Photocatalyzed destruction of aniline in UV-illuminated aqueous TiO2 suspensions

The photocatalytic oxidation of aniline in aqueous suspensions of TiO2 under UV-illumination is studied. The process follows a Langmuir-Hinshelwood kinetic model with an adsorption constant of 1.1 x 10(3) dm(-3) mol(-1) and a reaction rate constant of 8.3 x 10(-7) mol dm(-3) s(-1). The yield of photodegradation strongly depends on pH; higher yields are reported at very acid and basic media and also at pHs near the point of zero charge of TiO2. On the other hand, the yield of the photodegradation increases with the addition of small amounts of Fe2+ in solution. Hydrohydroquinone is the main intermediate product detected, phenol, paraquinone and nitrobenzene being other minor products formed during irradiation. Under illumination, the organic nitrogen is transformed to the inorganic forms: predominantly NH4+ at acid pH, while NO2- and NO3- appear at higher pHs. Percentages of TOC reduction of about 85% are attained after 8 h of irradiation of aniline solutions at pH 3 and 6 in the presence of TiO2. (C) 1997 Elsevier Science Ltd.