Role of photocatalytic cementitious materials in the reduction of air pollution

Abstract

Severe environmental pollution around the world has brought attention to the impending need for innovation and environmentally friendly technological processes. Increased air pollution due to urbanization has resulted in health hazards associated with climate change and accelerated resource degradation are directing towards sustainable development Oxides of nitrogen (NO_x) are one of the major air pollutants which are a group of highly reactive gases of nitric oxide (NO) and nitrogen dioxide (NO₂). The formation of tropospheric ozone, urban smog, acid rain, etc. is several detrimental impacts of NO_x. A possible solution for the remediation of these reactive gases may be heterogeneous photocatalysis using photocatalysts such as titanium dioxide (TiO₂) which can adsorb and oxidize organic and inorganic particles in the air, such as NO_x and VOCs in the presence of ultraviolet light (sunlight) [1]-[2].

Fig.1. Mechanism of Photocatalytic Degradation

Photocatalysis is a process that involves the action of photocatalytic semiconducting metal oxides which get activated under UV radiation. Numerous semiconductors have exhibited photocatalytic degradation of the contaminants. However, TiO₂ plays a lead role in the degradation of air pollutants. Photocatalytic degradation is promising for cities where ground-level pollutant concentrations are very high. Self-cleaning and air-purifying coatings with a super-hydrophilic photocatalyst such as TiO₂ on buildings can bring down the NO_x concentration in the surrounding air to an extent. In addition, the incorporation of TiO₂ in the form of nanoparticles into cementitious materials will enhance their durability microstructure, and mechanical properties [3].  

This paper provides an overview of the photocatalytic degradation mechanism as indicated in figure 1, different methods of incorporating nano photocatalysts such as nano TiO₂, its effects on the fresh and hardened properties, mechanical properties, and durability of the cementitious composites.