Azadirachta indica leaves extract assisted green synthesis of Ag-TiO2 for degradation of Methylene blue and Rhodamine B dyes in aqueous medium

Abstract

Aqueous pollution due to textile industry is an important issue. Photocatalysis is one of the methods used for eradication of dyes from textile industrial effluents. In this study, the synthesis, characterization and evaluation of photo catalytic activity of Ag-TiO2 is reported. TiO2 catalysts with 2, 4, 6 and 8% loading of Ag were prepared by green methods using Azadirachta indica leaves extract as reducing agent with titanium dioxide and silver nitrate as precursor materials. Prepared catalyst was characterized by advanced techniques and was used as catalyst for degradation of Methylene blue and Rhodamine B dyes. Deposition of Ag greatly enhanced the catalytic efficiency of TiO2 towards degradation of dyes. Irradiation of catalyst excites electrons from conduction band of catalyst to valence band yielding an electron-hole pair. This electron-hole pair undergoes secondary reactions and produce OH• radicals. These active radicals take part in degradation of dyes. More than 90% dyes were degraded in 120 min. Photo catalytic degradation of Methylene blue and Rhodamine B followed Eley-Rideal mechanism which states that dye react in fluid phase with adsorbed oxygen.