Photodegradation Of Pesticides Research Articles

Recyclable NiO/g-C3N4/ag hybrid substrates for sensitive SERS detection and photo-degradation of residual pesticides in beverages

In this research, we fabricated an innovative NiO/CN/Ag composite through the straightforward electrostatic assembly of Ag nanoparticles and g-C3N4 sheets onto NiO nanoflowers. This composite enables both surface enhanced Raman spectroscopy (SERS) detection and photo-degradation of pesticides. The results reveal NiO/CN/Ag can quantitatively detect thiram (TRM) and diquat dibromide (DQDB) in water, with a limit of detection (LOD) of 10−9 M, and also exhibit outstanding photo-degradation efficiency, exceeding 95 % for TRM and DQDB within 90 min under simulated sunlight. Significantly, after the organic reagent (citric acid) on NiO/CN/Ag was completely removed through simulated solar irradiation, the signal-to-noise ratios of SERS spectra on NiO/CN/Ag were enhanced, achieving LODs of 10−8 M for TRM and DQDB in different fruit juices and dried flower teas. Additionally, the composite demonstrate impressive recyclability, maintaining robust SERS signals and high degradation rates even after five cycles of “detection-degradation” processes.

Spherical magnetic MgO-CeO2-Fe3O4@JB heterojunction for enhanced photodegradation of pesticide and complex anionic dyes: Understanding the degradation process and diverse water systems

Clothianidin (CLO) is a widely utilized pesticide recognized as an emerging pollutant capable of contaminating surface and subsurface water sources. Utilizing nanoparticles for photodegradation is a very ecological and cost-effective method for water treatment. This study involves the creation of a MgO-CeO2-Fe3O4@JB (Jute-Biochar) heterojunction with a mesoporous structure using hydrothermal process. The purpose of this design is to explore its potential for photocatalytic applications. PXRD (Powder X-ray Diffraction), FTIR (Fourier Transform Infrared), UV–DRS (Ultraviolet–Visible Diffuse Reflectance Spectroscopy), PL (Photoluminescence), TEM (Transmission Electron Microscopy), EDX (Energy Dispersive X-ray), XPS (X-ray Photoelectron Spectroscopy), VSM (Vibrating Sample Magnetometry), BET (Brunauer Emmett Teller), and SEM (Scanning Electron Microscopy) analysis confirmed the formation of a mesoporous MgO-CeO2-Fe3O4@JB heterojunction with preferred interface between MgO, CeO2, and Fe3O4 phases, extending the light-absorption insights to 700 nm. The photocatalytic performance of MgO-CeO2-Fe3O4@JB heterojunction was evaluated under visible-light using CLO as the target molecule. The degradation performances of CLO on MgO-CeO2-Fe3O4@JB were determined to be 95.24 ± 1.18 % after 35 min of exposure to light. The calculated rate constants for the degradation of CLO in presence of light using the MgO-CeO2-Fe3O4@JB composite were determined to be 0.0924 min−1. Furthermore, two complex dyes, Niagara Blue (NB) and Reactive Red (RR), photodegrade to 99.45 ± 1.24 % and 97.23 ± 1.41 % within 25 and 30 min, respectively. The excellent photocatalytic characteristics of the MgO-CeO2-Fe3O4@JB heterojunction were suggested to be primarily caused by the larger photo-response, aligned band-structure, and useful use of the photo-induced charge carriers of the photocatalyst. In addition, the recycling experiments have verified the exceptional photostability of the MgO-CeO2-Fe3O4@JB photocatalyst due to incorporation of nanoparticles into the biochar matrix. This leads to a synergistic mechanism for effectively eliminating these pollutants.

Efficient construction of self-assembled starch colloidosomes for controlled-release of pesticides

Biodegradable colloidosomes have attracted increasing attention for their applications to enhance the efficacy and reduce wastage of pesticides in agriculture. In this study, we present a continuous and highly efficient method for production of starch colloidosomes. The starch particles with an average particle size of 230.2 nm and good dispersibility were prepared using surface modification technology, and then used as environment-friendly shell materials to form self-assembled starch colloidosomes using spray drying technology. The influences of inlet temperature, feed rate and air flow rate on the morphologies of colloidosomes were also studied. This strategy enables the construction of starch colloidosomes with uniform spherical morphology and controllable pore sizes under different pH, and can be used for pesticide encapsulation. After loading pyraclostrobin (PYR), the regular spherical colloidosomes not only achieve a small mean diameter of 2.35 µm, but also realize a high encapsulation efficiency of 82 %. The release performance of PYR has an obvious pH response and follows the segmented Ritger-Pepapes model of sustained-release. The colloidosomes were used to prevent the photodegradation of pesticides. The PYR loaded colloidosomes exhibit excellent UV resistance with a retention rate of 72.7 %. In addition, the loading of Fe3O4 nanoparticles and the embedding of carbon dots were also explored.

