Degradation of Atrazine by Electrochemical Advanced Oxidation Processes Using a Boron-Doped Diamond Anode

Abstract

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 O(2) diffusion cathode able to generate H(2)O(2). Hydroxyl radicals ((*)OH) formed at the BDD surface in all EAOPs and in the bulk from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2) 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(-), NO(3)(-), and NH(4)(+) have been followed by ionic chromatography.

Removal of atrazine and its by-products from water using electrochemical advanced oxidation processes

“…This result indicates that a high 529 fraction of ATZ and other fractions of some refractory organic matter were completely oxidized 530 into water, giving carbon dioxide and inorganic ions. The consumed specific charge (Q, in Ah L ) by Borràs et al (2010). In these conditions (2.8 Ah L -1 at 420 min), highM A N U S C R I P T…”

“…According to Borràs et al (2010), the number of carbon atoms of ATZ and the 261 number of electrons consumed during the mineralization was shown in this reaction (Eq. (10)) : 262…”

“…This behaviour can be explained because CA is 514 one of the most persistent by-products from ATZ degradation and having low reactivity with 515 hydroxyls radicals (Borràs et al 2010, Oturan et al 2012). In the other hand, the CA can be 516 removed with a high current density such as 50 and 40 mA cm -2 (Borràs et al 2010, Oturan et al 517 2012. This argument justified why in this study after 420 min of treatment, the concentration of 518 CA did not decrease in our electrochemical cell, despite that a current density imposed of 18.2 519 mA cm -2 .…”

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU

“…Photo-electro-Fenton was found to be more effective than electroFenton using a carbon polytetrafluoroethylene cathode (Borrás et al, 2010). Pentachlorophenol (together with other chlorophenols not included in the Directive 2013/39/EU was subjected to electro -Fenton using a Pt anode and a carbon felt cathode ) with oxidation through attack of HO • on ortho and para chlorine positions and subsequent mineralization.…”

Effect of Nitrate and Sulfate Contamination on Degradation of Diuron via Electrochemical Advanced Oxidation in a Microreactor

“…Diuron contaminating in water can be treated by several techniques, such as bio-degradation [8], adsorption [9], and several kinds of advanced oxidation processes (AOPs) which employ highly reactive hydroxyl radicals (OH) to oxidize the contaminant [10][11][12][13]. Electrochemical advanced oxidation process (EAOP) is also an AOP that produces hydroxyl radicals via dissociation of water at an anode, when electrical potential is applied to the electrodes.…”