III International Conference

PP-I-76Photocatalytic reaction was carried out as described in Ref. [1] with initial concentrationof nitrate anions 23 mg N l -1 (calculated by nitrogen weight). The catalytic activity wasdefined as the amount of nitrate anions reduced per minute and active metal weight.Over all catalysts under study, no nitrate reduction was observed without a holescavenger. The use of formic acid as sacrificial electron donor greatly improved both thereaction rate and selectivity for nitrogen avoiding formation of undesirable nitrite andammonium ions. The amount of HCOOH equal to 0.02-0.04 mol l -1 was sufficient to reducenitrate totally. The highest catalytic activity was observed for the catalysts derived from TiO 2with mixed anatase-rutile composition. This fact indicates importance of hetero- junctionexisted in Ag/TiO 2 multiphase nanocomposite for enhancement of its photocatalytic activity.The preparation procedure significantly effects catalyst efficiency towards nitratereduction. The samples prepared via a triblock copolymer induced reduction of [Ag(NH 3 ) 2 ] +in ethanol under ambient light illumination are the most active. Depending on the carrierstructure, composition, grain size and silver loading, the average activity was ca. 40-70 mmolNO - 3 g -1 Ag min -1 . Enhanced dispersion of strongly anchored silver nanoparticles to the surfaceof TiO 2 can be considered as a possible explanation for this finding. Composition of triblockcopolymer also controls activity of the Ag/TiO 2 catalyst, which is higher in the case ofPluronic P123. By repeating the ambient light radiation, the deactivated catalysts could beregenerated again. The catalyst regeneration efficiency depends on both the titaniacomposition and duration of illumination. All these results showed the impact of studiedaspects on denitrification properties of Ag/TiO 2 nanocomposite catalyst.References1. F. Zhang, R. Jin, J. Chen, C. Shao, W. Gao,.L. Li, and N. Guan, J Catal. 232 (2005) 424.2. R. Prihod’ko, V.Goncharuk, M. Sychev, A. Lozovski, I. Stoljarova and I. Ledenev, UkrainianPatent Application 01862 (21.02. 2006).3. L. Zhang and J. C. Yu, Catal. Commun. 6 (2005) 684.144