Mineralization of Herbicides Imazapyr and Imazaquin in Aqueous Medium By, Fenton, Photo‐fenton and Electro‐fenton Processes

Abstract

Oxidative degradation of aqueous solutions of imazapyr and imazaquin herbicides at room temperature and pH 3.0 has been investigated by Fenton, photo-Fenton and electro-Fenton processes. The high degradation power of these advanced oxidation processes is due to the large production of hydroxyl radicals (*OH), a strong oxidizing agent, by reaction between H2O2 and Fe2+ in the solution to be treated. These radicals are used to oxidize organic pollutants to aromatic and aliphatic intermediates through subsequent oxidation until complete mineralization. Degradation kinetics and evolution of the chemical composition of treated solutions in each process was followed by high performance liquid chromatography. The mineralization efficiency was determined by chemical oxygen demand analysis. The effect of experimental parameters such as initial herbicide concentration, hydrogen peroxide concentration, ferrous ion concentration and applied current on the degradation kinetics was examined. Better degradation and mineralization efficiency were observed in photo-Fenton and electro-Fenton processes compared with conventional Fenton process. A pseudo-first order kinetic model was employed to describe the result and determine the apparent and absolute rate constants of the reaction between hydroxyl radicals and herbicides.

Oxidation/mineralization of 2-Nitrophenol in aqueous medium by electrochemical advanced oxidation processes using Pt/carbon-felt and BDD/carbon-felt cells

“…The decrease of the mineralization degree by increasing applied current can be related to the consumption of a significant part of the supplied electrical energy by acceleration of side reactions taking place in anode and cathode. In fact, additionally to the oxidation of H 2 O 2 (formed at carbon-felt cathode) (reactions (6) and (7)), the kinetics of the sides reactions such as direct oxidation of M( Å OH) to O 2 (reaction (8)), or indirect consumption through dimerization to H 2 O 2 (reaction (9)), generation of the weaker oxidant O 3 (reaction (10)) or oxidation of sulfate ions (reactions (11) and (12)) will be accelerated by rising the applied current [19,23].…”

“…Direct photochemistry is not efficient either [7], while ozonolysis is quite slow [8]. In contrast, advanced oxidation processes (AOPs), which involve the highly oxidizing agent hydroxyl radicals ( Å OH), such as: H 2 O 2 photolysis [9], Fenton's reagent [2,5], photo-Fenton [10][11][12], and heterogeneous photocatalysis [13] were shown to be able to degrade efficiently nitrophenols.…”

Integration of Solar Photocatalysis and Membrane Bioreactor for Pesticides Degradation

“…Photo-Fenton has been demonstrated to be an effective AOP treatment to degrade contaminants (9,10,11,12). It is based on the Fenton reaction to generate HO radicals.…”

Toxicity assessment of tannery effluent treated by an optimized photo-Fenton process

“…In particular, the photo-Fenton process, which uses a reagent mixture of hydrogen peroxide (H 2 O 2 ), ferrous ion (Fe 2+ ) and UV light, is one of the most important processes among AOPs, provoking several pathways in order to attack and degrade organic pollutants [8]. The photo-Fenton process is regarded as a newly emerging AOP, which has recently been applied to the treatment of tannery waste [6,9], food processing wastewaters [10], wood processing wastewaters [11], herbicides [12], pesticides [13], pharmaceutical pollutants [14], organic compounds [15], landfill [16] and dyes [17][18][19], among others.…”