Photodegradation of sodium naproxen and oxytetracycline hydrochloride in aqueous medium using as photocatalysts Mg-Al calcined hydrotalcites

Layered double hydroxides (LDH) MgAl with different MII/MIII ratios were synthesized by the co-precipitation method. The materials were calcined at 723 K and characterized by XRD, nitrogen adsorption, UV–vis DRS and FTIR. The catalytic activity of the calcined solids was tested in the photodegradation of two water soluble pharmaceuticals: sodium naproxen, a non-steroidal anti-inflammatory, and oxytetracycline hydrochloride, a tetracycline family antibiotic. The synthesized solids mineralize rapidly both pharmaceuticals using UV as light source and after 5 h of reaction, about 90% of sodium naproxen and 70% of oxytetracycline hydrochloride were degraded by the catalyst with the higher photoactivity. Comparative studies were performed with TiO2 P25 commercial semiconductor. The results showed that the MgAl calcined hydrotalcites have a greater photoactivity in the degradation of the target molecules than TiO2. Fluorescence spectroscopy study suggests the generation of hydroxyl radicals as the oxidative species of the target molecules when MgAl calcined hydrotalcites are irradiated.