Electro-Fenton degradation of the antibiotic sulfanilamide with Pt/carbon-felt and BDD/carbon-felt cells. Kinetics, reaction intermediates, and toxicity assessment

Abstract

The degradation of 230 mL of a 0.6-mM sulfanilamide solution in 0.05 M Na₂SO₄ of pH 3.0 has been studied by electro-Fenton process. The electrolytic cell contained either a Pt or boron-doped diamond (BDD) anode and a carbon-felt cathode. Under these conditions, organics are oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between initially added (and then electrochemically regenerated) Fe(2+) and cathodically generated H₂O₂. From the decay of sulfanilamide concentration determined by reversed-phase liquid chromatography, an optimum Fe(2+) concentration of 0.20 mM in both cells was found. The drug disappeared more rapidly using BDD than Pt, and, in both cases, it was more quickly removed with raising applied current. Almost total mineralization was achieved using the BDD/carbon-felt cell, whereas the alternative use of Pt anode led to a slightly lower mineralization degree. In both cells, the degradation rate was accelerated at higher current but with the concomitant fall of mineralization current efficiency due to the greater increase in rate of the parasitic reactions of hydroxyl radicals. Reversed-phase liquid chromatography allowed the identification of catechol, resorcinol, hydroquinone, p-benzoquinone, and 1,2,4-trihydroxybenzene as aromatic intermediates, whereas ion exclusion chromatography revealed the formation of malic, maleic, fumaric, acetic, oxalic, formic, and oxamic acids. NH₄(+), NO₃(-), and SO₄(2-) ions were released during the electro-Fenton process. A plausible reaction sequence for sulfanilamide mineralization involving all detected intermediates has been proposed. The toxicity of the solution was assessed from the Vibrio fischeri bacteria luminescence inhibition. Although it acquired its maximum value at short electrolysis time, the solution was completely detoxified at the end of the electro-Fenton treatment, regardless of the anode used.

Removal of psychoactive pharmaceutical caffeine from water by electro-Fenton process using BDD anode: Effects of operating parameters on removal efficiency

“…1 shows that the degradation of caffeine was complete at about 4-6 min for all current intensities (except 50 mA) with 0.2 mM Fe 2+ . This value agrees with previous reports [13,39] and was taken as an optimal catalyst value for the following experiments.…”

Effect of the anode materials on the efficiency of the electro-Fenton process for the mineralization of the antibiotic sulfamethazine

“…The Electro-Fenton process presents several advantages compared to the classical Fenton's system such as (i) in-site production of H2O2 that avoids the risks related to its transport, storage and handling, (ii) high oxidation/mineralization efficiency of organics due to the continuous electro-generation of the catalyst (Fe 2 ), (iii) easy control of the degradation kinetics, (iv) nonuse of harmful of chemical reagents and absence of formation of process sludge, and (iv) feasibility of total mineralization by optimizing the operating parameters [19], [28], [29] and [30].…”

Comparative use of anodic oxidation, electro-Fenton and photoelectro-Fenton with Pt or boron-doped diamond anode to decolorize and mineralize Malachite Green oxalate dye

“…H 2 O 2 (2) Carbonaceous cathodes are the most efficient electrodes for the two-electron reduction of O 2 to H 2 O 2 from reaction (2). Examples of such cathodes include graphite [16], carbon sponge [17], graphite felt [18,19], carbon felt [5,[20][21][22], activated carbon fiber [23,24], carbon-polytetrafluoroethylene (PTFE) gas diffusion [25][26][27], carbon nanotubes [28] and BDD [29][30][31].…”