samarium oxide (Sm2O3) and revealed its catalytic mechanism. The crystalline phase and morphological structure of Sm2O3/MWCNTs were observed using X-ray powder diffraction spectroscopy (XRD), Raman spectra, Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) revealed that the modification by MWCNTs resulted in modifications in functional groups on the surface and a binding energy shift of Sm and O. The catalytic performance of Sm2O3/MWCNT was enhanced in all of the characterisations. The Sm2O3/MWCNT-catalysed degradation routes of Orange G and Hydroquinone dyes were investigated as the target trace persistent pollutant. Throughout the end, preliminary studies were conducted to ascertain the extent to which pH, catalyst dosage, beginning dye concentration, and electrolytes affected catalyst efficiency in the process of dye degradation. Research on the reusability of the catalyst showed that it retained its original efficiency even after the third cycle of reuse.
Graphical Abstract
... Samsudin et al. [4] used bismuth vanadate (BiVO 4 ) as a photocatalyst for wastewater treatment to promote the development of BiVO 4 photocatalyst. Yang et al. [5] prepared various quartz-loaded TiO 2 composites. They confirmed the existence of Ti O Si chemical bonds and observed that TiO 2 accumulated on the surface in the form of multiple agglomerated layers. ...
Organic dyes and drug‐resistant bacteria are posing a potential threat to human health and ecology. Graphite phase carbon nitride (g‐C3N4), because of its good light absorption performance, stability, and suitable energy band structure, has potential applications in photocatalysis. Herein, oxygen doped carbon nitride (O‐CN) and MXene Ti3C2 (TC) were physically mixed to form a heterojunction. The effect of the ratio between O‐CN and TC on the photocatalytic performance was studied. Then O‐CN/TC‐2 was dispersed in PVA solution. Subsequently, the mixed solution was electrospinning into flexible nanofiber membranes POCNTC‐2. POCNTC‐2 composite nanofiber membranes were smooth and uniform, and the average diameter of the nanofiber was 390 ± 2.7 nm. The maximum removal efficiency of the composite nanofiber membrane for MB solution (10 mg/L) reached 94.1% within 240 min. Meanwhile, it had favorable cycle stability. According to the bacteriostatic results, the maximum bacteriostatic zone diameters of POCNTC‐2 8% against Escherichia coli and Staphylococcus aureus could reach 24 ± 0.2 and 16 ± 0.2 mm, respectively, and the bacteriostatic rates could reach 92% and 87%, respectively. Overall, the excellent photocatalytic removal of organic materials and antibacterial properties gave the flexible POCNTC membrane great application potential in the field of environmental purification.
... There are two primary methods for preparing photocatalytic concrete: spraying, and internal mixing. However, concrete prepared using the spraying method suffers from loss of TiO 2 particles under external factors such as wear and rainfall, leading to a decrease in catalytic performance (Yang et al. 2018). Previous studies have shown that the catalytic performance of the photocatalytic products prepared using the spraying method decreases significantly after about 1 year of use (Staub de Melo et al. 2012;Folli et al. 2015). ...
... Recent research suggests that incorporating translucent particles into concrete as a partial replacement for aggregates can notably enhance the efficiency of photocatalytic materials in the degradation of atmospheric pollutants (Si et al. 2021;Yang et al. 2018). The addition of glass fragments as aggregates in concrete can substantially increase the photocatalytic activity. ...
To mitigate the impact of vehicular emissions on air quality and reduce the concentrations of atmospheric pollutants, this study developed pavement materials with purification functions using TiO 2 as a photocatalyst and construction waste as an aggregate. Polymethyl methacrylate (PMMA) acrylic particles were added to enhance the light transmittance of the concrete, and the volume replacement percentages of PMMA replacing aggregate (sand) were 20%, 40%, 60%, and 80%. The physical, mechanical, and photocatalytic properties of the photocatalytic recycled concrete were characterized through testing the water absorption, drying shrinkage, compressive strength, flexural strength, splitting tensile strength, and degradation efficiency. The results showed that the addition of PMMA increased the water absorption, reduced the drying shrinkage, and decreased the mechanical strength (compressive strength, flexural strength, and splitting tensile strength) of the photocatalytic recycled concrete. Notably, PMMA significantly improved the photocatalytic efficiency by increasing the light transmit-tance, but the promotion effect was weakened when the PMMA replacement percentages exceeded 60%. When the PMMA replacement percentages ranged from 20% to 40%, the photocatalytic recycled concrete maintained good mechanical strength and photocatalytic efficiency. This study presents an effective approach for improving the catalytic efficiency of photocatalytic recycled concrete while concurrently enhancing the utilization rate of construction waste. Practical Applications: The photocatalytic recycled concrete developed in this study has significant potential in practical applications, especially in urban environments. It can serve as a material for roads, sidewalks, and building surfaces. Due to its air purification function, it can break down harmful pollutants in the atmosphere, such as nitrogen oxides and volatile organic compounds, thereby aiding in the improvement of urban air quality. In addition, the use of construction waste as aggregate promotes the recycling of construction waste and reduces dependence on natural resources.
