Pesticides In Aqueous Solutions Research Articles

Hierarchical porous carbon with designed pore architecture and study of its adsorptive properties

Ordered mesoporous carbon nanoparticles have been synthesized by a nanocasting procedure from furfuryl alcohol impregnation into alumino–silica UVM-7 material. By a proper adjustment of the synthesis parameters, furfuryl alcohol volume vs. template pore volume, it was possible to obtain a carbonaceous templated material which keeps the hierarchical bimodal porosity of the silica together with its high surface area (>1000 m 2/g), as it was confirmed by means of electron transmission microscopy and N 2 adsorption isotherms. This carbon material was evaluated by testing it as a sorbent for several pesticides in aqueous solutions. Its absorption efficiency was compared with typical commercial solid phase extraction materials such as silica C 18 and graphitized carbon black GCB.

Luminescence switching of CdTe quantum dots in presence of p-sulfonatocalix[4]arene to detect pesticides in aqueous solution

A simple, rapid, and sensitive identification method of fenamithion and acetamiprid is developed using supramolecular nano-sensitizers combining of CdTe quantum dots (QDs) and p-sulfonatocalix[4]arene as additive by fluorescent spectroscopic technique in water. Depending on p-sulfonatocalix[4]arene, the selectivity of CdTe QDs is tuned between fenamithion and acetamiprid. The luminescence of free CdTe QDs is quenched selectively to fenamithion. While in the presence of p-sulfonatocalix[4]arene, it shows that the fluorescence intensity of QDs is enhanced selectively to acetamiprid due to the cooperation of QDs and p-sulfonatocalix[4]arene. Based on the response characteristics of the QDs, a fluorescent method is performed for tuning selective determination of the pesticides. Under optimum conditions described, it is found that the pesticides effect on the luminescence of the CdTe QDs in concentrations dependence are described by a Stern–Volmer-type equation or a Langmuir binding isotherm equation in the range of 0–10 −4 M (fenamithion) and 0–10 −3 M (acetamiprid), with the corresponding detection limits (3 σ) of 1.2 × 10 −8 M (fenamithion) and 3.4 × 10 −8 M (acetamiprid), respectively. The possible mechanism is discussed.

Electrocatalytic Detection of Amitrole on the Multi-Walled Carbon Nanotube - Iron (II) tetra-aminophthalocyanine Platform.

It is shown that iron(II) tetra-aminophthalocyanine complex electropolymerized onto a multi-walled carbon nanotube-modified basal plane pyrolytic graphite electrode greatly enhanced the electrocatalytic detetion of amitrole (a toxic herbicide), resulting in a very low detection limit (0.5 nM) and excellent sensitivity of 8.80±0.44 μA/nM, compared to any known work reported so far. The electrocatalytic detection of amitrole at this electrode occurred at less positive potential (∼0.3 V vs Ag|ACl) and also revealed a typical coupled chemical reaction. The mechanism for this response is proposed. The electrode gave satisfactory selectivity to amitrole in the presence of other potential interfering pesticides in aqueous solutions.

Evaluation of the Performance of Flow-through Anodic Fenton Treatment in Amide Compound Degradation

A flow-through anodic Fenton treatment (FAFT) system based on the batch AFT technology was previously developed to degrade pesticides in aqueous solution. As one of a series of benchtop and pilot-scale studies in process optimization, the goal of the reported work is to evaluate the performance of the FAFT system under various operating conditions, which is critical to bringing this technology into practical general use in the field. For this purpose, the removal efficiency of the parent pesticide and the concentration of the hydroxyl radical in FAFT were calculated on the basis of a previously developed FAFT kinetic model and used for the evaluation. N,N-Diethyl-3-methylbenzamide (DEET), an insect repellent, was used as a chemical probe. Experimental data showed that the key to a high treatment efficiency is to operate the FAFT system to achieve a maximum *OH production with a minimum input of energy and chemicals. For the anodic half-cell, the system should be operated under flow-through conditions with a self-developed optimum pH of 3.0, a relatively high flow rate, and the initial effluent recycled within 6-10 min to the FAFT system for further treatment; for the cathodic half-cell, it should have a fixed volume and be entirely replaced by another batch of cathodic solution only when the pH reaches a very high value. The delivery rate of the ferrous iron should be maintained at an electrolytic current between 0.01 and 0.02 A; the ratio of H2O2/Fe2+ should be between 5:1 and 10:1. NaCl was found to be the best electrolyte, with concentrations of 0.01-0.02 and 0.08 M in the anodic and cathodic half-cells, respectively. The FAFT system was successfully applied to degrade various model amide compounds and DEET formulations, which suggests the likelihood of extending this approach to other pesticide-containing wastewaters.

