Estudio Multifactorial y simulación de la degradación fotocatalítica de un fármaco

Abstract

Photocatalysis is an advanced oxidation process, which in recent decades has proven to be a suitable technology for water treatment, which allows the elimination of bio-resistant toxic organic compounds and achieve their complete mineralization; however, its industrial implementation has been hampered due to lack of clarity in its design and scaling; in addition to the difficulty of estimating the optical coefficients and parameters that intervene in the process of radiation absorption. Based on the above, it is important to develop calculation methods and computational tools to simulate the behavior of photocatalytic reactors, facilitate their study and select the most appropriate operating parameters that allow the process to be more efficient. In the present investigation, the photocatalytic degradation of paracetamol was experimentally performed. Mathematical modeling of the process was established to determine the intrinsic kinetic equation of photocatalytic degradation, which takes into account the effect of direct and indirect photolysis and that due to photocatalysis. And through computer simulation the impact of different parameters on the conversion was analyzed. In addition, a methodology was established to determine by simulation and experimental radiometric measurements optical coefficients and the coefficient of the phase function Henyey – Greenstein, under working conditions of the photocatalytic reactor employed. The parameters analyzed in this investigation were: a) Type of catalyst, since five different catalysts were analyzed: commercial TiO2 DP25, TiO2-Mo, TiO2-W and catalysts obtained from hydrotalcite-type compounds Mg-Zn-Al and Zn-Al; b) initial concentration of reagent; c) charge of catalyst; d) effect of the oxidizing agent; e) intensity of radiation emitted by the lamp and f) thickness of the reaction space. When experimentally performing the paracetamol degradation by UV light in the absence of a catalyst, it was found that paracetamol is susceptible to degradation by photolysis. For this reason it was necessary to modify the kinetic models proposed in the literature to take into account the degradation by photolysis. The results of the proposed kinetic model show a good concordance with the experimental data, both for the kinetics of degradation by photolysis and by photocatalysis using the TiO2 DP25 catalyst, since it was the only catalyst that presented catalytic activity under the conditions used in this investigation.