Abstract
The increasing occurrence of antibiotics and their metabolites in surface and ground waters is causing a significant impact on the environment and needing of developing novel treatments for the complete removal of such contaminants. This paper presents the study of the electrogeneration of hydrogen peroxide (H2O2) in acidic medium and the degradation of the analgesic dipyrone in an electrochemical flow reactor using a gas diffusion electrode (GDE) modified with 5.0% cobalt (II) phthalocyanine (CoPc) and pressurized with O2. The highest yield of H2O2 (133 mg L-1) was achieved after 90 min of electrolysis at an applied potential of -2.1 V (vs. Pt//Ag/AgCl/KCls) and the best results for degradation of dipyrone were obtained under electro-Fenton conditions, where the total organic carbon (TOC) was reduced 62.8% after 90 min of reaction and 49.1 kW h of energy was consumed per kg of dipyrone degraded.
Highlights
Drugs that have been administered to humans are excreted either unchanged or in the form of metabolites
The increased current observed when the gas diffusion electrode (GDE) was pressurized with O2 may be associated with the reduction of H+ ions and O2 to form H2O2, other reactions may occur in parallel under these conditions including the reduction of O2 to water via a 4-electron transfer.[22,24,29]
A plot of the difference between the linear voltammetry (LV) recorded under O2 and N2 pressurization (Figure 1B) revealed that, the oxygen reduction reaction (ORR) current increased with increasing applied potential and attained a value of -1.6 A at -2.8 V
Summary
Drugs that have been administered to humans are excreted either unchanged or in the form of metabolites. Conventional treatments of sewage water are not able to remove these compounds completely,[1,2] and contamination of surface and ground water by pharmaceutical products has been reported in a number of countries.[3,4,5,6,7,8] Various classes of drugs have been implicated as sources of environmental pollution, but non-steroidal anti-inflammatory drugs (NSAIDs) such as acetylsalicylic acid, diclofenac and dipyrone (DP) are generally detected in the largest quantities. Recent concerns about environmental pollution have engendered renewed interest in the development of techniques that would promote the complete removal of recalcitrant contaminants from sewage waters. In the case of DP, the kinetics of photodegradation of metabolites of the drug in aqueous systems have been established.
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