Environmental Applications of Nanocrystalline TiO₂ in Combination with H₂O₂

ABSTRACT

Heterogeneous photocatalysis using nanostructured semiconductors constitutes one of the emerging advanced oxidation processes (AOP) for destructive oxidation of organic contaminants in water or air. Herein we report the kinetics of potocatalytic degradation of nitrophenols (NPs), namely, o-nitrophenol (ONP), m-nitrophenol (MNP), and p-nitrophenol (PNP), using semiconductor photocatalyst TiO₂ in suspension, using laboratory-scale immersion well an ultraviolet (UV) photoreactor and the comparison of different advanced oxidation processes such as (i) UV + TiO₂ (ii) UV + TiO₂ + H₂O₂. In addition, the effect of several other parameters such as TiO₂ concentration, initial concentration of substrate solution, and effect of time of irradiation was investigated to arrive at optimum process parameters for complete degradation of the pollutants. UV light was found to have a negligible effect in the absence of the photocatalyst, TiO₂, whereas the percentage degradation of all three NPs was found to be drastically enhanced when H₂O₂ was added to the UV + TiO₂ system. The degradation rate followed a first-order kinetics.

KEYWORDS:

• photocatalysis
• TiO₂
• nitrophenols
• H₂O₂