Reaction Mechanism and Kinetic Modeling of DEET Degradation by Flow-Through Anodic Fenton Treatment (FAFT)

The previously developed batch anodic Fenton treatment (AFT) technology has been successfully applied to degrade various pesticides in aqueous solution. The goal of this work is the development of a flow-through AFT system (FAFT) which is critical to bringing this technology into practical general use in the field. For this purpose, the degradation of DEET (N,N-diethyl-3-methylbenzamide), an insect repellent, and nine model amides was studied. Oxidation products of these compounds in FAFT were identified by GC/MS, and the results revealed that various -OH additions (most likely on the aromatic ring), quinone/keto product formation, and dimerization/bimolecular disproportionation are the major reaction pathways. This proposed overall reaction mechanism was then combined with the basic Fenton's mechanism to model the kinetics of various active species in FAFT including DEET, Fe2+, H2O2, and total iron under different reaction conditions. In addition, both initial and steady-state hydroxyl radical concentrations were measured in FAFT using benzoic acid as a chemical probe; the measured *OH concentrations were best-fitted exponentially. On the basis of the obtained [*OH] trend and the mass balance of the FAFT system, a simple FAFT model was developed to fit all of the degradation data of DEET and the model amides.

Photosensitized degradation of ethyl parathion pesticide in aqueous solution of anthracene modified photoactive dextran

The photosensitized oxidation of parathion-ethyl (PTE) pesticide in the aqueous solution of anthracene substituted dextran (DXA) was investigated. The phototransformation of PTE was found to be significantly enhanced in the presence of DXA. The suggested mechanisms of reactions involve photoinduced electron transfer process as a primary photophysical step. DXA polymer plays a role of environmentally friendly photosensitizer since after the reaction it undergoes decomposition.

A liquid‐phase microextraction method, combining a dual gauge microsyringe with a hollow fiber membrane, for the determination of organochlorine pesticides in aqueous solution by gas chromatography/ion trap mass spectrometry

A liquid-phase microextraction (LPME) method has been demonstrated for the extraction and determination of organochlorine pesticides (OCPs) in aqueous solution. The method combines a dual gauge microsyringe with a hollow fiber membrane (LPME/DGM-HF) followed by detection by gas chromatography/ion trap mass spectrometry (GC/ITMS). The advantages include speed, low solvent and sample consumption, simplicity and ease of use. The extraction time, solvent selection, salt concentration and sample stirring rate have been investigated in order to optimize extraction efficiency. The viability is evaluated by measuring the linearity and detection limit of the five OCPs in aqueous solution. Detection linearity for the OCPs has been achieved over a range of concentrations between 1 and 500 microg/L (r2 > 0.930), with a detection limit of 0.1 microg/L for each OCP.

