In this paper, visible light assisted degradation of various pollutants using different methods has been briefly reviewed. These methods have been broadly divided into two main categories. In the first category, the use of TiO2 semiconductor facilitating the photooxidative degradation of organic pollutants has been presented. This semiconductor has been treated in several ways. A major aim of these treatments is to maximize the range of wavelength in the visible light region for wastewater treatment. In the second category, various ways of degrading organic pollutants without the use of TiO2 semiconductor have been briefly outlined. The role of Fe(II)/Fe(III), etc., species in the sensitization process of various substrates helping it in the process to photocatalytic degradation reactions of organic pollutants has been highlighted. Also, the usage of semiconductors other than TiO2 has been critically analyzed.

Visible light induced photocatalytic degradation of organic pollutants

Systemic insecticides are applied to plants using a wide variety of methods, ranging from foliar sprays to seed treatments and soil drenches. Neonicotinoids and fipronil are among the most widely used pesticides in the world. Their popularity is largely due to their high toxicity to invertebrates, the ease and flexibility with which they can be applied, their long persistence, and their systemic nature, which ensures that they spread to all parts of the target crop. However, these properties also increase the probability of environmental contamination and exposure of nontarget organisms. Environmental contamination occurs via a number of routes including dust generated during drilling of dressed seeds, contamination and accumulation in arable soils and soil water, runoff into waterways, and uptake of pesticides by nontarget plants via their roots or dust deposition on leaves. Persistence in soils, waterways, and nontarget plants is variable but can be prolonged; for example, the half-lives of neonicotinoids in soils can exceed 1,000 days, so they can accumulate when used repeatedly. Similarly, they can persist in woody plants for periods exceeding 1 year. Breakdown results in toxic metabolites, though concentrations of these in the environment are rarely measured. Overall, there is strong evidence that soils, waterways, and plants in agricultural environments and neighboring areas are contaminated with variable levels of neonicotinoids or fipronil mixtures and their metabolites (soil, parts per billion (ppb)-parts per million (ppm) range; water, parts per trillion (ppt)-ppb range; and plants, ppb-ppm range). This provides multiple routes for chronic (and acute in some cases) exposure of nontarget animals. For example, pollinators are exposed through direct contact with dust during drilling; consumption of pollen, nectar, or guttation drops from seed-treated crops, water, and consumption of contaminated pollen and nectar from wild flowers and trees growing near-treated crops. Studies of food stores in honeybee colonies from across the globe demonstrate that colonies are routinely and chronically exposed to neonicotinoids, fipronil, and their metabolites (generally in the 1–100 ppb range), mixed with other pesticides some of which are known to act synergistically with neonicotinoids. Other nontarget organisms, particularly those inhabiting soils, aquatic habitats, or herbivorous insects feeding on noncrop plants in farmland, will also inevitably receive exposure, although data are generally lacking for these groups. We summarize the current state of knowledge regarding the environmental fate of these compounds by outlining what is known about the chemical properties of these compounds, and placing these properties in the context of modern agricultural practices.

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Environmental fate and exposure; neonicotinoids and fipronil

https://www.boerenlandvogels.nl/sites/default/files/Morrissey%20et%20al_2015_Neonicotinoid%20contamination%20of%20global%20surface%20water%20%20%20.pdf

Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates: A review

In this article, the decade of electroanalysis with bismuth-based electrodes is reviewed (with 222 refs) Emphasis is put on the environmentally friendly (“green”) character of bismuth electrodes, their versatility and variability in use, as well as the actual classification of the individual types of electrodes, sensors, and detectors that utilize the unique properties of metallic bismuth Of particular interest is the genesis of the field, when the respective activities and achievements are monitored year by year over the whole period of 2000–2009, including the circumstances of the introduction of bismuth-coated electrodes into electrochemical stripping analysis The review highlights all the significant milestones and break-points that had directed the experimental work around the globe, outlining the present day's position of this lively, inspiring, and still highly prospective area Finally, it provides a special insight into electroanalysis with bismuth electrodes through numerous surveys, summaries, and detailed statistical data obtained by analyzing the accessible literature database

A Decade with Bismuth‐Based Electrodes in Electroanalysis

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high-energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy-storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double-layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene-based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene-based asymmetric supercapacitors. The challenges and prospects of graphene-based supercapacitors are also discussed.

https://hal.archives-ouvertes.fr/hal-02045769/document

Nanoarchitectured Graphene‐Based Supercapacitors for Next‐Generation Energy‐Storage Applications

A simple voltammetric method using a glassy carbon working electrode was developed for the determination of two members from the neonicotinoid group of insecticides: imidacloprid and thiamethoxam. The experiments showed that the voltammetric response depends on the mode of electrode surface pretreatment and the polarization mode. The response appeared to be linear in the range from 0.028 to 0.50 mg/cm 3 for both analytes. The limit of detection was 0.0077 mg/cm 3 for imidacloprid and 0.0085 mg/cm 3 for thiamethoxam, the limit of quantitation was 0.026 mg/cm 3 and 0.028 mg/cm 3 , respectively. The developed method was applied for the determination of these insecticides in potato samples sprayed with Confidor 200-SL or Actara 25-WG as well as commercial formulations of imidacloprid and thiamethoxam. A recovery trial was performed to assess the accuracy of the results, the recovery values being between 95 102 % for both of neonicotinoids.