Application of machine learning models to improve the prediction of pesticide photodegradation in water by ZnO-based photocatalysts

Pesticide pollution has been posing a significant risk to human and ecosystems, and photocatalysis is widely applied for the degradation of pesticides. Machine learning (ML) emerges as a powerful method for modeling complex water treatment processes. For the first time, this study developed novel ML models that improved the estimation of the photocatalytic degradation of various pesticides using ZnO-based photocatalysts. The input parameters encompassed the source of light, mass proportion of dopants to Zn, initial pesticide concentration (C0), pH of the solution, catalyst dosage and irradiation time. Additionally, physicochemical properties such as the molecular weight of the dopants and pesticides, as well as the water solubility of both dopants and pesticides, were considered. Notably, the numerical data were extracted from the literature via relevant tables (directly) or graphs (indirectly) using the web-based tool WebPlotDigitizer. Four ML models including multi-layer perceptron artificial neural network (MLP-ANN), particle swarm optimization-adaptive neuro fuzzy inference system (PSO-ANFIS), radial basis function (RBF), and coupled simulated annealing-least squares support vector machine (CSA-LSSVM) were developed. In comparison, RBF showed the best accuracy of modeling among all models, with the highest determination coefficient (R2) of 0.978 and average absolute relative deviation (AARD) of 4.80%. RBF model was effective in estimating the photocatalytic degradation of pesticides except for 2-chlorophenol, triclopyr and lambda-cyhalothrin, where CSA-LSSVM model demonstrated superior performance. Dichlorvos was completely degraded by ZnO photocatalyst under visible light. The sensitivity analysis by relevancy factor exhibited that light irradiation time and initial pesticide concentration were the most important parameters influencing photocatalytic degradation of pesticides positively and negatively, respectively. The new ML models provide a powerful tool for predicting pesticide degradation in wastewater treatment, which will reduce photochemical experiments and promote sustainable development.

Efficient visible light-driven photodegradation of glyphosate utilizing Bi2WO6 with oxygen vacancies: Performance, mechanism, and toxicity assessment

Global environmental deterioration poses a major risk to ecological security and human health, and emerging technologies are urgently needed to deal with it. Therefore, the exploitation of photocatalysts with favorable activity for efficient degradation of pesticide contaminants is one of the strategies to achieve environmental remediation. Herein, oxygen vacancy-rich Bi2WO6 (Ov-BWO) was prepared through a solvothermal method utilizing ethylene glycol (EG), which exhibited excellent photocatalytic efficiency in photodegradation of glyphosate. The formation of oxygen vacancies (Ovs) in Ov-BWO was demonstrated utilizing XPS and EPR. PL, TRPL, photocurrent tests, and EIS analyses revealed that Ovs accelerated effective transfer of photogenerated charge, extended lifetime of charge carriers, promoted production of active species and significantly improved the photocatalytic performance. Compared with the low-activity Bi2WO6 (BWO, 59.6%), Ov-BWO showed outstanding photocatalytic activity, achieving a degradation efficiency of 91% for glyphosate at 120 min of visible light irradiation. Moreover, Ov-BWO also displayed outstanding recyclable stability after four repeated uses. Based on the characterization of photoelectric properties, a feasible photocatalytic reaction was put forth, along with glyphosate degradation pathways. Furthermore, the degradation intermediates of glyphosate were analyzed in detail employing HPLC-MS. The toxicity assessment indicated that degraded products had been proven to be non-toxic to the ecological system. This work presents the potential of photocatalysts with Ovs for the photodegradation of pesticides, providing a viable strategy for environmental renovation.

Degradation of Pesticides Using Semiconducting and Tetrapyrrolic Macrocyclic Photocatalysts-A Concise Review.

