Search Results (53)

This study elucidates the photocatalytic NOx abatement efficacy of eco-efficient mortars incorporating construction waste-derived aggregates functionalized with nano-TiO₂. The research findings demonstrate a positive correlation between NOx abatement efficiency and nano-TiO₂ substitution ratio, with recycled glass sand (RG)-based panels exhibiting superior performance compared to standard sand and recycled clay brick sand (RCBS)-based counterparts. The employment of ultrasonic dispersion as a nano-TiO₂ incorporation method yields enhanced abatement efficiency relative to direct mixing, attributable to improved photocatalyst dispersion and surface area accessibility. The loading capacity of nano-TiO₂ on recycled aggregates is observed to be positively influenced by the concentration of nano-TiO₂ solution, with recycled clay brick sand demonstrating the highest loading capacity. RG-RCBS panels are shown to exhibit higher NOx abatement efficiency than standard sand (SS)-RCBS panels, with an optimal substitution ratio of 40% glass sand identified for maximizing abatement efficacy in RG-RCBS systems. A decline in NOx abatement efficiency is observed with increasing NOx flow rate and concentration, attributable to reduced pollutant residence time and excess pollutant load exceeding the panels’ processing capacity. Prolonged curing time also results in diminished abatement efficiency, due to microstructural alterations within the mortar matrix and the accumulation of photocatalytic reaction byproducts. Collectively, these findings underscore the potential of recycled aggregate-based mortars, in conjunction with nano-TiO₂, as a viable eco-efficient strategy for NOx abatement, highlighting the critical influence of material selection, photocatalyst loading, and operational parameters on system performance. Full article

Nano-TiO₂-modified mortars are fabricated by introducing TiO₂ nanoparticles to the conventional mortar mix with designed mixing and curing procedures. It was found that additional TiO₂ nanoparticles can accelerate hydration and improve the air void distribution in the mortar matrix. The experiments also showed that 0.5 wt.% and 1 wt.% TiO₂-modified mortar has a comparable mechanical strength to traditional cement mortar. The abrasion resistance is improved with nanoparticles at 0.5 wt.% TiO₂ concentration. The photocatalytic performance of photocatalytic mortar was confirmed by a methylene blue decomposition test. Finally, a multi-physics computational model was constructed to assess the effects of photocatalytic mortar coated on building in air quality improvements in the neighboring area. The benefits are affected by different nano-TiO₂ concentrations, as well as wind conditions in the neighborhood. Overall, this study shows that properly designed nano-TiO₂-modified mortar is promising to achieve multifunctional performance in terms of mechanical strength and durability as well as autogenous self-cleaning of surrounding environment. Full article

This study investigates the relationship between surface properties and microstructural characteristics of photocatalytic composites and their impact on air purification efficiency. High-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and mercury intrusion porosimetry (MIP) were employed to analyze photocatalyst distribution and pore structure quantitatively. The findings demonstrated a strong correlation between TiO₂ coverage on the photoactive surface and NO removal rates and between pore structure characteristics and NO₂ generation rates. Two predictive models were developed to link NOx removal rates with photocatalytic cementitious mortars’ surface and structural properties. A stepwise regression approach produced a second-degree polynomial model with an adjusted R² of 0.98 and a Mean Absolute Percentage Error (MAPE) of 8.34%, indicating high predictive accuracy. The results underscore the critical role of uniform photocatalyst distribution and optimized pore structure in enhancing NOx removal efficiency while promoting the generation of desirable products (NO₃⁻) and minimizing the formation of undesirable byproducts (NO₂). Full article

This study investigated the influence of the composition of photocatalytic dispersions made with second-generation nano-TiO₂ on the air purification performance of photocatalytic cementitious composites. Nine mortar series were prepared, incorporating photocatalytic dispersions of variable content of nano-TiO₂, dispersing agent (superplasticizer), and hydrophobic admixture. The total mass content of nano-TiO₂ in investigated mortars was kept at the same level. For investigated composites, photocatalytic removal of NOx was evaluated under simulated laboratory conditions mimicking polish autumn/winter irradiation conditions. The results indicate that within the tested range of variability, the dispersion composition significantly influenced the granulation of the dispersed nano-TiO₂ particles, which in turn affected the air purification performance of the composites. A predictive model was developed to account for environmental factors potentially influencing photocatalytic performance in urban environments. The model estimated that, depending on environmental conditions and photocatalytic dispersion composition, the composite’s photocatalytic layer could remove up to 1.067 g/m² of NO₂ per year in favorable environmental conditions. Photocatalytic cementitious composites can act as environmentally beneficial composites, contributing to carbon-negative construction practices and improving urban air quality. This highlights the dual benefits of offsetting embedded carbon emissions and enhancing air purification efficiency in sustainable urban infrastructure. Full article

