Pharmaceutical compounds photolysis: pH influence.

The operating parameters of photolytic and photocatalytic reaction processes directly affect the efficiency in the degradation of compounds. In particular, pH is a variable that needs to be considered as it exerts great influence on adsorption, absorption, solubility, among others. This study describes the application of the photolytic process, at different pHs, in the degradation of different pharmaceutical compounds. Photolytic reactions were performed with the following contaminants: acetylsalicylic acid (ASA), ibuprofen (IBP) and paracetamol (PAR). In addition, a comparison was performed using the commercial catalyst P25. The results indicated a great influence of the pH in the kinetic constant of the photodegradation and in the UV absorbance of the species. In particular, the degradation of ASA and PAR were favored with the reduction of pH, while the degradation of IBU and SA were favored by increasing. Also, the chromatograms indicated that pH may affect the by-products formed. In comparison, the photocatalysis process in the presence of P25 proved to be much more effective, but it was not possible to achieve complete mineralization of the compounds.