Exposure to pesticides is inevitable in modern times, and their environmental presence is strongly associated to the development of various malignancies. This challenge has prompted an increased interest in finding more sustainable ways of degrading pesticides. Advanced oxidation processes in particular appear as highly advantageous, due to their ability of selectively removing chemical entities form wastewaters. This review provides a concise introduction to the mechanisms of photochemical advanced oxidation processes with an objective perspective, followed by a succinct literature review on the photodegradation of pesticides utilizing metal oxide-based semiconductors as photosensitizing catalysts. The selection of reports discussed here is based on relevance and impact, which are recognized globally, ensuring rigorous scrutiny. Finally, this literature review explores the use of tetrapyrrolic macrocyclic photosensitizers in pesticide photodegradation, analyzing their benefits and limitations and providing insights into future directions.

Preparation of mesoporous Hangjin 2# clay supported Nd-TiO2 and its photodegradation of organophosphorus pesticides wastewater

Hangjin 2# clay exhibits excellent adsorption properties and stability, which has been extensively used in many fields. It was further modified into mesoporous clay (MC) to enhance its degradation performance. Nd-TiO2/MC catalysts were synthesized through high-energy ball milling. The results were characterized using various techniques such as XRD, HRTEM, SEM, N2 adsorption-desorption, XPS, UV-Vis DRS, and photo electrochemistry. The photocatalytic degradation of the organic pesticide monocrotophos (Mcp) was tested. The findings revealed that the addition of Nd could induce lattice distortion in TiO2, reduce the bandgap, decrease grain size, and increase the specific surface area. Among these catalysts, 0.5 mol% Nd-TiO2 exhibited the most effective photodegradation performance. At 0.5 mol% Nd, the photocurrent was enhanced, charge transfer resistance was reduced, e-/h+ recombination was effectively inhibited, and the lifetime of e-/h+ pairs was extended. With the addition of 2.5 mg of the catalyst and 1.5 h of irradiation under a 400 W gold halide lamp, only 8.89% of Mcp remained. After loading onto MC, the photodegradation performance of 0.5 mol% Nd-TiO2/MC (30%) was the most remarkable. Under the same conditions, the active component was 2.3 mg, leading to complete degradation of Mcp. Additionally, the mesoporous clay could adsorb the ions produced during the degradation process. This study utilizes rare earth Nd-doped titanium dioxide for the photodegradation of Mcp, with Hangjin 2# clay selected for loading, offering a novel approach to pesticide photodegradation.

Solar-assisted photodegradation of pesticides over pellet-shaped TiO2-kaolin catalytic macrocomposites at semi-pilot-plant scale: Elucidation of photo-mechanisms and water matrix effect

The behavior of novel pellet-shaped bulky titania-kaolin photocatalysts is herein evaluated for its application in the solar-assisted photocatalytic treatment of a bio-recalcitrant pesticide mix (imidacloprid, pyrimethanil and methomyl) in solar lab-scale and semi-pilot scale raceway pond photoreactors. The photocatalyst consists of 1 cm long titania-kaolin macro-composites that combine some advantages of both nanoparticulate and supported catalysts without being either. This opening the opportunity to extend the use of this photocatalyst to complex wastewater effluents. In addition, their stability and reusability potential was also evaluated, and reactive species leading to the solar-degradation of each pesticide were also identified using radical scavengers. Total removal of pesticides (2 mg L−1 each) with an optimal pellets dosage of 34.8 g L−1 was addressed, whether in ultrapure water (180–270 min of solar irradiation) or in two basic pH Municipal Wastewater Treatment Plant (MWWTP) effluents (≤300 min of solar irradiation) where methomyl was always the most recalcitrant pesticide. Lower Total Organic Carbon (TOC) removal (≈53–56%) was also found under the effect of these complex MWWTP effluents than in ultrapure water (>60%). Those results are very promising when comparing to the almost negligible TOC removal achieved with the Titania powder under basic MWWTP effluents due to the strong effect of particle aggregation. Very good photocatalyst stability and durability was shown along three consecutive cycles after applying a low-cost recovery protocol consisting of several washing and drying cycles without addressing a significant photoefficiency loss (TOC≈60-56%). The application of scavengers revealed that hydroxyl radical generated from photoinduced holes was the dominant species in the degradation of pyrimethanil and methomyl whereas reactive oxygen species formed from conduction band electrons were mainly involved in the photo-oxidation of imidacloprid.

