CHEMICAL ENGINEERING TRANSACTIONS VOL. 39, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Jiří Jaromír Klemeš, Peng Yen Liew, Jun Yow Yong Copyright © 2014, AIDIC Servizi S.r.l., ISBN 978-88-95608-30-3; ISSN 2283-9216 DOI: 10.3303/CET1439104 Please cite this article as: Vaiano V., Sacco O., Sannino D., Ciambelli P., 2014, Increasing the photoactivity of n-doped TiO2 photocatalysts using phosphors as light carriers, Chemical Engineering Transactions, 39, 619-624 DOI:10.3303/CET1439104 619 Increasing the Photoactivity of N-doped TiO 2 Photocatalysts Using Phosphors as Light Carriers Vincenzo Vaiano*, Olga Sacco, Diana Sannino, Paolo Ciambelli University of Salerno, Department of Industrial Engineering, Via Giovanni Paolo II, 132, 84084, Fisciano (SA), Italy. vvaiano@unisa.it The aim of the work was to increase the photoactivity of N-doped TiO2 photocatalyst, active in visible light region, through the improving of the illumination efficiency. Microradiators like phosphors (namely, ZPS) which absorb an electromagnetic radiation by the external light source (UV) and, with no time delay, emit visible light, opportunely selected to be able to excite N-doped TiO2 photocatalyst. Preliminary investigations were performed on physical mixtures of phosphors and N-doped TiO2, evaluating the decolourization of methylene blue (MB). The simultaneous presence of N-doped TiO2 and light carriers showed an increased decolourization activity, reaching about 100 % with a total TOC removal after 3 h of irradiation. To get core-shell photocatalysts, N-doped TiO2 was supported on ZPS (NTiO2-ZPS) by a modified sol–gel method. The content of N-doped TiO2 was varied in the range 5-50 wt % to find an optimum loading. The photocatalytic activity of NTiO2-ZPS was evaluated for the removal of MB under UV illumination. The performances of NTiO2-ZPS showed an improved efficiency in decolourization process of MB, equal to 100 % after 90 min of irradiation, with a total TOC removal. The influence of several parameters, such as dye type and concentration has been studied. 1. Introduction Textile dyes have become as toxic organic compounds the focus of environmental remediation efforts because of their natural biodegradability is increasingly troublesome owing to the improved properties of dyestuffs (Vajnhandl and Le Marechal, 2007). Colour interferes with penetration of sunlight into the water, retards photosynthesis, inhibits the growth of aquatic biota and interferes with solubility in water bodies (Vautier et al., 2001). Dyes removal using conventional oxidation methods is difficult, because a lot of pollutants are bio-recalcitrant (Souza et al., 2013, Šíma et al., 2013). Heterogeneous photocatalysis using oxide semiconductors is an interesting application owing to its potential in the resolution of environmental issues (Murcia et al., 2013, Bamuza-Pemu et al., 2013 Ruzmanova et al., 2013). The titanium dioxide (TiO2) semiconductor photocatalyst has the potential to oxidize a wide range of toxic organic compounds into harmless compounds such as CO2 and H2O by irradiation with UV light (Driessen and Grassian, 1998). Due to the value of its band-gap energy (3.0-3.3 eV), TiO2 absorbs about 5 % of sunlight in the UV region. A large number of approaches have been taken to reduce the band gap energy of TiO2, such as doping with transition metal cations (Inturi et al., 2013) or more recently, doping with anions such as C (Zhang et al., 2013), S (Han et al., 2011) and N (Sannino et al., 2013a). The N-doped TiO2 seems to be the most promising among all the so called second generation photocatalysts. However photocatalysts suffer for the layout of photocatalytic plants, where the most often found limitation regards the effective transferring of the light towards the overall amount of photocatalyst. The improving or a correct evaluation of the photocatalytic reactivity is correlated to wellness of the catalytic surface irradiation, and so the possibility to mix the photocatalyst with emitting phosphorescent particles (known generally as phosphors) as light carriers has been exploited (Ciambelli et al., 2011). In this case, the photocatalyst surface was completely irradiated (Sannino et al., 2013b) as shown by the considerably increase of the photocatalytic activity. The aim of this work was to investigate the effect of engineered coupling of N-TiO2 with blue phosphors in photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Reaction products were monitored both in liquid-phase, by decolourization and TOC analysis, and in gas-phase, by continuous analyses, measuring CO, CO2 and SO2 gaseous concentrations at the photo-reactor outlet.