... The question of durability was mainly assessed by quantifying changes in the performance of the photocatalytic coating over time, the performance evaluated being either the self-cleaning capacity (water contact angle) or the air depollution property (degradation of a pollutant) [55][56][57]. Performance loss can be reversible, as in the case of nitrate species or dirt build-up on the surface which can be washed away by rain [58], or irreversible, as in the case of abrasive wear, weathering, or other mechanisms (carbonation of cementitious materials, destruction of polymer binder) [32,59]. The adherence of the photocatalytic coating to the surface is a crucial parameter, especially for asphalt surface applications where abrasive wear is expected in real life due to road traffic. ...
In urban environments, various pollutants generated by road traffic, human, and industrial activities degrade outdoor and indoor air quality. Among these pollutants, nitrogen oxides (NOx) are subject to air quality regulations designed to protect human health and the environment. It is therefore crucial to keep their concentration as low as possible. Advanced oxidation processes are a practical choice for the degradation of NOx; among them, heterogeneous photocatalysis has proven to be a viable route. However, while the efficiency of this process has been widely demonstrated on a laboratory scale, it is still the subject of debate for real-life applications. The purpose of this study was to present a new field experiment on the application of a photocatalytic coating to outdoor walls. Air quality monitoring stations were used to evaluate the NOx concentration reduction instead of the chemiluminescent analyzer, in order to increase the number of sampling points. Statistical analysis was carried out to interpret the results. Density probability functions were plotted and showed a positive impact of the coating, leading to lower NOx concentrations. This work was completed by a laboratory-scale assessment of the coating’s durability using abrasion, QUV, and immersion/drying tests. The air depollution capacity of the chosen coating was significantly reduced after QUV testing.
... These techniques may pertain to the chemical, physical or the biological realms. Strategically, these NGHGET could be considered at Phase B. From the chemical realms, available techniques include the utilization of photocatalytic concrete [15] and the natural carbonation phenomenon [16]. From the physical realm, electrical systems can be devised to draw GHG into porous disposable absorbing films. ...
With escalating adverse effects, climate change is, presently, a critical global issue. The primary agent is the atmospheric high level of carbon dioxide and other pollutants. Concrete significantly contributes to greenhouse gas emissions. Green building is, therefore, a professional responsibility. This analysis briefly proposes various possibilities for reverting to green concrete in construction, advising strategies and solutions implementable at the several life cycle phases of the construction material. Multi-faceted sustainable aspects would pertain to eco-friendly extraction and manufacturing processes, thermal energy-efficient layout, scrubbing of pollutants, and recyclability. In particular, the study sheds light on an important experimental possibility of symbiosing the inert building material with the biological realm: the Living Concrete. At Politecnico Di Milano – Department of Architecture, Built Environment & Construction Engineering, we, first, realized a symbiotic concrete tile with macro-algae Ulva lactuca; then, we developed the experiment to conceive a novel “living concrete” construction finish material designed to absorb/scrub carbon dioxide from the atmosphere. This material consists of concrete blocks with Chlorella vulgaris cultivated on their surface. C. vulgaris is common microalgae with photosynthetic activity. This new photosynthetic concrete finish material was further developed and realized at the University of Verona – Department of Biotechnology with the help of expert professors. Researching effective negative greenhouse gas emissions techniques (NGHGET) from the chemical, physical and/or biological realm presents a valid approach to address and solve climate change problem.
... high-strength concrete [13][14][15], fiber reinforced concrete [16,17], self-compacting concrete [18,19], self-prestressing concrete [18,20,21], etc. A separate group contains photocatalytically active cement systems, which acquire a number of positive properties during light irradiation, including the ability to decompose atmospheric pollutants, to self-clean the material surface, etc. [22][23][24][25][26][27]. ...
