Ensuring the overall combustion of herbicide metribuzin by electrochemical advanced oxidation processes. Study of operation variables, kinetics and degradation routes

Abstract

This article reports the electrochemical degradation of the herbicide metribuzin (MTZ) in sulfate medium by advanced oxidation processes like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). A boron-doped diamond (BDD) anode was combined with an air-diffusion cathode with ability to produce H2O2. Unprecedented overall combustion was feasible by all methods at a constant current density (j) ≥ 100.0 mA cm -2 . The total organic carbon (TOC) removal achieved by AO-H2O2 was independent from pH within the range 3.0-9.0, whereas the oscillatory dependence of the pseudo-first-order MTZ decay rate constant with this variable was ascribed to adsorption on the BDD surface. In EF and PEF at pH 3.0, 0.50 mM Fe 2+ was determined as optimum catalyst content and the MTZ removal showed two consecutive pseudo-first-order kinetic stages. These were related to the fast reaction of the target molecule with • OH formed from Fenton's reaction, followed by a slower attack of physisorbed BDD( • OH) onto Fe(III)-MTZ complexes. The effect of j and MTZ content on decay kinetics and TOC removal was examined. PEF was the best treatment due to the decomposition of photoactive intermediates by UVA radiation, yielding total mineralization of a 0.523 mM herbicide solution after 420 min of electrolysis at 100.0 mA cm -2 . A thorough reaction pathway for MTZ degradation is proposed from the sixteen heteroaromatic by-products and three aliphatic molecules identified by GC-MS and LC-MS/MS. Oxalic and oxamic acids were detected as final carboxylic acids by ion-exclusion HPLC.

Expanding the application of photoelectro-Fenton treatment to urban wastewater using the Fe(III)-EDDS complex

“…Peaks appeared at tr of 1.75 min (F − ), 2.5 min (Cl − ) and 4.0 min (NO3 − ). The NH4 + concentration was obtained as reported elsewhere (Guelfi et al, 2019b).…”

Performance Evaluation of Fenton Based Processes in Reducing COD of the Petroleum Effluents Using the Waste of Steel Slag

“…shown their high potential in removing various contaminants (Villanueva-Rodríguez et al, 2014;Brillas and Martínez-Huitle, 2015;Flores et al, 2016;Steter, Brillas and Sirés, 2016;Komtchou et al, 2017;Moreira et al, 2017;Aveiro et al, 2018;Guelfi et al, 2019;Thiam and Salazar, 2019;Ye et al, 2019). Some studies have investigated the effect of the similar cathode and anode electrode (such as identical electrodes of Na 2 SO 4 (Babuponnusami and Muthukumar, 2012b); graphite electrodes (Nidheesh and Gandhimathi, 2014) and identical BBD electrodes (Villanueva-Rodríguez et al, 2014) in the Fenton based processes and achieved good results.…”

Paired electro-oxidation of insecticide imidacloprid and electrodenitrification in simulated and real water matrices

“…The efficient removal of several pesticides from synthetic solutions by electrochemical advanced oxidation processes (EAOPs) like electro-oxidation (EO), electro-Fenton (EF) and photoelectro-Fenton (PEF) using BDD or DSA  anodes has been reported [26][27][28][29][30][31][32][33]. In contrast, less is known about the treatment of pesticides in groundwater, since as far as we know only the treatment of lindane and IMC has been reported [34,35].…”