A Brief Review of Photocatalytic Reactors Used for Persistent Pesticides Degradation

Pesticide pollution is a major issue, given their intensive use in the 20th century, which led to their accumulation in the environment. At the international level, strict regulations are imposed on the use of pesticides, simultaneously with the increasing interest of researchers from all over the world to find methods of neutralizing them. Photocatalytic degradation is an intensively studied method to be applied for the degradation of pesticides, especially through the use of solar energy. The mechanisms of photocatalysis are studied and implemented in pilot and semi-pilot installations on experimental platforms, in order to be able to make this method more efficient and to identify the equipment that can achieve the photodegradation of pesticides with the highest possible yields. This paper proposes a brief review of the impact of pesticides on the environment and some techniques for their degradation, with the main emphasis on different photoreactor configurations, using slurry or immobilized photocatalysts. This review highlights the efforts of researchers to harmonize the main elements of photocatalysis: choice of the photocatalyst, and the way of photocatalyst integration within photoreaction configuration, in order to make the transfer of momentum, mass, and energy as efficient as possible for optimal excitation of the photocatalyst.

Surface-initiated polymerization of PVDF membrane using amine and bismuth tungstate (BWO) modified MIL-100(Fe) nanofillers for pesticide photodegradation.

Pirimicarb as a pesticide is used to control the aphids in the agriculture field; however, it affects the groundwater ecosystem by leaching through the soil profile. The post-synthetic amine and BWO modified MIL-100 (Fe) nanofillers were synthesized. The photocatalytic property of amine-functionalized and BWO@MIL-100(Fe) nanofillers was confirmed by the lesser bandgap energy than the unmodified MIL-100 (Fe) nanofiller. Herein, we constructed a nanofillers grafted PVDF membrane via in-situ polymerization technique for the pirimicarb reduction and photodegradation. Furthermore, the nanofiller's grafted membranes were characterized by FESEM, XRD, FTIR, and contact angle analysis. The carboxylic acid peak was observed on the FTIR which demonstrated the PAA grafted on the membrane surface and similar crystalline peaks evident that the nanofillers were grafted on the membrane surface. Furthermore, surface morphology studies have exhibited the dispersion of nanofillers and enhanced microvoids in the cross-section of the membrane. The decrease in the water contact angle of the membrane depicted the improved antifouling properties and surface energy. The nanofiller's grafted membranes have shown higher hydrophilicity correlated well with the enhanced pure water flux in the order M4>M5>M2>M3>M6>M7 compared to the neat membrane (M1). In BWO@MIL-100(Fe) membrane has shown a higher permeate flux (25.99Lm-2.h-1) than the neat PVDF membrane. The BWO@MIL-100(Fe) grafted PVDF membrane has also shown excellent pirimicarb photodegradation of 81% at pH 5. The proposed MIL-100 (Fe) and bismuth tungsten nanocomposite will pave the way for the different MOF-based photocatalytic materials for membrane-based pesticide degradation.

Challenges and effectiveness of nanotechnology-based photocatalysis for pesticides-contaminated water: A review

Pesticides have been frequently used in agricultural fields. Due to the expeditious utilization of pesticides, their excessive usage has negative impacts on the natural environment and human health. This review discusses the successful implications of nanotechnology-based photocatalysis for the removal of environmental pesticide contaminants. Notably, various nanomaterials, including TiO2, ZnO, Fe2O3, nanoscale zero-valent iron, nanocomposite-based materials, have been proposed and have played a progressively essential role in wastewater treatment. In addition, a detailed review of the crucial reaction condition factors, including water matrix, pH, light source, temperature, flow rate (retention time), initial concentration of pesticides, a dosage of photocatalyst, and radical scavengers, is also highlighted. Additionally, the degradation pathway of pesticide mineralization is also elucidated. Finally, the challenges of technologies and the future of nanotechnology-based photocatalysis toward the photo-degradation of pesticides are thoroughly discussed. It is expected that those innovative extraordinary photocatalysts will significantly enhance the performance of pesticides degradation in the coming years.

Environmental photochemistry on plants: recent advances and new opportunities for interdisciplinary research.

Plants play a central role in the photochemistry of chemicals in the environment. They represent a major atmospheric source of volatile organic compounds (VOCs) but also an important environmental surface for the deposition and photochemical reactions of pesticides, gaseous and particulate pollutants. In this review, we point out the role of plant leaves in these processes, as a support affecting the reactions physically and chemically and as a partner through the release of natural constituents (water, secondary metabolites). We discuss the influence of the chosen support (leaves, needle surfaces or fruit cuticles, extracted cuticular waxes and model surfaces) and other factors (additives, pesticides mixture, and secondary metabolites) on the photochemical degradation kinetics and mechanisms. We also show how plants can be a source of photochemically reactive species which can act as photosensitizers promoting the photodegradation of pesticides or the formation and aging of secondary organic aerosols (SOA) and secondary organic materials (SOM). Understanding the fate of chemicals on plants is a research area located at the interface between photochemistry, analytical chemistry, atmospheric chemistry, microbiology and vegetal physiology. Pluridisciplinary approaches are needed to deeply understand these complex phenomena in a comprehensive way. To overcome this challenge, we summarize future research directions which have been clearly overlooked until now.

