Application of TiO<inf>2</inf>-based nanocomposites for simultaneous H<inf>2</inf> production and biodiesel wastewater remediation

Abstract

A series of titania (TiO2)-based nanocomposites was prepared for the simultaneous hydrogen (H2) production and pollutant removal from biodiesel wastewater. Three types of semiconductors, bismuth (III) oxide (Bi2O3), niobium pentoxide (Nb2O5), and tungsten trioxide (WO3), at different loading levels (1−8 mol%) were employed. The addition of the respective semiconductors enhanced the H2 production and chemical oxygen demand (COD) removal by the TiO2 nanoparticles. The B5/TiO2 nanocomposite (TiO2 with 5 mol% of Bi2O3) exhibited the highest H2 production (3.79 mmol), while the W5/TiO2 nanocomposite (TiO2 with 5 mol% of WO3) achieved the highest COD removal level (29.1 %) at a nanocomposite loading level in the photocatalytic reactor of 4 g/L with UV–vis irradiation of 5.93 mW/cm2 at 30 °C for 4 h. The addition of hydrogen peroxide (H2O2) enhanced the photocatalytic activity of the B5/TiO2 nanocomposite for both H2 production and pollutant removal. Approximately 31.92 mmol of H2 can be produced from the biodiesel wastewater with removal of around 32.8 % COD and 24 % oil & grease via the B5/TiO2 nanocomposite in the presence of 0.4 M H2O2, without the dissolution of the Bi2O3 semiconductor.