Removal of Naproxen in liquid phase by Using Advanced Oxidation Processes (AOPs)

The occurrence and the fate of pharmaceuticals residues in wastewater treatment and in the environment has attracted an increasing interest during the last decade and have posed a new challenge to professionals for wastewater recovery as well as to the pharmaceutical industry. The removal of many of pharmaceutical compounds, during municipal wastewater treatment, has showed to be incomplete and unsuitable. As a result, residues of these compounds have been detected in surface waters in concentrations ranging from the ng L-1 up to the mg L-1 level. Advanced Oxidation Processes (AOP) are commonly designed to produce hydroxyl radicals (HO•) that react efficiently with most organic compounds present in the water. Heterogeneous Photo-catalysis has emerged as viable alternative for removing micro-pollutants and other organic contaminants from surface, ground and wastewater. The catalyst used in this study was the semiconductor titanium dioxide (TiO2) chosen for its properties: high resistance to corrosion, low toxicity and low costs. However, a separation of the fine TiO2 catalysts after treatment can be energy intensive and time consuming, resulting in a significant reduction in the benefits of this technique in water treatment industries. This technical constraint leads to development of an immobilized photocatalyst on an inert support (thin blue glass sheets) to avoid costly separation processes after treatment. The aim of this work was the application of photo-catalysis for the degradation of Naproxen [(+)-S-2-(6-methoxynaphthalen-2-yl) propanoic acid]. This pharmaceutical compound is a Non-Steroidal Anti-Inflammatory (NSAI) drug and it is one of the most frequently found as recalcitrant in surface waters. It is widely prescribed for the skeleton-muscle pain or inflammatory rheumatic disorders due to its analgesic and antipyretic effects. Photochemical reactions were carried out by using a solar simulator and kinetic parameters were determined. Identification of the photoproducts was performed by liquid chromatography system coupled to a hybrid linear quadrupole ion trap (LTQ) – Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. The standard solution used as control in the darkness did not show any significant degradation during the experimental time. Data of the Naproxen degradation fitted well a pseudo first order kinetic curve (Table1). Six photoproducts have been successfully identified. There is no dimeric photoproducts. The photochemical reaction was observed to lead to decarboxylation followed by oxidation, resulting in the production of alcohol and ketone analogs of naproxen.