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

摘要

Polyaniline (PANI)-sensitized Fe3O4/SiO2/TiO2 nanoparticles were synthesized and the material then applied as a photocatalyst to reduce Au(III). The Fe3O4 was synthesized through the sono-coprecipitation method using NH4OH as a precipitating agent. The coating of SiO2 and TiO2 onto the Fe3O4 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 Fe3O4/SiO2/TiO2 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 Fe3O4/SiO2/TiO2 had better photocatalytic activity than that of TiO2 and Fe3O4/SiO2/TiO2 in visible, UV and dark conditions.