PHOTOCATALYTIC ACTIVITY OF ZnO/TiO2 COMPOSITES IN CIRCULATING CONDITIONS

Abstract

The development of new efficient photocatalysts is an important task for solving problems related to the purification of water and air from organic pollution. Composite materials based on ZnO and TiO2 exhibit high photocatalytic activity, which makes them promising for this application. In this work, we present the synthesis and study of the photocatalytic activity of ZnO/TiO2 composites obtained by the method of intermediate hydroxide deposition. The synthesis was carried out on the surface of Evonik P25 TiO2 with three different mass ratios of ZnO to TiO2: 1:3, 1:1, and 3:1. The resulting composites were studied by X-ray diffraction (XRD), spectroscopy to determine the optical band gap, and subjected to photocatalytic decomposition under circulating conditions. It was confirmed by XRD that ZnO crystallizes in the wurtzite phase of hexagonal syngony, and TiO2 is contained in the form of two modifications: anatase and rutile. The effect of the mass ratio of ZnO to TiO2 on the optical band gap has been studied. The optical band gap of ZnO/TiO2 composites was determined using the Kubelka-Munk algorithm. For the composites (1)ZnO/TiO2 and (3)ZnO/TiO2, the bandgap was 3.22 eV, and the lowest value (2.99 eV) was obtained for the composite with an equal ratio of ZnO to TiO2 - (2)ZnO/TiO2. The photocatalytic activity of ZnO/TiO2 composites was studied under circulating conditions with congo red dye in the presence of four different composite weights: 0.2, 0.4, 0.6, and 2 g. The maximum efficiency of photocatalytic decomposition of the dye was observed for the composite with an equal ratio of ZnO to TiO2 at a dosage of 2 g of the composite per 0.075 g of dye. The synthesized ZnO/TiO2 composites exhibit high photocatalytic activity, which makes them promising materials for water and air purification from organic pollution. The optimum mass ratio of ZnO to TiO2 for the photocatalytic decomposition of congo red dye is 1:1.