/pdf/voltammetric-determination-of-imidacloprid-and-thiamethoxam-4by8ypa26h.pdf

Voltammetric determination of imidacloprid and thiamethoxam

An electroanalytical method has been developed for the determination of two water soluble pyridine based neonicotinoid insecticides (imidacloprid and acetamiprid) by differential pulse voltammetry with a bismuth film electrode in aqueous Britton – Robinson buffer solution as supporting electrolyte. The bismuth film electrode preparation was optimized for cathodic voltammetric application. The reduction peaks of the neonicotionids appeared at potentials more negative than � 0.5 V (BiFE vs. Ag/AgCl/3.0 M KCl) and the signal characteristics depended on the pH of the supporting electrolyte. The best analysis conditions were found to be pH 8.0 for imidacloprid and pH 3.0 for acetamiprid at the following measurement parameters: pulse amplitude 50 mV, pulse width 50 ms and scan rate 25 mV. Calibration curves were linear in the concentration range of 2.43 – 51.1 mg/cm 3 for imidacloprid and 2.95 – 47.3 mg/cm 3 for acetamiprid, while the detection limits were 0.73 mg/cm 3 and 0.88 mg/cm 3 for imidacloprid and acetamiprid, respectively. The electroanalytical method has allowed monitoring the heterogeneous photocatalytic (O2/TiO2/UV) degradation of the two insecticides via their disappearance. The dynamics and the reaction rate determined on the basis of the electrochemical data were validated with HPLC/DAD and FTIR measurements.

Monitoring of Photocatalytic Degradation of Selected Neonicotinoid Insecticides by Cathodic Voltammetry with a Bismuth Film Electrode

The voltammetry of imidacloprid was investigated by using three kinds of carbon paste electrodes (CPEs) based on tricresyl phosphate, silicone oil, and n-tetradecane. The tricresyl phosphate-based carbon paste electrode exhibited the best analytical performance with respect to peak shape and signal intensity. The method, operated in the differential pulse voltammetric mode, was applied to the determination of imidacloprid in a river water sample and two commercial formulations and works in the concentration range from 1.7 to 30 μg mL−1, with a relative standard deviation not exceeding 2.2%. This appears to be the first application of a CPE to the voltammetric determination of neonicotinoid insecticides.

Voltammetric determination of imidacloprid insecticide in selected samples using a carbon paste electrode

The influence of the pH on the persistence of four neonicotinoid insecticides: imidacloprid, thiamethoxam, acetamiprid and thiacloprid, was studied by 1 H NMR spectrometry at different pH values of Britton-Robinson buffers (4.0, 7.0 and 9.0) at a constant temeprature. Thiamethoxam and imidacloprid, having an identical nitroguanidine functional group, exhibited low persistence in alkaline media, as their degradation started already after three and five days, respectively. On the other hand, at pH 4.0 and 7.0 they remained unaffected for several months. In contrast to them, thiacloprid and acetamiprid, the compounds with a cyanoimine functional group, were less persistent in acidic solution. In alkaline media, they were stable for about 30 days. The proportion of hydrolyzed pesticide was calculated from the 1 H NMR spectra by comparing the integrals of compound signals with the signal of acetate standard.

NMR Study of the Influence of pH on the Persistence of Some Neonicotinoids in Water

We studied the analysis of trace amounts of neonicotinoid insecticides by liquid chromatography coupled with a thermal lens spectrometric detector (TLS). This multi-residue analysis method is based on the reversed phase separation on C18 column, isocratic elution and collinear dual beam TLS detection. The insecticides thiamethoxam, imidacloprid, acetamiprid and thiacloprid were detected with retention times of 4.4, 5.7, 6.5 and 8.5 min and limits of quantifications of 50, 89, 10, and 25 μg/L, respectively. The retention times agreed well with those obtained by the same chromatographic method but using a diode-array detector (DAD). The limits of quantifications for imidacloprid were identical in both techniques. However, the limits of quantifications for thiamethoxam, acetamiprid and thiacloprid were up to 8.5 times lower using the TLS detector compared to the diode-array detector. The applicability of the developed procedure was tested on spiked river water and potato samples.

Ferenc F. Gaál

Papers

Voltammetric determination of imidacloprid and thiamethoxam

Monitoring of Photocatalytic Degradation of Selected Neonicotinoid Insecticides by Cathodic Voltammetry with a Bismuth Film Electrode

Voltammetric determination of imidacloprid insecticide in selected samples using a carbon paste electrode

NMR Study of the Influence of pH on the Persistence of Some Neonicotinoids in Water

Determination of selected neonicotinoid insecticides by liquid chromatography with thermal lens spectrometric detection