Sol–gel based mid-infrared evanescent wave sensors for detection of organophosphate pesticides in aqueous solution

This work demonstrates the application of organically modified sol–gels as recognition layers combined with mid-infrared evanescent wave sensors for in situ detection of nitrated organics in aqueous media. Sol–gels were prepared by acid-catalyzed copolymerization of phenyltrimethoxysilane (PTMOS) and tetramethoxysilane (TMOS) and were spin-coated onto ZnSe attenuated total reflection (ATR) waveguides. These sensors were investigated with respect to their enrichment properties of selected organophosphates, i.e. parathion, fenitrothion and paraoxon, respectively, and their capability of suppressing interfering water background absorptions. Figures of merit are derived from calibration curves determined to assess sensitivity and reproducibility of the applied sensor system. It can be concluded that sol–gel coated infrared optical sensors enable reproducible detection of organophosphates down to the sub-ppm concentration range. Furthermore, measurement of spiked river water samples demonstrates feasibility as remote field sensor system. Once the required sensitivity is achieved, sol–gel based mid-infrared evanescent wave sensors have the potential of being an alternative to commonly applied biosensors for detection of organophosphates in environmental analysis, since they provide superior mechanical and chemical stability during application relevant periods of time.

Direct phototransformation of aromatic pesticides in aqueous solution

The photochemical behaviour of many aromatic pesticides (mainly herbicides) are compared and the main reactions are separated in three different classes: 1‐ reactions involving carbon‐halogen bond; 2 ‐ other reactions involving the aromatic ring; 3 ‐ reactions of the aliphatic moiety. It appears that the nature of the substituents and their relative positions on the ring play a major role in the orientation of the reaction. The molecular and ionic forms of ionisable molecules may have different photochemical behaviour. A wavelength effect is observed with some compounds. The case of mecoprop [2‐(4‐chloro‐2‐methylphenoxy)‐propanoic acid] is presented as an example.The irradiation of herbicides in aqueous solution may lead to the formation of photochemical intermediates more toxic to microorganisms than the initial substrate.

Degradation of some pesticides in aqueous solutions by electron beam and gamma-radiation

Decomposition by ionizing radiations of two pesticides (Lannate and Fenvalerate) present in an aqueous solution has been studied on laboratory-scale experiments. The effect of pH of the solution, the concentration of the pesticide and the irradiation dose on the degradation process was investigated. Gamma-irradiation was carried out in air and in combination with nitrogen, oxygen and ozone. Lannate showed more degradation than Fenvalerate in all conditions investigated. Radiation was not enough to achieve the complete decomposition of the pesticides. Adsorption of the pollutants after irradiation was achieved using granular activated carbon (GAC) and two anion exchangers (Dowex 1-X8 and Lewatit AP 246).

Determination photostability of selected agrochemicals in water and soil

The photolysis of selected pesticides in aqueous solutions has been investigated. The photolysis produced different intermediate substances, which were also found to be soil and microbial degradation products The phototransformation in the presence of TiO 2 and humic substances leads to a disappearance of these compounds The reaction rate is dependent on the semiconductor oxide and concentration. Photoproducts were isolated and characterized by different spectroscopic methods. Results from this study indicate that degradation products of isoproturon are more toxic on Daphnia magna than on the parent compound.

Photodecomposition of the Carbamate Pesticide Carbofuran: Kinetics and the Influence of Dissolved Organic Matter

This study examined the photodecomposition of carbofuran, a carbamate pesticide with high oral toxicity. Rate constants are measured for the pesticide in aqueous solution and in the presence of various samples of dissolved organic matter (DOM). Kinetic experiments are monitored with HPLC, while reaction products are determined using HPLC, GC−MS, and 1H NMR: mechanisms are proposed for the first three steps of the reaction. It was found that the photodecomposition proceeds via first-order reaction kinetics and that the presence of various DOM samples inhibits the photolysis reaction of carbofuran. This phenomenon can be correlated to the magnitude of the binding interaction between carbofuran and DOM. Finally, techniques such as GC−MS and 1H NMR are used to identify the photodecomposition products. The first three steps of the reaction are defined. In the first step of the reaction, the carbamate group is cleaved from the molecule. The furan moiety is opened in the second step producing a substituted catechol with a tert-butyl alcohol group as the substituent at the number three carbon. This molecule then undergoes a dehydration reaction to form an alkene side group from the tert-butyl alcohol side group.

