Electrochemical Degradation of Piroxicam on a Boron-Doped Diamond Anode: Investigation of Operating Parameters and Ultrasound Synergy

摘要

The electrochemical oxidation of piroxicam (PIR), a representative nonsteroidal anti-inflammatory drug, was studied using boron-doped diamond (BDD) as anode. BDD exhibited superior efficiency in comparison with platinum electrodes in terms of PIR degradation. Removal of PIR follows pseudo-first-order kinetics and the apparent kinetic constants decreased from 0.138 to 0.0369 min(-1) as the initial PIR concentration increased from 245 to 975 mu g L-1. Altering of the pH had little effect on electrolysis of PIR with slightly better removal at pH 9. The presence of 10 g L-1 of tert-butanol inhibited PIR removal, indicating that its oxidation is caused by electro-generated hydroxyl radicals. Addition of 200 mg L-1 sodium chloride increased the apparent kinetic constant more than ten times from 0.139 to 1.44 min(-1). Similar behavior was observed in the case of bicarbonates and nitrates, possibly due to the generation of selective carbonate radicals and active oxygen species like nitric or nitrous oxides. Experiments were also conducted in various aqueous matrices and it was observed that the presence of humic acid delayed the degradation of PIR, while process efficiency was enhanced in bottled and surface water as well as in wastewater, due to the presence of inorganic ions. Coupling BDD electrolysis with ultrasound (at 14 W L-1, 20 kHz) increased the reaction rate of PIR destruction and the observed synergy was calculated at S=44.6%.