Photocatalytic Degradation of Sodium Diclofenac Using Spinel Ferrites: Kinetic Aspects

Abstract

The photocatalytic degradation of sodium diclofenac, a nonsteroidal anti-inflammatory drug, was carried out comparing the activity of cobalt, nickel, and zinc ferrites as catalysts, using UV radiation and hydrogen peroxide. The materials were characterized by X-ray diffraction and by Fourier-Transform Infrared, UV–Visible and X-ray photoelectron spectroscopies. It was determined that all samples had spinel structure: ZnFe2O4 normal spinel, CoFe2O4 partially inverse spinel and NiFe2O4 inverse spinel. A simulated solution of 40 ppm of sodium diclofenac was completed degraded within 4 h meanwhile 86 to 83% of total organic carbon was obtained. The photocatalytic process take place via radical mechanism. The decrease of samples pH could be attributed to the formation of small acid molecules like oxalic and acetic acid, which are by-products of sodium diclofenac photodegradation. The reaction kinetic was also studied, and the photo-Fenton degradation of sodium diclofenac could be described by first-order model with a linear correlations coefficient R2 > 0.95 in all cases. The information based on kinetic studies can be applied for developing reactors for pollutant elimination, especially for industrial scale.