Measurement of benzene, toluene, ethylbenzene and o-xylene gas phase photodegradation by titanium dioxide dispersed in cementitious materials using a mixed flow reactor

Materials rich in organic and inorganic compounds, such as building materials or paints, represent an excellent substrate for the development of moulds. Several conditions affect mould's growth on cementitious materials, such as nutrient and water availability, temperature, pH and moisture. Microorganisms, and especially moulds, attack these surfaces and contribute to their erosion, thereby reducing the life of the structure itself and negatively affecting human health through inhalation, ingestion and dermal contact with spores. Interventions are based on The European Communities Council Directive 89/106/EEC, that obliges the use of materials, products and building elements that are resistant to fungi and other forms of degradation, and that do not constitute a health risk for users and the environment. This mini-review summarises the current state of problems related to mould growth on cementitious building materials, emphasising new innovative approaches for limiting or contrasting their growth. In particular, the use of nanoparticles and the related nanomaterials as well as the potential use of new "biocides" from natural sources is discussed.

Enhanced photocatalytic degradation of VOCs using Ln 3+–TiO 2 catalysts for indoor air purification

Photoinduced processes governed by light activated TiO2 have been studied in many ways. One of the most active areas is the development of TiO2 photocatalysis technologies on their application for reducing environmental impacts. The immobilization of TiO2 on solid support, such as cementitious materials, greatly enhances its use in practical applications. In this review, a wide range of applications for achieving eco-efficient building using cementitious composite materials containing TiO2 photocatalyst was presented. The basic mechanism of photocatalysis, such as electron excitation, charge transfer process, reactive oxygen species (ROS) generation, and its role to oxidize the pollutant and microorganisms were extensively discussed. Unlike self-cleaning and air purification systems, the study on the antibacterial function of a cement-based surface containing TiO2 is very limited. In photocatalytic cementitious materials, the key element affecting the photocatalytic performance is the accessible active surface area. However, microstructure of cementitious materials changes with age due to hydration and surface carbonation. Hence, surface area reduction and mass transfer limitation become the main drawbacks of incorporating TiO2 in cementitious materials. This review, therefore, provides the state of the art in photocatalytic cement-based composite materials and identifies the areas in which future improvement is needed.

Enhancement effect of TiO2 immobilized on activated carbon filter for the photodegradation of pollutants at typical indoor air level

Evaluation of the influence of environmental conditions on the efficiency of photocatalytic coatings in the degradation of nitrogen oxides (NOx)

Signs of in-situ geochemical interactions at the granite–concrete interface of a radioactive waste disposal

Photocatalytic activity of titanium dioxide modified concrete materials – Influence of utilizing recycled glass cullets as aggregates

Incorporation of TiO2 into cementitious materials is an important technology in the field of photocatalytic pollution mitigation; however, the photocatalytic activity of TiO2 is limited by specific surface area, poor gas diffusion and light transmission performance of cementitious materials. In this study, a novel photocatalytic lightweight aggregate—photocatalytic ceramsite sand (PCS) was synthesized by loading TiO2 on activated porous ceramsite sand (CS) with negative pressure method to solve problems in application of photocatalysts in cementitious materials. Photocatalytic cement material (PCM) was prepared by loading PCS on the surface of cementitious materials, which improved the photocatalytic activity and efficiency of TiO2 in cementitious materials. It was found that the pore structure (pore volume, size distribution and interconnectivity) of ceramsite sand (CS) varies with particle size. The photocatalytic removal rate of benzene on PCS increased significantly through adjusting ceramsite sands in appropriate pore structure and TiO2 at best coating ratio. The photocatalytic activity of PCS slightly decreased but still remained active after incorporated into concrete. 2 μL benzene was degraded completely in 200 min by 5 g 4PCS-1.25~2.35 and 300 min by PCM-5, and was still degraded over 80% in 400 min by PCM-5 after exposure to natural environment for 6 months. The results suggested that the photocatalytic activity of TiO2 in cementitious materials was enhanced by the preparation of PCS and PCM, which could provide more gas diffusion, higher specific surface area, more TiO2 active sites, and prevent TiO2 particles from being influenced by the envelope of cement hydration products and the carbonation of cement.

The esterification of glycerol with oleic acid for the production of glycerol oleates in the presence of methyl ester sulfonate acid as a homogeneous catalyst was studied. The study was carried out experimentally in a batch reactor with reaction time up to 360 minutes and temperature between 100 and 175 °C. The results showed that the yield of the glycerol oleates increased with increasing reaction time and temperature, reaching the highest yield of 82.61%. The kinetic of the glycerol oleates yield was examined, and the calculations showed that the reaction follows a third-order kinetic model, and the activation energy and frequency factor were determined. The obtained reaction kinetics data were invested in modeling and simulating the esterification reaction of glycerol with oleic acid in ideal mixed and plug flow reactors. The simulation results demonstrated that the effect of the temperature on the yield of glycerol oleates in the mixed flow reactor is less than that of the plug flow reactor. The results also indicated that the mixed flow reactor is suitable when the required glycerol oleates yield is less than 63%, while the plug flow reactor is suitable for higher yield values.

Cementitious building materials like Ultra High Performance Concrete (UHPC), Self-Compacting Concrete (SCC) or concrete with low clinker content possess complex rheological properties. Due to high packing densities and the use of various additives and chemical admixtures, a huge range of non-Newtonian flow characteristics from shear-thinning to shear-thickening, visco-elastic material behaviour and structural build-up can appear. For these concretes, transient computational modelling using Computational Fluid Dynamics (CFD) requires a meaningful choice of rheological parameters and the associated boundary conditions. The authors present the rheological analysis of five cementitious pastes with low ( = 0.45) to high ( = 0.58) solid volume fraction . Rheological parameters from rheometric flow protocols are compared with empirical stoppage test results for short and steady (slump flow) and transient flow (L-Box) conditions. Following, numerical simulation with the measured rheological parameters as input parameters is compared to the experimental flow results. CFD analysis using OpenFOAM is performed for the flow in empirical stoppage tests. We found that with increasing non-Newtonian behaviour, deviations between real and simulated flow appear due to insufficient transient flow descriptions and unknown secondary effects. The results provide new insight into computational modelling of complex cementitious building materials and serve as basis for further advanced CFD based modelling and characterization of time-dependent non-Newtonian concrete flow.

Incorporation of titanium dioxide nanoparticles in mortars — Influence of microstructure in the hardened state properties and photocatalytic activity

Improved photocatalytic nitrogen oxides removal using recycled glass-nano-TiO2 composites with NaOH pre-treatment

Preliminary experimental study on the effects of surface-applied photocatalytic products on the durability of reinforced concrete

Low irradiance toluene degradation activity of a cementitious photocatalytic material measured at constant pollutant concentration by a successive approximation method

Integrated gas chromatography for ultrafast analysis of volatile organic compounds in air