... К отдельной группе относят фотокаталитически активные цементные системы, которые в процессе облучения светом приобретают ряд положительных свойств, включая способность к разложению загрязнителей атмосферного воздуха, самоочищению поверхности материала и др. [22][23][24][25][26][27]. ...
Introduction. Currently one of the focus areas for the development of construction material science is the creation of self-cleaning concretes characterized by polydisperse multicomponent composition with the presence of nanoscale photocatalytic additives, primarily based on TiO2. These photoactive modifiers give the material a number of positive properties, including the ability to decompose atmospheric pollutants, to self-clean the surface, etc. The promising method for improving the functional characteristics of titanium oxide photocatalysts is the creation of nanostructured systems with ‘core (substrate) – shell (photocatalyst)’ architecture. Previous research results show that the final efficiency of the synthesized composite photocatalytic modifiers largely depends on the level of substrate reactivity in the cement system. The purpose of this study is to investigate the impact of three types of siliceous rocks (diatomite, trepel, and opoka) on cement stone formation processes and to identify the most effective raw materials for use as photocatalytic carriers in self-cleaning concrete compositions. Methods and materials. The methods of Kozeny-Karman, laser diffraction and X-ray fluorescence spectrometry were used to determine the specific surface area and parameters of granulometric and chemical compositions of silicite samples. The phase composition of siliceous rocks and modified cement systems was studied by X-ray powder diffractometry. Results and discussion. The main parameters of granulometric composition of diatomite, trepel and opoka were determined. The predominance of reactive modifications of free silica (47.6–78.0 wt. %), represented by amorphous opal-A or cryptocrystalline OCT-phase (opal-CT), were revealed in the structure of silicites. It was found that increasing the dosages of silica-containing additives from 0 to 10 % resulted in decreased by 10–27 % in the quantity of portlandite in the phase composition of cement stone aged 28 days, while the content of high-strength low-basic calcium hydrosilicates (C–S–H (I)) increased by 11–27 %. Conclusions. The chemical and mineralogical composition peculiarities of silicites, as well as the nature of the impact of silica-containing modifiers on the structure formation processes of cement systems, determine the prospects of using opal-cristobalite rocks as dispersed photocatalyst carriers for self-cleaning concrete.
... Another usage that has been attracting attention is in decontaminating effluents that contain bacteria [9], viruses [10], and other microorganisms [11]. The number of self-cleaning structures based on photocatalysis is also increasing [12]. ...
Materials based on iron oxide were prepared via a closed system solution combustion synthesis (IOP), evaluating the effect of adding mango seed husk (T), peel (C), and a mixture of the portions (M) on the material properties obtained (IOT, IOC, and IOM, respectively). The structural (XRD, Mössbauer), morphological (SEM and TEM), optical (UV-VIS diffuse reflectance), textural (BET), and magnetic (VSM) properties of the materials obtained were evaluated. Different phase compositions (hematite, magnetite, and maghemite) were identified in the structure of the materials. Adding mango residue favored the formation of magnetite with superparamagnetic particles in the IOC sample. The solids were evaluated in the methylene blue photocatalysis at different concentrations, observing different effects on the discoloration rate. The IOP sample performed better at the lowest concentration (50 mg L⁻¹) of the dye, with 98% discoloration after 90 min and a specific speed of 44.7 × 10⁻³ min⁻¹, which can be explained by the heterojunction effect, making electronic recombination harder and increasing the quantum yield of the photocatalyst. At 70 mg L⁻¹ concentration, the best catalyst was the IOM with 82% discoloration and a specific speed of 15.8 × 10⁻³ min⁻¹, explained by the increase in the specific area due to the insertion of biomass, which improved adsorptive capacity, maintaining the observed heterojunction effects. Under sunlight, the best composite was IOC, with 90.5% discoloration and activity of 29.8 × 10⁻³ min⁻¹, justified by combining favorable textural and optical properties.
