The Effects of Some Operational Parameters in Photodegradation of Benzylamine and Aniline and Their Kinetics in Aqueous Suspension of TiO2 and Pt–Loaded TiO2

Abstract

Photocatalytic degradation of benzylamine and aniline on TiO₂, Pt-modified TiO₂, ZnO and ZnS in aqueous solution has been investigated. The degradation of the compounds follows a pseudo-first-order kinetics according to Langmuir-Hinshelwood model. The degradation process of benzylamine and aniline was evaluated by ninhydrin spectrophotometric method using UV-visible spectrophotometer in λmax= 538 and 525 nm, respectively. The results showed the order of Pt/TiO₂> TiO₂> ZnO> ZnS for photocatalytic activity. In addition increasing of the Pt-loading was found to enhance the degradation rate of the compounds up to the optimal amount of 5wt. % onto the surface of TiO₂ so that the rates of degradation were increased about two times. Rate constants for photodegradation of benzylamine and aniline were found to be 1.4×10^-3 min^-1 and 0.7×10^-3 min^-1 for TiO₂ as photocatalyst, while 2.7×10^-3 min^-1 and 1.7×10^-3min^-1 for (5 wt.%) Pt/TiO₂ as photocatalyst. Running the reactions in various pH (5-11), indicated that the pH= 8 and 10 or Higher are the optimum pH for photocatalytic degradation of benzylamine and aniline respectively. The effects of some other parameters such as amount of photocatalyst, flux of oxygen and irradiation time were evaluated. Furthermore, the Langmuir-Hinshelwood rate constant k_r and adsorption constant K_A for the titled compounds are reported.