Procesos Electroquímicos de Oxidación Avanzados en la degradación de los ácidos trans-cinámico y trans-ferúlico

En este artículo, se discutirá la degradación de los ácidos trans-cinámico y trans-ferúlico a través de procesos electroquímicos de oxidación avanzados (PEOAs) tales como la oxidación anódica con H2O2 electro generado (OA-H2O2), electro-Fenton (EF) y fotoelectro-Fenton (FEF). En un reactor de tanque agitado, a 25 ° C, equipado con un ánodo de 3 cm2 de diamante dopado con boro (BDD) y un cátodo de carbono de difusión de aire de politetrafluoroetileno de 3 cm2, se electrolizó 100 ml de soluciones conteniendo 200 mg L-1 de carbono orgánico total (COT) en Na2SO4 0.05 M a pH 3.0 aplicando densidades de corriente desde 16.67 hasta 100 mA cm-2 durante 360 minutos. En los experimentos de EF y FEF, se añadió Fe2+ 0.50 mM como catalizador de la reacción de Fenton, mientras que en FEF, la solución se irradió con luz UVA. La capacidad de oxidación de los ácidos con los PEOAs aumentó en secuencia OA-H2O2<EF<FEF para ambos ácidos. Se observó mayor degradación del ácido trans-cinámico durante los PEOAs. A pesar que las moléculas del ácido trans-cinámico y ácido trans-ferúlico, poseen una estructura química similar, éstos se degradaron de forma muy diferente entre sí con los PEOAs aplicado

Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode

The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O2-diffusion cathode for H2O2 generation. The main oxidizing species are OH radicals formed at the BDD surface in all treatments and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF. A poor mineralization was attained using AO-H2O2 by the slow oxidation of persistent by-products with OH at the BDD surface. The synergistic action of OH in the bulk enhanced the degradation rate in EF, although almost total mineralization was only achieved in PEF due to the additional OH generation and photolysis of intermediates by UVA irradiation. The effect of current, pH and herbicide concentration on the mineralization degree and mineralization current efficiency of each EAOP was examined. Desmetryne decay always followed a pseudo first-order kinetics, being more rapidly destroyed in the sequence AO-H2O2 < EF < PEF. In all EAOPs, ammeline and cyanuric acid were identified as persistent heteroaromatic by-products and oxamic and formic acids were detected as generated carboxylic acids. The generation of cyanuric acid mainly by oxidation with OH at the BDD surface is the predominant path for desmetryne degradation. The initial nitrogen of desmetryne yielded NO 3 ion in low proportion and NHþ4 ion in much lesser extent, suggesting that its major part was lost as volatile N-derivatives.Peer ReviewedPostprint (published version

Degradation of atrazine by electrochemical advanced oxidation processes using a boron-doped diamond anode

Solutions of 30 mg L-1 of the herbicide atrazine have been degraded by environmentally friendly electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) using a small open and cylindrical cell with a boron-doped diamond (BDD) anode. AO has been carried out either with a stainless steel cathode or an O2 diffusion cathode able to generate H2O2. Hydroxyl radicals (•OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF are the main oxidants. All treatments yielded almost overall mineralization, although the rate for total organic carbon (TOC) removal is limited by the oxidation of persistent byproducts with •OH at the BDD surface. In AO, TOC abatement is enhanced by parallel electrochemical reduction of organics at the stainless steel cathode, while in PEF, it also increases from additional photolysis of intermediates by UVA light under the synergistic action of •OH in the bulk. The effect of current and pH on the degradative behavior of EAOPs has been examined to determine their optimum values. Atrazine decay always follows a pseudo-first-order reaction, being more rapidly destroyed from •OH in the bulk than at the BDD surface. Aromatic intermediates such as desethylatrazine, desethyldesisopropylatrazine, and cyanuric acid and short linear carboxylic acids such as formic, oxalic, and oxamic have been identified and quantified by reversed-phase and ion-exclusion HPLC, respectively. Released inorganic ions such as Cl-, NO3-, and NH4 + have been followed by ionic chromatography.Peer ReviewedPostprint (published version

Degradation of atrazine by electrochemical advanced oxidation processes using a boron-doped diamond anode

Solutions of 30 mg L-1 of the herbicide atrazine have been degraded by environmentally friendly electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) using a small open and cylindrical cell with a boron-doped diamond (BDD) anode. AO has been carried out either with a stainless steel cathode or an O2 diffusion cathode able to generate H2O2. Hydroxyl radicals (•OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF are the main oxidants. All treatments yielded almost overall mineralization, although the rate for total organic carbon (TOC) removal is limited by the oxidation of persistent byproducts with •OH at the BDD surface. In AO, TOC abatement is enhanced by parallel electrochemical reduction of organics at the stainless steel cathode, while in PEF, it also increases from additional photolysis of intermediates by UVA light under the synergistic action of •OH in the bulk. The effect of current and pH on the degradative behavior of EAOPs has been examined to determine their optimum values. Atrazine decay always follows a pseudo-first-order reaction, being more rapidly destroyed from •OH in the bulk than at the BDD surface. Aromatic intermediates such as desethylatrazine, desethyldesisopropylatrazine, and cyanuric acid and short linear carboxylic acids such as formic, oxalic, and oxamic have been identified and quantified by reversed-phase and ion-exclusion HPLC, respectively. Released inorganic ions such as Cl-, NO3-, and NH4 + have been followed by ionic chromatography.Peer Reviewe

Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode

The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O2-diffusion cathode for H2O2 generation. The main oxidizing species are OH radicals formed at the BDD surface in all treatments and in the bulk from Fenton’s reaction between added Fe2+ and electrogenerated H2O2 in EF and PEF. A poor mineralization was attained using AO-H2O2 by the slow oxidation of persistent by-products with OH at the BDD surface. The synergistic action of OH in the bulk enhanced the degradation rate in EF, although almost total mineralization was only achieved in PEF due to the additional OH generation and photolysis of intermediates by UVA irradiation. The effect of current, pH and herbicide concentration on the mineralization degree and mineralization current efficiency of each EAOP was examined. Desmetryne decay always followed a pseudo first-order kinetics, being more rapidly destroyed in the sequence AO-H2O2 < EF < PEF. In all EAOPs, ammeline and cyanuric acid were identified as persistent heteroaromatic by-products and oxamic and formic acids were detected as generated carboxylic acids. The generation of cyanuric acid mainly by oxidation with OH at the BDD surface is the predominant path for desmetryne degradation. The initial nitrogen of desmetryne yielded NO 3 ion in low proportion and NHþ4 ion in much lesser extent, suggesting that its major part was lost as volatile N-derivatives.Peer Reviewe