Graphical Abstract
... On the other hand, during the preparation of the coating mortars, the synthesized and commercial TiO2 nanoparticles were initially dispersed in water, and this water with the nanoparticles was used as the mixing water. Therefore, part of this water was absorbed directly by the limestone aggregates (considered to have high absorption) [8,36], suggesting that some nanoparticles may be distributed directly in the limestone aggregates, and due to their hydrophilic nature and photocatalytic activity they can react with the water molecules or organic components [18,37,38]. When oxidant radicals (•OH) are generated, a series of chemical reactions are triggered, which cause the bonds of the dye molecules to separate until the entire contaminant is mineralized; oxygen radicals (•O 2− ) also contribute to the elimination of contaminants [15]. ...
... On the other hand, during the preparation of the coating mortars, the synthesized and commercial TiO 2 nanoparticles were initially dispersed in water, and this water with the nanoparticles was used as the mixing water. Therefore, part of this water was absorbed directly by the limestone aggregates (considered to have high absorption) [8,36], suggesting that some nanoparticles may be distributed directly in the limestone aggregates, and due to their hydrophilic nature and photocatalytic activity they can react with the water molecules or organic components [18,37,38]. When oxidant radicals (•OH) are generated, a series of chemical reactions are triggered, which cause the bonds of the dye molecules to separate until the entire contaminant is mineralized; oxygen radicals (•O 2− ) also contribute to the elimination of contaminants [15]. ...
In this study, the photocatalytic activity of coating mortars with synthetized and commercial TiO2 nanoparticles added has been evaluated at 2, 3 and 5% by weight of cement by calculating the degradation efficiency of methyl orange and red wine dyes exposed to both visible-light and UV radiation; also, the self-cleaning effect of coatings exposed to weather conditions (warm sub-humid climate) was assessed. TiO2 nanoparticles were synthesized via the sol–gel method to a low synthesis temperature and characterized via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results show synthesized TiO2 particles in anatase phase with a crystallite size of 14.69 nm, and hemispherical particles with sizes of submicron order. The addition percentage with the best performance in the coating mortars was 3%, with both commercial and synthesized TiO2; however, coating mortars with synthesized TiO2 exhibited the highest degradation efficiency for both dyes when they were exposed to visible light, while mortars with commercial TiO2 exhibited the highest degradation efficiency when exposed to UV radiation. In addition, in coating mortars with synthesized TiO2, the self-cleaning effect was evident from the beginning of exposure to weather, reaching the largest dye-free surface at the end of exposure. The compressive strength increased significantly in mortars with TiO2 addition.
... Photocatalytic cementitious composites prepared via Method I exhibit a lower exposure efficiency of TiO 2 nanoparticles but boast a more durable photocatalytic performance due to the strong bonding between TiO 2 nanoparticles and the surrounding cement hydrates. Photocatalytic cementitious composites prepared by Method II exhibit high early-stage photocatalytic performance (attributable to efficient exposure) but suffer a rapid decline during the engineering service due to weak adhesion between photocatalysts and the matrix surface [4][5][6][7]. ...
... Another usage that has been attracting attention is in the decontamination of effluents that contain bacteria [9], viruses [10] and other microorganisms [11]. The number of self-cleaning structures based on photocatalysis is also increasing [12]. ...
Materials based on iron oxide were prepared via closed system solution combustion synthesis (IOP), evaluating the effect of the addition of mango seed Husk (T) peel (C) and mixture of the portions (M) on the material properties obtained (IOT, IOC and IOM, respectively). The structural (XRD, Mössbauer), morphological (SEM and TEM), optical (UV-VIS diffuse reflectance), textural (BET) and magnetic (VSM) properties of the materials obtained were evaluated. Different phase compositions (hematite, magnetite and maghemite) were identified in the structure of the materials. The addition of mango residue favored the formation of magnetite with superparamagnetic particles in the IOC sample. The solids were evaluated in the methylene blue photocatalysis at different concentrations, observing different effects on the discoloration rate: the IOP sample presented a better performance at the lowest concentration (50 mg L-1) of the dye, with 98% discoloration after 90 minutes and a specific speed of 44.7 x 10-3 min-1, which can be explained by the heterojunction effect, which makes electronic recombination harder, increasing the quantum yield of the photocatalyst. At the concentration of 70 mg L-1, the best catalyst was the IOM with 82% of discoloration and specific speed of 15.8 x 10-3 min-1, which can be explained by the increase in the specific area due to the insertion of biomass, which improved adsorptive capacity, maintaining the observed heterojunction effects. Under Sunlight, the best composite was IOC, with 90.5% discoloration and activity of 29.8 x 10-3 min-1, justified by the combination of favorable textural and optical properties.
