Treatment of diclofenac in aqueous solution by electro-oxidation using BDD electrodes

Abstract

The consumption of pharmaceutical products such as non-steroidal anti-inflammatories, including 2- [2- (2,6-dichloroanilino) phenyl] acetic acid, better known as diclofenac, has been increasing due to its easy acquisition, as a consequence the environment has had repercussions since it is excreted through the urine, causing a potential risk to be discharged into water bodies and creating persistence in the environment and in the processes of wastewater treatment. Therefore, it is necessary to use alternative processes of advanced oxidation because they have proven to be efficient in the degradation of xenobiotic compounds. The objective of this research was to apply an electro-oxidation system and photoelectro-oxidation by boron-doped diamond (BDD) electrodes using a BDD-BDD configuration to determine the operation variables for the oxidation of diclofenac in aqueous solution. The optimal conditions of the study were: current intensity of 1 A (current density (J) = 25.29 A / m²), the pH of the sample (5-6); NaCl as supporting electrolyte, in the absence of UV light, and treatment time of 360 minutes. The removal efficiency of diclofenac was 97.8 %, the TOC, COD showed efficiencies of 64.4 % and 89.3 %, respectively, whereas the biochemical oxygen demand (BOD₅) decrease after of treatment. The degradation kinetic of diclofenac was adjusted to a pseudo first order model, with a half-life time of 63.89 minutes and a k = 1.08 x 10^-2 min^-1. The removal percentages of diclofenac using liquid chromatography (HPLC) were 99.64 %, 98.76 % and 95.15 % for the concentrations of 150, 50 and 10 mg/l, respectively.