Application of Advanced Oxidation Processes to Mefenamic Acid Elimination

The elimimation of mefenamic acid has been carried out by photolysis, ozonation, adsorption onto activated carbon (AC) and combinations of the previous single systems (O3+AC and O3+UV). The results obtained indicate that mefenamic acid is not photo-reactive, showing a relatively low quantum yield of the order of 6 x 10-4 mol Einstein-1. Application of ozone to mefenamic aqueous solutions instantaneously eliminates the pharmaceutical, achieving simultaneously a 40% of mineralization. Addition of AC to the ozonation process does not enhance the process, moreover, mineralization is completely inhibited if compared to results obtained by single ozonation. The combination of ozone and UV radiation led to the best results in terms of mineralization (60% after 120 min).

Aqueous Ranitidine Elimination in Photolytic Processes

The elimination of ranitidine (a pharmaceutical compound) has been carried out in the presence of UV-C radiation. After some preliminary experiments, it has been experienced the no influence of the gas nature (air or oxygen) bubbled in photolytic experiments. From simple photolysis experiments the quantum yield of this compound has been determined. Two photolytic approximation has been used, the linear source emission in parallel planes and the point source emission in spherical planes. The quantum yield obtained was in the proximity of 0.05 mol Einstein-1 regardless of the method used. Addition of free radical promoters (hydrogen peroxide) increases the ranitidine removal rate while the use of photocatalysts (TiO2) negatively affects the process.

Catalytic Decomposition of Potassium Monopersulfate. The Kinetics

Potassium monopersulfate has been decomposed in aqueous solution in the presence of Co(II). The process has been simulated by means of a mechanism based on elementary reactions. Rate constants have been taken from literature reports or, alternatively, assimilated to analogous reactions occurring in Fenton's chemistry. Several operating conditions have been successfully applied.

Catalytic Decomposition of Potassium Monopersulfate. Influence of Variables

Potassium monopersulfate has been decomposed in aqueous solution in the presence of Co(II). The effect of the main operating variables has been assessed. Minimum variations in pH exert a considerable influence on the process kinetics. Thus, when no pH adjustment is considered, the actual effect of variables like initial monopersulfate and/or catalyst concentration may be hindered. As expected, temperature enhances the monopersulfate decomposition rate by following the Arrhenius law. The activation energy in the proximity of 85 kJ/mol has been obtained. Amongst the different solids tested in the monopersulfate decomposition, only the perovskite LaTi0.15Cu0.85O3 has shown a significant catalytic activity.