Chemometric study on the TiO2-photocatalytic degradation of nitrilotriacetic acid.

A chemometric study on the TiO2-photocatalytic degradation of nitrilotriacetic acid (NTA) in aqueous media under UV radiation has been carried out taking into account the multiple variables that take part in the system. To save redundant number of experiments, the system has been managed under chemometric techniques for several variables as NTA and TiO2 concentrations, pH and irradiation time. Multiple-way analysis of the variance (MANOVA) has been applied to find the statistically significant variables. An artificial neural network (ANN) has been used to build an empirical model of the system. All measurements have been driven under experimental designs: a full-factorial design (FFD) was used to analyze significant factors through MANOVA, and a Doehlert design, which was modified by spatial rotation, was applied in order to have a satisfactory number of levels for the factor time to be able to train the ANN. The study allows the knowledge and prediction of the behavior of the system as well as to work out kinetic parameters and to optimize their variables. The results of kinetic parameters obtained with the neural network agreed with independent experimental results, confirming a Langmuir-Hinshelwood kinetic regime. The difference between NTA and ethylenediaminetetraacetic acid (EDTA), which has been previously studied, is also established.

Phenol photodegradation on platinized-TiO2 photocatalysts related to charge-carrier dynamics.

Three commercial TiO2 compounds (Degussa P25, Sachtleben UV100, and Millenium PC50) and their platinized forms have been studied by the time-resolved microwave conductivity (TRMC) method to follow their charge-carrier dynamics and to relate it to the photocatalytic activity for phenol degradation in TiO2 aqueous suspensions. The degradation reaction has been studied in detail, following the time evolution of the concentration of phenol and its intermediates by liquid chromatography. The results show that platinization has a distinct influence on the commercial compounds, decreasing globally the activity of P25 and increasing the activity of PC50 and UV100. An influence of charge-carrier lifetimes on the photoactivity of pure and platinized TiO2 samples has been evidenced.