Visible light active Bismuth ferrite embedded TiO2 nanocomposite structures for dye mineralization by photocatalysis -A strategy to harness solar energy for remediation of water contaminated with mixture of dyes

Harnessing solar energy to treat effluents from industries in order to mineralize the organic pollutants by photocatalysis demands the use of photocatalysts which are visible light active. In the present study, Bismuth ferrite embedded TiO2 (BFO/TiO2) nanocomposites have been synthesized with BFO (prepared by co-precipitation method) to Ti molar ratio of 1:2. BFO/TiO2 nanocomposites are crystalline, oval shaped and monodispersed with the average hydrodynamic diameter of 42 nm. Transmission Electron Microscopy (TEM) revealed that BFO nanoparticles have an average shorter dimension of 13.4 nm and longer dimension of 15.5 nm and are embedded in TiO2 matrix with the average coating thickness of 4.8 nm. The apparent band gap energy of BFO/TiO2 is 1.8 eV. BFO/TiO2 nanocomposites were used for the degradation of dyes from mixed dye aqueous solution containing three azo dyes, viz. Methylene Blue (MB), Acid yellow-17 (AY- 17), and Rhodamine- B (Rh-B) dyes under visible light irradiation. The BFO/TiO2 nanocomposites exhibited good photocatalytic activity under visible and solar light. Around 92% of MB, 73.9% of AY-17 and 68.3% of Rh-B dyes were degraded in 210 min from the mixed dye aqueous solution. Chemical Oxygen Demand (COD) removal of 72% could be achieved by photocatalysis confirming the mineralization of dyes. The COD removal kinetics followed first order model with the rate constant of 0.006 min- 1. BFO/TiO2 nanocomposites exhibited superior visible light activity compared to BFO or TiO2 (Degussa P25) nanoparticles. The BFO/TiO2 nanocomposites have been proven to be promising in remediation of wastewater contaminated with mixture of dyes by photocatalysis.