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

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

Use of CO as a cleaning tool of highly active surfaces in contact with ionic liquids. Ni deposition on Pt(111) surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding surface contamination for experiments in ionic liquid (IL) media,. A room temperature ionic liquid (RTIL) and a Deep Eutectic Solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]) and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is oxidised easily to CO2 in [Emmim][Tf2N], in DES CO remains adsorbed on the substrate and restructures undergoing an order-disorder transition. For both liquids, the proposed method allows obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on Pt(111) surface was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques such as cyclic voltammetry and chronoamperometry, and the deposits were characterized by FE-SEM ,EDS and XPS

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

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

Use of CO as a cleaning tool of highly active surfaces in contact with ionic liquids. Ni deposition on Pt(111) surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding surface contamination for experiments in ionic liquid (IL) media,. A room temperature ionic liquid (RTIL) and a Deep Eutectic Solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]) and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is oxidised easily to CO2 in [Emmim][Tf2N], in DES CO remains adsorbed on the substrate and restructures undergoing an order-disorder transition. For both liquids, the proposed method allows obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on Pt(111) surface was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques such as cyclic voltammetry and chronoamperometry, and the deposits were characterized by FE-SEM ,EDS and XPS