Titanium dioxide coated cementitious materials for air purifying purposes: Preparation, characterization and toluene removal potential

This work presents promising results for air purification by heterogeneous photocatalysis on new titanium dioxide loaded cementitious materials. A set of eight concretes and plasters is enriched with TiO2 photocatalyst by dip-coating and/or sol–gel methods. First, the macro-structural features of the cementitious materials have been studied in terms of porosity and roughness. The first parameter has been determined using mercury intrusion porosimetry or by vacuum saturation, and ranged between 9 and 75%, with the highest values obtained for autoclaved aerated white concrete. Surface roughness, determined by laser profilometry, has been characterized by the Ra factor. This expresses the mean deviation of the profile from the centre line and ranged between 0.7 and 252 μm, with the highest value obtained for conventional grey concrete finished with surface brush. Secondly, the weathering resistance of the TiO2 coatings has been determined by exposing them to different abrasive conditions and by performing SEM-Edax analyses to measure quantitatively the coatingʹs titanium content. Hereby, it is shown that high porosity and roughness are favourable for TiO2 particles retention. Finally, the preliminary air purification potential of both dip-coated and sol–gel coated TiO2 enriched concrete samples has been investigated on lab-scale using toluene as a model pollutant. High removal efficiencies (up to 86%) were obtained with the dip-coated samples, indicating their attractive photocatalytic properties for future application as air purifying building materials.