Enhanced Eosin Mineralization in Presence of Au(III) Ions in Aqueous Solutions Containing TiO2 as Suspension

Abstract

Photo-catalytic mineralization of eosin in aerated 0.1% (w/v) TiO 2 suspended aqueous systems with and without Au 3+ using 350 nm photo light was carried out. Eosin mineralization rate was significantly faster in 2´10 -4 M Au 3+ containing systems in contrast to sole TiO 2 systems, which is due to the participation of Au 3+ and it’s in situ generated various reduced intermediates including gold nanoparticles during mineralization. Furthermore, pulse radiolysis (a well known transient measurement technique) was adopted to analyze the reaction intermediates (eosin-OH adducts and/or eosin radical cation) produced in mineralization by generating in situ · OH and N 3 · species. The reaction rates for · OH and N 3 · reactions with eosin evaluated respectively 5.4´10 9 and 3.0´10 9 dm 3 mol -1 s -1 for the formation of radical cations were slower than the eosin-OH adduct formation rate (reaction rate = 1.4´10 10 dm 3 mol -1 s -1 ). Furthermore, it is proposed that the initially generated eosin- · OH/hole adduct is undergoing mineralization in the presence of air/oxygen.