Applications of Titanium Dioxide Photocatalysis to Construction Materials

State-of-the-Art Report of the RILEM Technical Committee 194-TDP

herausgegeben von: Yoshihiko Ohama, Dionys Van Gemert

Verlag: Springer Netherlands

Buchreihe : RILEM State-of-the-Art Reports

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

Titanium dioxide photocatalysis is based on the semiconducting nature of its anatase crystal type. Construction materials with titanium photocatalyst show performances of air purification, self-cleaning, water purification, antibacterial action.

This book describes principles of titanium dioxide photocatalysis, its applications to cementitious and noncementitious materials, as well as an overview of standardization of testing methods.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

A photocatalyst is a semiconducting substance which can be chemically activated by light radiation that results in oxidation-reduction (redox) reaction, i.e., it has a photocatalysis action or photoactivity. As illustrated in Fig. 1.1 [16, p. 147; 24, p. 10], photocatalysis is similar to the photosynthesis in plants in the mechanism, in which chlorophyl acts as a catalyst to produce oxygen from carbon dioxide and water. Chlorophyl is a very powerful photocatalyst. The photocatalyst in the photocatalysis process corresponds to the chlorophyl in the photosynthesis process.

Yoshihiko Ohama, Dionys Van Gemert

Chapter 2. Principles of TiO2 Photocatalysis

Abstract

A substance can be thought to be a catalyst when it accelerates a chemical reaction without being consumed as a reactant; that is to say, it appears in the rate expression describing a thermal reaction without appearing in the stoichiometric equation [49]. A catalyst is a compound that lowers the free activation enthalpy of the reaction. Then, photocatalysis can be defined as the acceleration of a photoreaction by the presence of a catalyst [38, pp. 362–375]. This definition, as pointed out in [29, pp. 1–8], includes photosensitization, a process by which a photochemical alteration occurs in one molecular entity as a result of initial absorption of radiation by another molecular entity called the photosensitizer [13], but it excludes the photoacceleration of a stoichiometric thermal reaction irrespective of whether it occurs in homogeneous solution or at the surface of an illuminated electrode. Otherwise, any photoreaction would be catalytic [29, pp. 1–8]. Depending on the specific photoreaction, the catalyst may accelerate the photoreaction by interaction with the substrate in its ground or excited state and/or with a primary photoproduct.

Marta Castellote, Nicklas Bengtsson

Chapter 3. Application of TiO2 Photocatalysis to Cementitious Materials for Self-Cleaning Purposes

Abstract

Cementitious materials, especially those exposed to outdoor conditions, are directly and continuously exposed to many atmospheric pollutants, (organic, inorganic and particulate matter), microorganisms (e.g., algae, fungi, cyanobacteria) and different weather conditions. As a result, they have an accelerated deterioration process which can produce in many cases important changes in the materials properties, among them aesthetic properties. Colour, for example, has to give a pleasant appearance that should give to the public an adequate perception of the quality and maintenance of buildings or structures. However, serious colour changes are produced on the buildings and structures due to the mineral composite nature of cementitious materials. The nature causes relatively high porosity and roughness, which enable the deposition of coloured organic pollutants or particulate matter and partially facilitate biological growth.

Anibal Maury Ramirez, Nele De Belie

Chapter 4. Application of Antibacterial and Self-Cleaning Effects to Noncementitious Construction Materials

Abstract

Recently, photocatalyst coating technology enabled to produce construction materials having advanced functions such as sterilizing, deodorizing and self-cleaning properties.

Yoshimitsu Saeki

Chapter 5. Applications of TiO2 Photocatalysis for Air Purification

Abstract

A system consisting of TiO₂ and cement has recently been studied within the framework of a strategy for alleviating environmental pollution through the use of construction materials containing photocatalysts. This technology for the photocatalytic degradation of organic pollutants is aimed at maintaining the aesthetic characteristics of concrete structures, particularly those based on white cement. The main reason for the discoloration of cementitious materials is the accumulation of coloured organic compounds on their surfaces (see also Sect. 3.2). Suitable amounts of TiO₂ have been introduced into cement mixes to render the surfaces of the resulting structures photocatalytically active. In order to verify the photocatalysis, experiments focusing on the oxidation of several kinds of aromatic organic compounds have been carried out. For instance, white cement disks have been impregnated with a phenanthroquinone solution (0.1 mg/cm²), yielding homogeneously yellow surfaces. Accelerated irradiation tests were then performed with a solar simulator (100 h of irradiation, corresponding to 1 year of sunlight). A rapid restoration of the clean surface was obtained.

Anne Beeldens, Luigi Cassar, Yoshihiko Murata

Chapter 6. Standardization of Testing Methods for Construction Materials with TiO2 Photocatalyst

Abstract

In order to get uniformity for the determination and verification of test results for photocatalytic construction materials, it is essential to define performance-based attributes and test methods. This chapter summarizes the current state-of-the-art on the existing standards, and shows an example for a performance-based procedure which covers the removal of nitric oxides (NO_x).

Kenji Motohashi, Frank Dehn, Yoshihiko Ohama

Chapter 7. Conclusions

Abstract

Since the early applications in 1972 of photocatalysis by titanium dioxide by Fujishima and Honda [15], a rapid progress has taken place. The technology of TiO2 photocatalyst or photocatalysis has become very attractive in the development of construction materials and construction techniques for self-cleaning, air or water purification, and antibacterial functions. No further chemicals have to be used, only sunlight and rainwater. Photocatalyst technology is being applied on ceramic, glass and cementitious surfaces, as well as in paints. Exterior as well as interior applications exploit the benefits of TiO2 photocatalysis. Application of photocatalysis to the envelopes of buildings, road facilities and tunnels reduces air pollution, and thus contributes to an enhanced control of heat island phenomena in densely populated cities or heavy traffic areas.

Yoshihiko Ohama, Dionys Van Gemert

Backmatter

Titel: Applications of Titanium Dioxide Photocatalysis to Construction Materials
herausgegeben von: Yoshihiko Ohama
Dionys Van Gemert
Verlag: Springer Netherlands
Electronic ISBN: 978-94-007-1297-3
Print ISBN: 978-94-007-1296-6
DOI: https://doi.org/10.1007/978-94-007-1297-3