POLYANILINE (PANI)-SENSITIZED Fe3O4/SiO2/TiO2 NANOCOMPOSITES AS PHOTOCATALYST FOR THE REDUCTION OF Au(III) IONS

Abstract

Polyaniline (PANI)-sensitized Fe 3 O 4 /SiO 2 /TiO 2 nanoparticles were synthesized and the material then applied as a photocatalyst to reduce Au(III). The Fe 3 O 4 was synthesized through the sono-coprecipitation method using NH 4 OH as a precipitating agent. The coating of SiO 2 and TiO 2 onto the Fe 3 O 4 was then performed via a hydrolysis reaction and sol-gel process using ammonium peroxydisulfate as the initiator of the aniline polymerization. The parameters investigated in this work are the effect of medium acidity, equilibrium state and material responsiveness on visible light. The TEM images show that the photocatalyst had nanosized particles with an approximate size of 20.7 nm. The observed data from the activity test show the optimum pH and contact time of the photoreduction process were 5 and 180 minutes respectively. The effect of light exposure indicated that the polyaniline-sensitized Fe 3 O 4 /SiO 2 /TiO 2 was effective for Au(III) reduction in visible light up to 92% of the initial concentration. The effect of the material revealed that polyaniline-sensitized Fe 3 O 4 /SiO 2 /TiO 2 had better photocatalytic activity than that of TiO 2 and Fe 3 O 4 /SiO 2 /TiO 2 in visible, UV and dark conditions.