RESUMEN
Water electrolysis is increasingly considered a viable solution for meeting the world's growing energy demands and mitigating environmental issues. An inventive strategy to mitigate the energy requirements involves substituting the energy-intensive oxygen evolution reaction (OER) with biomass-derived glycerol electrooxidation. Nonetheless, the synthesis of electrocatalysts for controlling the selectivity towards added-value chemicals at the anode and efficient H2 generation at the cathode remains a critical bottleneck. Herein, we implemented a galvanostatic electroshock synthesis approach to control the reduction kinetics of Au(III) and Pt(IV) to grow ultra-low amount of gold-platinum alloys on a gas diffusion electrode (12-26 µgmetal cmâ2) for glycerol-fed hydroxide anion exchange membrane based electrolyzer. The symmetric GDE-Au100-xPtx||GDE-Au100-xPtx systems showed a notable improvement in electrolyzer performance (GDE-Au64Pt36 = 201 mA cm-2) as compared to monometallic versions (GDE-Au100Pt0 = 18 mA cm-2, GDE-Au0Pt100 = 81 mA cm-2). Chromatography (HPLC) analysis underscores the critical importance of bulk electrolysis methodology (galvanostatic vs potentiostatic) for the efficient conversion of glycerol into high-value-added products. Regarding the electrical energy required to produce 1 kg of H2 for such an electrolyzer fed at the anode with glycerol, our results confirm a drastic decrease by a factor of at least two compared with conventional water electrolysis.
RESUMEN
The evolution of the degradation by-products of an acetaminophen (ACE) solution was monitored by HPLC-UV/MS and IC in parallel with its ecotoxicity (Vibrio fischeri 81.9%, Microtox® screening tests) during electro-Fenton (EF) oxidation performed on carbon felt. The aromatic compounds 2-hydroxy-4-(N-acetyl) aminophenol, 1,4-benzoquinone, benzaldehyde and benzoic acid were identified as toxic sub-products during the first stage of the electrochemical treatment, whereas aliphatic short-chain carboxylic acids (oxalic, maleic, oxamic, formic, acetic and fumaric acids) and inorganic ions (ammonium and nitrate) were well identified as non-toxic terminal sub-products. Electrogenerated hydroxyl radicals then converted the eco-toxic and bio-refractory property of initial ACE molecule (500 mL, 1 mM) and subsequent aromatic sub-products into non-toxic compounds after 2 h of EF treatment. The toxicity of every intermediate produced during the mineralization of ACE was quantified, and a relationship was established between the degradation pathway of ACE and the global toxicity evolution of the solution. After 8 h of treatment, a total organic carbon removal of 86.9% could be reached for 0.1 mM ACE at applied current of 500 mA with 0.2 mM of Fe2+ used as catalyst.
Asunto(s)
Acetaminofén/química , Acetaminofén/toxicidad , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/toxicidad , Aliivibrio fischeri/efectos de los fármacos , Compuestos de Amonio/química , Benzaldehídos/química , Benzaldehídos/toxicidad , Ácido Benzoico/química , Ácido Benzoico/toxicidad , Benzoquinonas/química , Benzoquinonas/toxicidad , Carbono/química , Ácidos Carboxílicos/química , Catálisis , Técnicas Electroquímicas , Electrodos , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Hierro/química , Cinética , Nitratos/química , Oxidación-Reducción , Fenoles/química , Fenoles/toxicidadRESUMEN
The degradation pathway of Acid Orange 7 (AO7) by Electro-Fenton process using carbon felt cathode was investigated via HPLC-UV and LC-MS, IC, TOC analysis and bioassays (Vibrio Fischeri 81.9% Microtox(®) screening tests). The TOC removal of AO7 reached 96.2% after 8 h treatment with the optimal applied current density at -8.3 mA cm(-2) and 0.2 mM catalyst concentration. The toxicity of treated solution increased rapidly to its highest value at the early stage of electrolysis (several minutes), corresponding to the formation of intermediate poisonous aromatic compounds such as 1,2-naphthaquinone (NAPQ) and 1,4-benzoquinone (BZQ). Then, the subsequent formation of aliphatic short-chain carboxylic acids like acetic acid, formic acid, before the complete mineralization, leaded to a non-toxic solution after 270 min for 500 mL of AO7 (1 mM). Moreover, a quantitative analysis of inorganic ions (i.e. ammonium, nitrate, sulfate) produced during the course of degradation could help to verify molar balance with regard to original nitrogen and sulfur elements. To conclude, a clear degradation pathway of AO7 was proposed, and could further be applied to other persistent pharmaceuticals in aquatic environment.