Eco-friendly mechanochemical synthesis of titania-graphene nanocomposites for pesticide photodegradation

Titania graphene hybrid nanocomposites (TiO2-FLG) synthesized from graphite and TiO2 precursors, in a simple and sustainable approach via a three-step method, including the mechanochemical treatment of pre-synthesized FLG and TiO2 NPs are efficient has led to the preparation of TiO2-FLG as efficient nano-catalysts for photocatalytic degradation of a complex mixing of pesticides (isoproturon, pyrimethanil, alachlor and methomyl). The effect of few layer graphene (FLG) loading (0–1.0%) was analyzed to define the optimal ratio of FLG to TiO2 and compared with the corresponding physical mixtures. X-ray Powder Diffraction (XRD) patterns of all these hybrid photocatalysts have presented the same crystal structure, with anatase as the main crystalline phase and brookite as secondary phase. An interaction between the graphene structure and the TiO2 nanoparticles has been observed from Energy Dispersive X-Ray (EDX), X-ray photoelectron (XPS) and Raman spectroscopy studies, indicating that FLG is mainly deposited on the surface wrapping the TiO2 nanoparticles. The presence of FLG in low concentrations and the mechanochemical activation are the key steps to improve the photocatalytic activity of TiO2 nanoparticles on these hybrid nanocomposites. The TiO2-FLG-0.5% hybrid nanocomposite, with circa 1.9 % content of graphitic carbon in surface, has showed the best photocatalytic performance in the degradation of pesticides. Pesticides were completely removed at 350 min, and around 82 % of total organic carbon (TOC) conversion was achieved at 540 min of irradiation time.

Photochemical interactions between pesticides and plant volatiles

Among the numerous studies devoted to the photodegradation of pesticides, very scarce are those investigating the effect of plant volatiles. Yet, pesticides can be in contact with plant volatiles after having been spread on crops or when they are transported in surface water, making interactions between the two kinds of chemicals possible. The objectives of the present study were to investigate the reactions occurring on plants. We selected thyme as a plant because it is used in green roofs and two pesticides: the fungicide chlorothalonil for its very oxidant excited state and the insecticide imidacloprid for its ability to release the radical NO2 under irradiation. Pesticides were irradiated with simulated solar light first in a solvent ensuring a high solubility of pesticides and plant volatiles, and then directly on thyme's leaves. Analyses were conducted by headspace gas chromatography–mass spectrometry (HS-GC–MS), GC–MS and liquid chromatography-high resolution mass spectrometry (LC-HRMS). In acetonitrile, chlorothalonil photosensitized the degradation of thymol, α-pinene, 3-carene and linalool with high quantum yields ranging from 0.35 to 0.04, and was photoreduced, while thymol underwent oxidation, chlorination and dimerization. On thyme's leave, chlorothalonil was photoreduced again and products arising from oxidation and dimerization of thymol were detected. Imidacloprid photooxidized and photonitrated thymol in acetonitrile, converting it into chemicals of particular concern. Some of these chemicals were also found when imidacloprid was irradiated dispersed on thyme's leaves. These results show that photochemical reactions between pesticides and the plants secondary metabolites can take place in solution as on plants. These findings demonstrate the importance to increase our knowledge on these complex scenarios that concern all the environmental compartments.

Pilot-scale direct UV-C photodegradation of pesticides in groundwater and recycled wastewater for agricultural use

