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

Abstract

Groundwater is one of the main freshwater resources on the Earth, but its contamination by NO3 − and pesticides jeopardizes its suitability for consumption. In this work, the simultaneous electro-oxidation of insecticide imidacloprid (IMC) and electroreduction of NO3 − in softened groundwater containing a large amount of Cl − has been addressed. The assays were carried out in a stirred undivided tank reactor containing either a boron-doped diamond (BDD) or IrO2 anode, and Fe cathode, which showed greater electrocatalytic activity than stainless steel to reduce NO3 − . Comparative assays in simulated water mimicking the anionic composition of groundwater were made to assess the influence of natural organic matter (NOM) on the decontamination process. The BDD/Fe cell had much greater performance than the IrO2/Fe one, although the former produced larger amounts of ClO3 − and ClO4 − . In all cases, the NO3 − , Cl − and IMC decays agreed with a (pseudo)-first-order kinetics. In the BDD/Fe cell, total NO3 − removal was reached at j ≥ 10 mA cm -2 in softened groundwater, at similar rate in the presence and absence of IMC, but it was decelerated using the simulated matrix. The N-products formed upon NO3 − electroreduction contributed to IMC degradation, but its decay was inhibited by NOM because of the partial consumption of oxidants like hydroxyl radical and active chlorine.Operating at 5 mA cm -2 for 240 min, total removal of the insecticide and 61.5% total organic carbon (TOC) decay were achieved, also attaining a low NO3 − content that was suitable for humans. Eight heteroaromatic products were identified, allowing the proposal of a reaction sequence for IMC degradation in groundwater.

Comparison of two different nickel oxide films for electrochemical reduction of imidacloprid

“…Comparing these results with literature, the removal rate of IMD (equivalent to 4.81 mg L À1 min À1 ) observed in this study at an initial IMD of 100 mg L À1 and much lower current density of 0.10 mA cm À2 , was much higher than the rate achieved on a boron-doped diamond anode at a much higher current density by EAOPs. [27][28][29] In addition, $OH generation on anodic oxidation during EAOPs processes at high-voltage anodes means high electric price or low current efficiency compared to the results of this study with fairly high current efficiency.…”

ZnO/TiO2/Ag2Se nanostructures as photoelectrocatalysts for the degradation of oxytetracycline in water

“…(i) the presence of NOM in the main form of fulvic and humic acids with a TOC of 9.1 mg C dm -3 , which can partly consume the hydroxyl radicals [65], and (ii) the generation of active chlorine species such as HClO from oxidation of Cl − present in the medium via reactions (12) and ( 13), which act as scavengers of P( • OH) and attack the organics producing stable and toxic chloroderivatives [66,67].…”

Hazardous wastes treatment technologies

“…The percentage of nitrate removal was 96.8% after 3 h. Adsorption of the electroactive species and electrochemically active surface area contributed to the enhancement of nitrate reduction. Oriol, Bernicola, Brillas, Cabot, and Sires (2019) studied the simultaneous electro‐oxidation of insecticide imidacloprid (IMC) and electroreduction of in softened groundwater containing a large amount of Cl ‐ . A stirred undivided tank reactor equipped with either a boron‐doped diamond (BDD) or IrO 2 anode, and Fe cathode showed excellent electrocatalytic activity in reducing .…”