Photocatalytic activity of metal nanoparticle-decorated titanium dioxide for simultaneous H<inf>2</inf> production and biodiesel wastewater remediation

Abstract

A set of metal nanoparticle-decorated titanium dioxide (Mx/TiO2; where x is the percent by mass, %) photocatalysts was prepared via the sol-immobilization in order to enhance the simultaneous hydrogen (H2) production and pollutant reduction from real biodiesel wastewater. Effect of the metal nanoparticle (NP) type (M = Ni, Au, Pt or Pd) and, for Pd, the amount (1 %–4 %) decorated on the surface of thermal treated commercial TiO2 (T400) was evaluated. The obtained results demonstrated that both the type and amount of decorated metal NPs did not significantly affect the pollutant reduction, measured in terms of the reduction of chemical oxygen demand (COD), biological oxygen demand (BOD) and oil & grease levels, but they affected the H2 production rate from both deionized water and biodiesel wastewater, which can be ranked in the order of Pt1/T400 > Pd1/T400 > Au1/T400 > Ni1/T400. This was attributed to the high difference in work function between Pt and the parent T400. However, the difference between Pt1/T400 and Pd1/T400 was not great and so from an economic consideration, Pd/TiO2 was selected as appropriate for further evaluation. Among the four different Pdx/TiO2 photocatalysts, the Pd3/TiO2 demonstrated the highest activity and gave a high rate of H2 production (up to 135 mmol·h−1) with a COD, BOD and oil & grease reduction of 30.3%, 73.7% and 58.0%, respectively.