Electrochemical Oxidation of Pharmaceuticals on a Pt-SnO2/Ti Electrode

The application of an advanced oxidation process, electrochemical oxidation, was evaluated for the degradation of the non-steroidal anti-inflammatory substance, diclofenac (DCF), by using an electrode (anode) of Pt-SnO2 on a titanium substrate (Pt-SnO2/Ti). An increased decomposition rate of DCF was recorded. Different experimental parameters such as current intensity, initial concentration of substrate, irradiation, and pH were evaluated. The effects of bicarbonate and chloride ions and humic acid (HA) were also assessed. It was found that the electrochemical degradation follows pseudo-first-order kinetic with respect to the initial substrate concentration. The kinetics rate constant was shown to increase with increasing chloride concentration and current intensity, while it decreased with increasing initial DCF concentration. Additionally, the results showed that the concentration of bicarbonate ions slightly diminishes the process yield, while ultraviolet A (UVA) irradiation does not accelerate DCF decomposition. In contrast, lower pH values contributed to faster degradation of the target substance. The effect of the aqueous matrix was also evaluated. A higher rate of DCF decomposition within a shorter time interval was recorded when secondary effluent (WW) was used. On the contrary, HA was found to slow down the process. Finally, experiments were carried out to investigate the degradation of another pharmaceutical, sulfamethoxazole (SMX). It was found that SMX was degraded at 73.1% in 30 min, while for the same time; the abatement of DCF was 44.5%. This study demonstrates the efficiency of electrochemical oxidation for the abatement of pharmaceuticals with an anode of platinum-tin dioxide on titanium substrate in water matrices.