III International Conference

PP-I-76PHOTOCATALYTIC REDUCTION OF NITRATES DISSOLVED IN WATER OVERAg/TiO 2 CATALYSTSPrihod’ko R., Sychev M., Goncharuk V.Dumanski Institute of Colloid and Water Chemistry, Kiev, UkraineE-mail: r.v.prihodko@icccw.kiev.uaRelation between preparation procedure and catalytic behavior of Ag/TiO 2 catalysts innitrate reduction was studied. The materials with homogeneously distributed fine silverclusters showing high photocatalytic efficiency were synthesized by a triblock copolymerinduced reduction of [Ag(NH 3 ) 2 ] + under ambient light illumination. The effects of Agloading, carrier composition and nature of hole scavengers were systematically investigated.Using fomic acid as such agent, a nitrate conversion of 98 % and selectivity ca. 100 % can beachieved after 30 min of irradiation.From an environmental standpoint, one of the most acceptable methods for removal ofnitrates, which cause health hazards, is to convert them into N 2 . Recently developedphotocatalytic nitrate reduction using TiO 2 supported Ag nanoparticles [1, 2] is promisingapproach due to chemical stability, nontoxicity and low cost of the catalyst. In this reactionsilver enhances photocatalytic activity of titania promoting charge separation and inhibitingrecombination of electron–hole pairs, while sacrificial electron donors (hole scavengers) areessential for the reduction of NO3 - . However, it is still desirable to find out an appropriateprocedure for the catalyst preparation and optimal reaction conditions to produce a qualitystandard for drinking water.In this study, the influence of preparation mode potentially effecting photocatalyticbehaviour of Ag/TiO 2 materials in nitrate reduction was investigated. The procedures of thecatalyst activation, regeneration and reaction conditions providing maximum efficiency ofNO 3 - removal from water were also evaluated.The catalysts were prepared using different modifications of TiO 2 by a conventionalchemical reduction method, a pH-controlled photocatalytic process [1] and by a triblockcopolymer induced reduction of [Ag(NH 3 ) 2 ] + in ethanol [3] under ambient light illuminationof varied duration. In the later case, PEO 20 PPO 70 PEO 20 (Pluronic P123) and EO 97 PO 69 EO 97(Pluronic F127) surfactans were utilized. The silver content was varied between 0.5-2.5 wt %.The catalysts were characterized by means of ICP, X-ray diffraction, X-ray photoelectronspectroscopy, UV-ViS spectroscopy and transmission electron microscopy.143