Past and Present Research Systems of Green Chemistry

Biography

Biography: Asmae Bouziani

Abstract

The development of new photocatalysts is attracting vast interest. Among them the Bismuth tungstate (Bi₂WO₆) is a typical n-type direct band gap semiconductor with a band gap of 2.75 eV and has prospective applications in electrode materials, solar energy conversion and catalysis. In addition it has been found that Bi₂WO₆ might act the same as a stable photocatalyst for the photochemical decomposition of organic contaminants under visible light irradiation. The present study intended to dope Bi₂WO₆ with Fe₂O₃ to prepare Bi₂WO₆-Fe₂O₃ composite and investigate the degradation mechanisms of the composite in the presence of H₂O₂. Methyl orange (MO) is used to imitate no biodegradable, toxic organic compounds. The photocatalytic activity of Bi₂WO₆-Fe₂O₃ to MO in the absence and presence of H₂O₂ is evaluated. Bi₂WO₆-Fe₂O₃ composites were synthesized using a mechanical mixing; by adding the Bi₂WO₆ obtained by hydrothermal method to the corresponding amount of Fe₂O₃ and their photocatalytic activity to degrade methyl orange (MO) under visible light illumination supported with H₂O₂ were studied. The H₂O₂ react with photogenerated electrons leading to the production of hydroxyl radicals (OH^●). The Fe₂O₃ acts like a Fenton reagent, accelerating the production of OH^●. Bi₂WO₆-Fe₂O₃/ H₂O₂ system demonstrate much higher photocatalytic efficiency to degrade MO than pure Bi₂WO₆. 50% of MO was degraded in 120 min visible irradiation and the peak disappeared after 90 min, and in Bi₂WO₆-Fe₂O₃ system the peak disappeared after 90 min. This study was performed at pH≈ 6 using Fe₂O₃ as a heterogeneous photo-Fenton catalyst in neutral and weak alkaline conditions of wastewater.