Surface plasmon resonance sensor for pesticide detection

Abstract The optoelectronic biosensor, based on surface plasmon resonance (SPR) for detection of photosynthesis-inhibiting pesticides in aqueous solutions was presented. The pesticide capability to replace plastoquinone from its complex with D1 protein was used for the detection. This replacement reaction results in the changes of the optical characteristics of protein layer, immobilized on the gold surface. Monitoring of these changes with SPR-technique permits to determine 0.05–5.0 μg/ml pesticide in solution within 1 h.

Comparative study on the quantum yields of direct photolysis of organophosphorus pesticides in aqueous solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComparative study on the quantum yields of direct photolysis of organophosphorus pesticides in aqueous solutionHai Bin Wan, Ming Keong Wong, and Chup Yew MokCite this: J. Agric. Food Chem. 1994, 42, 11, 2625–2630Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/jf00047a046RIGHTS & PERMISSIONSArticle Views572Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (690 KB) Get e-Alerts Get e-Alerts

Aqueous Ozonation of Pesticides: A Review

Abstract The ozonation reactions of pesticides in aqueous solution have been reviewed. Degree of reaction and reaction product identity are included. Compounds are classified into five groups: chlorinated hydrocarbons, organophosphorus compounds, phenoxyalkyl acid derivatives, organonitrogen compounds, and phenolic compounds. Experimental conditions for each study are summarized. Much work has been carried out under conditions atypical of those encountered at drinking water treatment plants. Thus, the findings of the papers reviewed cannot be applied directly to potable water treatment.

Oxygen-flask combustion of accumulated organophosphorus pesticides for monitoring water pollution

A procedure is described for the determination of the total concentration of organophosphorus pesticides in aqueous solution based on conversion of the compounds to orthophosphoric acid by oxygen-flask combustion and spectrophotometric determination as phosphomolybdenum blue. The procedure is particularly sensitive when preceded by efficient and selective accumulation of pesticides. The adsorption of malathion, parathion and phosalone on Amberlite XAD-4 resin from 1 l of 7–36 μM water solutions, followed by combustion of 500 μl of eluate yields of orthophosphoric acid with 90–105% recoveries. The detection limit is ca. 150 ng ml −1 pesticide in an aqueous sample. Inorganic phosphates and most of some commonly present non-pesticide phosphorus compounds are eliminated from the water sample during the adsorption step. In combination with a test for monitoring traces of cholinesterase inhibitors in surface waters, the determination of the total amount of organophosphorus pesticides as a cumulative parameter offers reliable information on the pollution level of the water environment. Application of such a combined procedure to a pond water from an apple orchard showed good correlation between phosphrus content and the cholinesterase inhibition.

A test for monitoring traces of cholinesterase inhibitors in surface waters

The inhibitory effect on cholinesterase activity is the only common attribute of organophosphorus pesticides and carbamates. Therefore a screening test based on cholinesterase assay is suitable for detection of total pesticides in the pollution control of surface waters. The reaction-rate cholinesterase assay in which acetylthiocholine iodide is used as substrate and 5,5′-dithio-bis (2-nitrobenzoic acid) (Ellman's reagent) as indicator, with spectrophotometric monitoring at 412 nm for 2 min is applied. The detection limits for various pesticides in aqueous solutions have been determined. The results are comparable to those of gas Chromatographic analyses and for carbamates are even better. The sensitivity can be improved by two orders of magnitude by preconcentration on Amberlite XAD-4 column. The collection efficiency of about 80% for all the pesticides tested has been confirmed by gas chromatography. A rapid and simple field test is based on the same assay system. The reaction is stopped by complete inhibition of the enzyme and the colour is compared visually with that of standards prepared by dilution of the initial enzyme solution, and the comparison is facilitated by use of a red filter (λmax 555 nm). A relative standard deviation of 5.5% was obtained for 3 series of sample covering the range 0–100% inhibition, 9 experiments done by 6 persons.

Determination of Pesticides by Electron Capture Gas Chromatography

Methods for the removal of trace organic pollutants are being studied, but the applicability of these methods depends on the development of procedures for the analysis of pesticides in aqueous solution. A procedure for making this analysis by electron capture gas chromatography is described in this article.