Degradation of Dipyrone by Electrogenerated H₂O₂Combined with Fe²⁺Using a Modified Gas Diffusion Electrode

Abstract

The aim of the present study was to investigate the electrochemical degradation of dipyrone in a single compartment electrochemical cell equipped with a gas diffusion electrode (GDE) modified with cobalt (II) phthalocyanine. Degradations were performed under conditions of anodic oxidation (GDE pressurized with N 2 ) and under conditions promoting the electrogeneration of H 2 O 2 (GDE pressurized with O 2 ) both in the absence and presence of 1 mmol FeSO 4 .7H 2 O (electro-Fenton conditions). The efficiency of the electro-Fenton process was satisfactory at all studied potentials, and achieved a maximum reduction of 67% in electrolyte absorbance at 262 nm after 90 min electrolysis at −0.7 V (vs. Ag/AgCl). The reduction in dipyrone concentration attained 95% after 90 min of reaction with electrogenerated H 2 O 2 in the absence or presence of Fe 2+ ions at all potentials except −0.5 V (vs. Ag/AgCl). The removal of total organic carbon (TOC) was most efficient under electro-Fenton conditions with a decrease of 54.4% in organic load attained at -0.9 V (vs. Ag/AgCl) and energy consumption (EC) of 270 kWh per kg of TOC removed. The increase in levels of human and veterinary drugs and metabolites detected in urban sewage represents an issue of growing concern. Pollution of surface and ground water by pharmaceutical products can occur via a number of mechanisms including incorrect disposal of expired drugs, metabolic excretion of medications, or the discharge of effluent from the cleaning and decontamination of machinery and equipment involved in drug production. [1][2][3][4][5][6][7][8] Although the effects of drugs on the organisms to which they are administered have been widely studied, the undesirable consequences of the presence of these molecules and their corresponding metabolites in the environment remain poorly understood.9-11 It is, therefore, essential to minimize the pollution of the environment by such compounds.The pharmaceuticals most commonly encountered as contaminants in wastewater systems are non-steroidal anti-inflammatories, such as acetylsalicylic acid, diclofenac and dipyrone (DIP), since these medications are consumed in the largest quantities by the general population.6,11 Dipyrone (syn. metamizole), for example, is used widely as an analgesic and antipyretic in various countries in Europe, Africa and South America, although it has been banned in North America and some European countries because of its potential collateral effects. 2,[12][13][14][15][16] In view of the reported increase in the level of pharmaceutical pollution, it is clearly of paramount importance to develop methodologies that could prevent contact between these biologically active compounds and the environment. Unfortunately, the techniques currently employed in the treatment of public sewage are not able to remove completely these types of compounds from aqueous medium. A number of alternative methods are available for the removal of drugs from wastewaters, 17 but straightforward approaches such as incineration generally involv...

Tailoring the ORR selectivity for H2O2 electrogeneration by modification of Printex L6 carbon with 1,4-naphthoquinone: a theoretical, experimental and environmental application study

“…For the detection of H 2 O 2 , the working electrode ring was polarized at +1.0 V Ag/AgCl , as proposed by some authors. 26,51,52 This overpotential applied promoted the oxidation of H 2 O 2 , exhibiting a current proportional to the amount of H 2 O 2 involved.…”

“…In all the samples employed in this investigation, sodium bisulfite was used to remove all residual H 2 O 2 and to halt the drug degradation reaction. 32,52 Degradation monitoring…”

Oxidative Degradation of Pharmaceuticals: The Role of Tetrapyrrole-Based Catalysts

“…Most prescribed analgesics include anti-inflammatory drugs, which reduce inflammation (e.g., ibuprofen, diclofenac, acetaminophen derivatives and salicylic acid, known as nonsteroidal anti-inflammatory drugs), and opioid analgesics, which change the way the brain perceives pain (e.g., tramadol). These types of drugs are commonly encountered in municipal wastewaters since they are consumed in quite high quantities by the general population [55,56].…”

The Analgesic Metamizol (Dipyrone). Part 2: Adsorption, Oxidative and Reductive Degradation

“…Some work has been done to either electrochemically generate H 2 O 2 [5,6] or to degrade metamizol using supported electrodes [7,8,9,10]. Reis et al [7] used anodes comprising boron-doped diamond films supported on titanium in a flow-by reactor.…”