This study focused on the preparation and investigation of g-C₃N₄/TiO₂ photocatalysts using different TiO₂ morphologies (anatase nanoparticles (TPs), poorly crystalline nanotubes (aTTs), and well-crystalline anatase nanorods (TRs)) and self-synthesized g-C₃N₄ (CN). The synthesis of the g-C₃N₄/TiO₂ composites was carried out using a mortar mixing technique and a g-C₃N₄ to TiO₂ weight ratio of 1:1. In addition, the g-C₃N₄/TiO₂ composites were annealed in a muffle furnace at 350 °C for 2 h in air. The successful formation of a g-C₃N₄/TiO₂ composite with a mesoporous structure was confirmed using the results of XRD, N2 physisorption, and FTIR analyses, while the results of microscopic analysis techniques confirmed the preservation of TiO₂ morphology in all g-C₃N₄/TiO₂ composites investigated. UV-Vis DR measurements showed that the investigated g-C₃N₄/TiO₂ composites exhibited visible-light absorption due to the presence of CN. The results of solid-state photoluminescence and electrochemical impedance spectroscopy showed that the composites exhibited a lower charge recombination compared to pure TiO₂ and CN. For example, the charge transfer resistance (RCT) of the CNTR/2 composite of TR and CN calcined in air for 2 h was significantly reduced to 0.4 MΩ, compared to 0.9 MΩ for pure TR and 1.0 MΩ for pure CN. The CNTR/2 composite showed the highest photocatalytic performance of the materials tested, achieving 30.3% degradation and 25.4% mineralization of bisphenol A (BPA) dissolved in water under visible-light illumination. In comparison, the pure TiO₂ and CN components achieved significantly lower BPA degradation rates (between 2.4 and 11.4%) and mineralization levels (between 0.6 and 7.8%). This was due to (i) the presence of Ti³⁺ and O-vacancies in the TR, (ii) enhanced heterojunction formation, and (iii) charge transfer dynamics enabled by a dual mixed type-II/Z scheme mechanism. Full article

This study explores the development and performance of photocatalytic cementitious composites modified with nano-TiO₂ to address urban air quality and sustainability challenges. Nine mortar series were prepared, incorporating binders with varying carbon footprints and mass contents across different series. The interplay between the fundamental (abrasion resistance) and functional (air purification efficiency) properties of the composites’ surfaces and interfaces was investigated. The photocatalytic removal of airborne pollutants, specifically nitrogen oxides (NOx) and ozone (O₃), was evaluated under simulated environmental conditions. The variations in binder composition influenced the composites’ overall initial carbon footprint and air purification efficiency. The assessment revealed a possible net decrease in carbon emissions over the life cycle of the composite due to the removal of ozone (greenhouse gas) and its precursor—NOx, highlighting the potential of photocatalytic cementitious composites for dual environmental benefits in an urban environment, emphasizing the critical role of surface and interface engineering in achieving carbon-negative composites. Full article

This research investigated the properties of photocatalytic cementitious composites, including their air-purification efficiency. A method of characterizing the removal of airborne pollutants (nitrogen oxides), simulating the actual NO_x concentration and irradiation conditions in Warsaw, Poland, in the autumn/winter season was established. The study analyzed the impact of changes in the composition of cement mortars—partial substitution of the binder with mineral fillers—on the properties of the external photoactive surface of the composite. The designed experimental plan included both quantitative and qualitative variables (type and amount of fillers used). It was found that the photocatalytic performance of the composite was correlated with its pore total content and pore size distribution—the higher the content of mineral fillers, the lower the porosity and the less effective its photocatalytic properties. The selectivity of the photocatalytic NO_x reactions also deteriorated as the content of the mineral fillers increased. The study confirmed the validity of increasing the binder content in cementitious composites to enhance their photocatalytic performance. Full article

