Developed photocatalytic semi-flexible pavement for automobile exhaust purification using iron-doped titanium dioxide

Abstract

To develop a green and sustainable photocatalytic semi-flexible pavement (SFP) for automobile exhaust (AE) purification using the iron (Fe)-doped titaniumdioxide (TiO2) loaded in the adsorbable hardened cement paste of SFP, the effects of Fe doping on microstructure and photoabsorption performances of TiO2 were discussed. Also, the catalytic purification efficiency of Fe-doped TiO2 to AE and its influences on pavement performances of SFP were investigated. Test results indicate that the prepared Fe-doped TiO2 is anatase phase. Fe ions are successfully doped into TiO2, improving its catalytic efficiency when exposed to visible light. The grain size of Fe-doped TiO2 is 14–18 nm. The doped Fe ion inhibits the growth of crystalline grain in TiO2. Also, the photoabsorption edge band shows an obvious red shift from ultraviolet to visible light region. The band gap of TiO2 is obviously decreased by the Fe doping, and the visible light absorbance of TiO2 is increased, improving its utilization efficiency of solar irradiation. Further, the Fe-doped TiO2 shows higher purification efficiency to HC and NOx, following the pseudo-first-order kinetics reaction model. The purification reaction of HC occurs to produce CO2 and H2O. Additionally, the acidulous NOx is easily adsorbed by alkaline cement paste in SFP, enhancing the photocatalytic purification to NOx. NOx is purified to generate nitrate and H2O. However, Fe-doped TiO2 shows unsatisfactory photocatalytic purification efficiency to CO and CO2 due to their reversiblereactions, not following the pseudo-first-order kinetics reaction model. The Fe-doped TiO2 dosage of 8% is proposed to add in cement slurry for prepare photocatalytic SFP. The prepared Fe-doped TiO2 shows slight effects on pavement performances of SFP, and can be used in SFP to develop a new sustainable and green pavement material.