Photocatalytic activity of titanium dioxide nanoparticle coatings applied on autoclaved aerated concrete: Effect of weathering on coating physical characteristics and gaseous toluene removal

Abstract

Autoclaved aerated concrete has been coated by TiO2 nanoparticles through a dip-coating (DC) and a novel vacuum saturation (VS) method to investigate the weathering resistance and gaseous toluene removal potential of both coating types. The effect of intensive weathering – corresponding to a period of about 25 years – on the coating characteristics was studied in terms of TiO2 content, coating thickness and color changes. Toluene removal was investigated in a lab-scale flow-through photoreactor at 24°C and 52% relative humidity, and results obtained immediately after application of the coatings and after two weathering stages were compared. Weathering of the DC and VS coated samples resulted into a decrease of the coating layer thickness of more than 98%, confirmed by a decline in TiO2 content by more than 99% and 93%, respectively. Surprisingly, toluene removal efficiencies before and after weathering kept constant at about 95% for both coating types, corresponding to an elimination rate of 60–70mg/(m2h) at an initial toluene concentration of 15ppmv and a gas residence time of 3min. Increasing the toluene load by applying higher toluene inlet concentrations (up to 35ppmv) and lower gas residence times (1min) did decrease the toluene removal efficiency to 32–41%, but elimination rates increased up to 214mg/(m2h), being a factor of 1.6–4.5 times higher than reported in recent work.