The purpose of this research was to study the influence of multifunctional anatase–silica photocatalytic materials (ASPMs) with various photocatalytic and pozzolanic activities on the properties of white portland cement and fine-grained concrete. ASPMs were synthesized by a sol–gel method, during which the levels of photocatalytic and pozzolanic activity were regulated by a certain amount of solvent. ASPMb, obtained with the use of a smaller amount of solvent, was characterized by increased pozzolanic activity due to the lower degree of coating of the surface of diatomite particles with titanium dioxide and the higher content of an opal–cristobalite–tridymite-phase and Bronsted acid sites. They promoted the reaction of diatomite with portlandite of cement stone and allowed significant decreases in the strength of cement–sand mortar to be avoided when replacing 15% of the cement with ASPMs. This allowed self-cleaning fine-grained concrete to be produced, which, after forced carbonization, simulating the natural aging of the product during operation, retained the ability of self-cleaning without changes. ASPMc, produced with the use of a larger amount of solvent with a more uniform distribution of titanium dioxide on the surface of diatomite, allowed fine-grained concrete with a high self-cleaning ability to be obtained, but with a lesser manifestation of the pozzolanic effect. Full article

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. Full article

Building envelopes coated with TiO₂-based mortars benefit from depolluting, antibiological and self-cleaning effects. Therefore, photocatalytic renders are allies in the quest for sustainability in the built environment, potentially combatting atmospheric pollution, enhancing durability and reducing maintenance needs. Surface finishing characteristics of the renders influence their photocatalytic efficiency and esthetic and functional properties. In this context, this study reviews the existing literature, focusing on proven surface-affecting parameters, the surface and color of TiO₂-based mortars, to explore their impacts on photoactive behavior. The incorporation of TiO₂ within an additional surface layer and its mixture into the mortar in bulk were observed for surface roughness. Mainly the addition of TiO₂ during casting was identified in colored mortars. Generally, a moderate surface roughness led to better photoactivity; microroughness affected self-cleaning by facilitating dirt deposition. The interaction between the surface roughness and the photocatalytic layer affected the water contact angle, regarding superhydrophilicity or superhydrophobicity. The photoactivity of colored mortars with TiO₂ depended on the color and amount of the added pigments, which influenced electron–hole recombination, physically occupied active sites or, on the other hand, led to a higher formation of reactive radicals. Surface finishing can thus be designed to enhance the photoactivity of TiO₂-based mortars, which is fundamental for current climate concerns and emphasizes the need for life cycle assessments and environmental protection. Full article

Self-cleaning products are commercially available to protect surfaces against soiling and avoid the high consumption of energy and chemical detergents necessary for cleaning. They are based on semiconductor oxides, mostly titanium dioxide (TiO₂), which induce photocatalytic oxidation activity and superhydrophilicity. Therefore, we present an experimental procedure at a lab scale to assess the self-cleaning ability of various photocatalytic coatings (five TiO₂-based commercial products and one lab-grade zinc oxide (ZnO) product) applied to mortar surfaces. The samples were artificially stained with three types of soiling: Congo red dye, diesel soot, and motor oil. They were exposed to the environmental cycle of UV illumination and water flow for two weeks and the changes in stain colors were first assessed with visual inspection. Then, spectrophotometry measurements were conducted before and after the self-cleaning experiment to calculate the color differences for each stain in the CIELab color space data. In addition, the coatings were characterized via X-ray diffraction analyses and water contact angle measurements. Results highlighted color changes for each stain and higher wettability (induced by OH radicals) of the coated surfaces, which favored surface washing and thus stain removal. Light also had a positive effect on the attenuation of the stains, particularly for the Congo red dye. Full article

The application of nano-TiO₂ as a photocatalytic agent in buildings’ internal surfaces has recently attracted attention to mitigate microorganism growth, soiling, and contamination in indoor environments. This work aimed at comparing the Rhodamine B (RhB) dye degradation efficiency of three different mortar compositions subjected to simulated internal radiation, in which nano-TiO₂ (10 wt% of binder mass) was dispersed by ultrasonic and mechanical methods. Mortar specimens were produced with white Portland cement, hydrated lime, sand, and water in different volume proportions of 1:1:6 (cement:lime:sand), 1:3 (cement:sand), and 1:4 (cement:sand). The first stage of the research evaluated samples exposed to the natural outdoor environment and proved the efficiency of specimens’ photoactivity when covered by a glass layer. The second and principal phase of the study simulated indoor conditions in glazed buildings through artificial weathering in which the composition of 1:1:6 was mechanically dispersed and exhibited the highest global color change (ΔE) values for RhB staining. The main finding of the study was that the mortars exposed to simulated indoor conditions presented high ΔE grades, classified as easily perceived by the human eye. This demonstrates the photocatalytic efficiency in an internal building environment that receives radiation through a glass surface. Full article

