Kinetics and Products of Air Plasma Induced Oxidation in Water of Imidacloprid and Thiamethoxam Treated Individually and in Mixture

Abstract

+39 0498271608Imidacloprid (I) and thiamethoxam (T) are widely used neonicotinoid insecticides with high persistence in the environment and thus included in the watch list of substances for European Union-wide monitoring reported in the Decision 2015/495/EU. In this work we report and discuss the results of a study in which aqueous solutions of I, T and I + T were subjected to advanced oxidation by air plasma produced by negative DC corona discharges above the liquid surface. The oxidative degradation of each pollutant was investigated by monitoring the rate and the products of its decay when treated alone and in the presence of variable amounts of the other compound. The results show that both I and T are readily degraded and that mineralization can be achieved in this process, as proven by the measurement of the residual organic carbon and by the quantitative conversion of chlorine and sulfur into inorganic chloride and sulfate, respectively.The major organic intermediates formed during the complex stepwise oxidation of I and T were identified and monitored by HPLC-MS/MS analysis. The results of kinetic studies show that both for I and T the reaction rate depends inversely on the insecticide initial concentration, that I and T have similar reactivities and that they do not interfere reciprocally in any specific way when treated in mixture at a total concentration of ca 10 -4 M. Based on literature data and on previous results with the same reactor, it is reasonable to propose that the oxidation of I and T is initiated by the reaction with OH radicals.

Can we remove tattoos with non‐thermal atmospheric plasma?

“…Several works focused on advanced oxidation processes for dyes and pollutant decomposition reported a linear dependence of the degradation constant with the inverse of the starting concentration. [22,23] By assuming the same behavior, on the basis of the half-life time that we measured in the experiment reported in Figure 2d for liquid gelatin samples (about 5 h), we can conclude that the discoloration of tattoo pigments by reaction of the oxidant species generated by plasma would be practically impossible (a treatment should last 20-200 days). To increase the NTP oxidative effect more energetic treatment would be required (higher applied power or treatment time), but this could also lead to the potentially harmful thermal effects observed in the solid gelatin disks (Figures 3 and S3).…”

Comment on “Water-Soluble Fluorescent Probe with Dual Mitochondria/Lysosome Targetability for Selective Superoxide Detection in Live Cells and in Zebrafish Embryos”

“…1 We are interested in applying this probe to determine superoxide in advanced oxidation processes induced by air non thermal plasma. [12][13][14][15][16][17] In repeating some of the experiments used by Lu et al 1 to characterize the probe's behavior, we realized that the procedure they applied to perform experiments with KO2 as a surrogate for superoxide is not appropriate and led them to misinterpret their results. The present comment addresses this issue and provides and discusses experimental evidence of interest for users of this and all related probes for superoxide.…”

Salicylic Acid Elimination by Pulsed Corona Discharge Treatment of Wastewater

“…Therefore, depending on the discharge properties and the gas utilized, a variety of reactive species acting as powerful oxidizers are formed besides hydrated electrons and photons. With air, reactive oxygen compounds (e.g., OH • , , O, H 2 O 2 , O 3 ) plus HONOOH and are formed with no need for UV lamps or chemicals and can assist in effectively destroying organic compounds or transform them into safe products 27–30.…”