DEVELOPING NEW SEMICONDUCTOR PHOTOCATALYSTS FOR DYE WASTEWATER TREATMENT

Abstract

The Sillén-Aurivillius hybrid layered perovskites, Bi4 La3NbO8X (X = Cl, Br: y = 0, 1) have been synthesized via solid state reaction. The compounds are characterized by powder X-ray diffraction (PXD), Field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and photoluminescence spectroscopy (FL). The band gaps of the compounds lie in the range of 2.1 - 2.7 eV, as revealed from the UV-Vis DRS. The photocatalytic degradation studies over these catalysts show excellent photodegradation efficiency toward RhB in the acidic medium (p1-I 2), and MB in neutral and alkaline condition (p11 7 and p1-1 11) under natural sun-light irradiation. 014 and h are found to be the main reactive species responsible for high photocatalytic activity, as revealed from the scavenger tests performed during dye degradation. Besides, the relative position of conduction and valence band edges of semiconductors, HOMO-LUMO levels of RhB and position of OH/H20, 02/02 levels show that the photodegradation efficiency is mainly decided by the holes. in the simple perovskite series, few new compositions with general formulas, PbBiiTiFe1 03 (x = 0.5. 0.25) and Pb1 BiTi1 ,2Fe1203 (x = 0.5, 0.75) are also explored via solid state reactions. The photocatalytic activity studies over these Pb-Bi-Ti-Fc-O systems show high efficiency toward RhB degradation in the acidic medium. Further, the Sillén-Aurivillius hybrid layered perovskites are assessed for their activity toward real dye wastewater and have been found to be effective in COD removal up to 90% within 150 rnin of sun-light irradiation.