In this research, we aimed to design an eco-efficient composite based on alkali-activated materials (AAMs) with self-cleaning properties for sustainable construction. Significant emphasis was placed on determining the role of the type of precursor, the amount of sodium silicate, and the addition of titanium dioxide on the rheological and mechanical properties of AAMs. An important aspect of the research was the modification of AAM with titanium dioxide to obtain the self-cleaning properties. Titanium dioxide, thanks to its photocatalytic properties, enables the reduction of organic pollutants and nitrogen oxides in the urban atmosphere and promotes the cleaning of material surfaces. Blast furnace slag (BFS) was used as the source material, which was then substituted in subsequent formulations with metakaolinite at 50% and fly ash and zeolite at 30%. The best-activated AAMs, in which blast furnace slag and its mixture with metakaolinite were used as precursors, achieved compressive strengths of 50 MPa. BFS mixtures with pozzolans were more difficult to polymerize, although their final strengths were still relatively high, in the range of 33–37 MPa. Adding titanium dioxide (T) improved the final strengths and slightly lowered the heat of hydration and spreading of the AAM mortars. The best self-cleaning properties were achieved with composites that comprised a mixture of blast furnace slag, fly ash, and 2% titanium dioxide. Full article

A facile and cost-effective approach assisted by ball milling (BM) of commercial titanium dioxide (TiO₂), has been utilized to develop cheaper and efficient construction materials. At least three of the commercial and cheaper TiO₂ samples (BA01-01, BA01-01+ and R996, designated as A1, A4 and R1, respectively) were selected and subjected to BM treatment to enhance their photocatalytic efficiencies, if possible. It was noted, that the samples A1, A4 and R1 were typical composites of TiO₂ and calcium carbonate (CaCO₃) and contained varying proportions of anatase, and rutile phases of TiO₂ and CaCO₃. Two of the highly efficient commercial TiO₂ samples, Degussa P25 (simply designated as P25) and ST01 (Ishihara Ind.) were selected for making benchmark comparisons of photocatalytic efficiencies. The BM treated TiO₂ samples (designated as TiO₂-BM with respect to A1, A4 and R1) were evaluated for photocatalytic efficiencies both in both aqueous (methylene blue (MB)) and gaseous (NO_x) photodegradation reactions. Based on detailed comparative investigations, it was observed that A1-BM photocatalyst exhibited superior photocatalytic performances over A4-BM and R1-BM, towards both MB and NO_x photodegradation reactions. The difference of NO_x photodegradation efficiency between the mortar mixed with A1-BM and that mixed with ST01, and P-25 at 15% were 16.6%, and 32.4%, respectively. Even though the mortar mixed with A1-BM at 15% composition exhibited a slightly lower NO_x photodegradation efficiency as compared to mortar mixed with the expensive ST01 and P-25 photocatalysts, the present work promises an economic application in the eco-friendly construction materials for air purification considering the far lower cost of A1. The reasons for the superior performance of A1-BM were deduced through characterization of optical properties, surface characteristics, phase composition, morphology, microstructure and particle size distribution between pristine and BM treated A1 using characterization techniques such as diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, field emission scanning electron microscopy and particle size analysis. Full article

The effect of titanium dioxide (TiO₂) on the mechanical properties of cement slurries including their benefits on air purification and abatement of pollutants is not well documented. Cementitious-based slurries are typically applied in thin layers as decorative coatings for existing facades, protection against an ingress of aggressive ions, or rainproof covers to minimize water penetration. Different parameters including the TiO₂ concentration, dispersion time during batching, and applied thickness on top of existing mortar blocks are investigated in this paper. Tested properties included the flow, colorimetry, compressive/flexural strengths, bond to existing substrates, water absorption, and photocatalytic activity evaluated using an ISO 22197-1:2007 reactor. The results showed that the mechanical properties remarkably improved with TiO₂ additions, up to 8% of the cement mass. This was attributed to two concomitant phenomena including a micro-filler effect that enhances the packing density and nucleation sites to promote strength development. The removal of nitrogen oxides from the atmosphere reached 92% when the TiO₂ was added at a rate of 5% of the cement mass. Such data can be of particular interest to consultants and environmental activists searching for innovative materials capable of maintaining better ambient air quality in urban and modern cities. Full article