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

Abstract

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 À 1 as the initial PIR concentration increased from 245 to 975 μg L À 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 À 1 of tert-butanol inhibited PIR removal, indicating that its oxidation is caused by electro-generated hydroxyl radicals. Addition of 200 mg L À 1 sodium chloride increased the apparent kinetic constant more than ten times from 0.139 to 1.44 min À 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 À 1 , 20 kHz) increased the reaction rate of PIR destruction and the observed synergy was calculated at S = 44.6 %. order to keep temperature of the water below 35°C after 15 min of sonoelectrocatalysis. Liquid ChromatographyPIR was detected by modifying an HPLC method, described in our previous work. [48] The chromatographic system was a Waters Alliance 2695 connected with a Waters 2996 PDA detector. The column was a Kinetex XB-C18 100A column (2.6 μm, 2.1 mm × 150 mm and was connected with a 0.5 μm inline filter (KrudKatcher Ultra) (Phenomenex). The flow rate was 0.2 mL/min and the mobile phase consisted of 75 : 25 acetonitrile water. The column was thermostated to 45°C. The injection volume was 100 μL. After the separation, the concentration of PIR was measured using Waters 2996 Photo Diode Array detector at 350 nm.

Degradation of the Nonsteroidal Anti-Inflammatory Drug Piroxicam by Iron Activated Persulfate: The Role of Water Matrix and Ultrasound Synergy

“…The flow was 0.2 mL/min with 25:75 acetonitrile and 0.1% phosphoric acid. The detector that was used to monitor the absorbance of Piroxicam at 350 nm was a photodiode array (model 2996, Waters, Milford, MA, USA) [ 26 ].…”

“…Lower-frequency ultrasound at 20 kHz was capable of degrading up to 960 μg/L of PIR in less than 30 min using 36 W/L ultrasound power density. Kouskouki and coworkers [ 26 ] studied the electrochemical oxidation of piroxicam on a Boron-Doped Diamond. The electrochemical oxidation was capable of removing piroxicam in short treatment times (i.e., less than 15 min for the removal of 245 μg/L of Piroxicam at 26.7 mA/cm 2 ).…”

Coupling Persulfate-Based AOPs: A Novel Approach for Piroxicam Degradation in Aqueous Matrices

“…Chloride radicals may contribute, besides sulfate and hydroxyl radicals, to the degradation of the pollutant; nonetheless, high concentrations of chloride ion may behave as radical scavengers leading to a detrimental effect [43]. Indeed, the presence of 200 mg/L chloride increased the apparent kinetic constant of piroxicam electrochemical oxidation by almost ten times [52]. A similar behavior was observed by Outsiou et al [53], where the addition of more than 50 mg/L chloride increased the removal of bisphenol A using SPS activated by a bimetallic carbon xerogel catalyst.…”

Coupling a Boron Doped Diamond Anode with a Solid Polymer Electrolyte to Avoid the Addition of Supporting Electrolyte in Electrochemical Advanced Oxidation Processes

“…Therefore, the idea behind the cell introduced above is to pair a solid membrane, which provides ionic conductivity, and electroactive electrode for oxidizing organic compounds. Among them boron doped diamond (BDD) is widely study for its excellent properties . In fact, it has wide potential window, high‐oxygen‐overvoltage anodes, inert surface with low surface adsorption properties and good corrosion stability also in aggressive environment .…”