Pesticides widely used for intensive agriculture may leach to groundwater and pose problems to drinking water and irrigation. UV-C disinfection systems (UV-DS) for water disinfection can be used also for the abatement of organic micropollutants. A pilot-scale continuous flow-through UV-DS system was evaluated for its degradation efficiency of atrazine (ATR), malathion (MAL) and glyphosate (GLY) from 40 L water. Groundwater used to irrigate potato fields and recycled wastewater used to wash potatoes were treated without catalysts to avoid any toxicity effect on potatoes. Chromatographic methods were used to quantify very low pesticide levels before and after UV-C treatments (<10 µg L−1), while a specific method was adapted to analyse traces of GLY (0.0008–10 µg L−1) in recycled wastewater containing suspended particulate matter (SPM). ATR was completely eliminated from groundwater after 15 min photodegradation while 80% was removed from the turbid wastewater after 25 min. For MAL, 70–80% was removed in 25 min from the groundwater. For wastewater, the initial concentration was important for the performance of the photolytic process. An amount of 75% of GLY was eliminated after 10 min irradiation at concentrations higher than those found in natural groundwater. In wastewater, the UV-C treatment was less efficient because GLY was mainly adsorbed to SPM which obstruct the photodegradation process. Therefore, the pilot-scale UV-DS using a turbulent flow and a multiple-lamp system was performed to remove quantitatively traces of pesticides from large volumes of water, by direct photolytic oxidation, when the turbidity of the treated water was limited.

Photocatalytic Degradation of Diazinon with a 2D/3D Nanocomposite of Black Phosphorus/Metal Organic Framework

Metal–organic frameworks (MOFs) are promising materials for the removal and photodegradation of pesticides in water. Characteristics such as large surface area, crystalline structure and catalytic properties give MOFs an advantage over other traditional adsorbents. The application of MOFs in environmental remediation is hindered by their ability to only absorb in the UV region. Therefore, combining them with an excellent charge carrier 2D material such as black phosphorus (BP) provides an attractive composite for visible-light-driven degradation of pesticides. In the study, a nanocomposite of black phosphorus and MIL-125(Ti), defined as BpMIL, was prepared using a two-stage hydrothermal and sonication route. The as-prepared composite was characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. These techniques revealed that the circular and sheet-like morphology of the nanocomposites had minimum charge recombination, allowing them to be effective photocatalysts. Furthermore, the photocatalysts exhibited extended productive utilization of the solar spectrum with inhibited recombination rate and could be applied in visible-light-driven water treatment. The photodegradation of diazinon in water was studied using a series of BpMIL (4%, 6% and 12% by mass) nanocomposites as a photocatalyst. The optimal composite was determined to be 4%BpMIL. The degradation parameters were optimized and these included photocatalyst dosage, initial diazinon concentration and pH of the solution. The optimal conditions for the removal and degradation of diazinon were: neutral pH, [diazinon] = 20 mg/L, photocatalyst dosage = 0.5 g/L, achieving 96% removal of the pesticide after 30 min with 4%BpMIL, while MIL-125(Ti) showed 40% removal. The improved photodegradation efficiency of the 4%BpMIL composite was attributed to Ti3+-Ti4+ intervalence electron transfer and the synergistic effect between MIL-125(Ti) and BP. The photodegradation followed pseudo-first-order kinetics with a rate constant of 1.6 × 10−2 min−1.

Green synthesis of sunlight responsive zinc oxide coupled cadmium sulfide nanostructures for efficient photodegradation of pesticides

Structural design of semiconductor nanomaterials via facile and green methodology is noteworthy to advance their photocatalytic activity for resolving the problem of energy and environment. Herein, sunlight active zinc oxide coupled with cadmium sulfide (ZnO@CdS) was synthesized by employing the leaf extract of Azadirachta indica. Subsequently, it was used for removal of chlorpyrifos (CP) and atrazine (Atz) pesticides that have shown high persistence, bioaccumulation, and toxicity in the environment. Synthesized ZnO@CdS nanocomposite was characterized by spectroscopic and microscopic techniques. The unique morphology of nanocomposite (particle size ≤ 50 nm) and appearance of stretching vibrations at 600 cm−1 for Zn-S and 679 cm−1 for Cd-O has confirmed the coupling of ZnO with CdS. The degradation conditions were optimized by varying the pesticide amounts, catalyst dose, and pH under the sunlight irradiation. At moderate dosage and neutral pH, the nanocomposite was found highly efficient for the quantitative removal of pesticides (89–91%) due to improved surface area (111 m2g−1), low band energy (1.67 eV), and semiconducting nature resulted from synergism. The degradation followed Langmuir adsorption and first order kinetics. The Effect of ionic strength was helpful to understand the interaction mechanism involved in the removal of contaminants. Being more effective than natives, ZnO@CdS has substantially suppressed the half-life of pesticides as revealed from generation of smaller and less toxic metabolites in GC–MS analysis. The charge separation was supported by photoluminescence and UV-reflectance studies. A scavenger analysis has indicated the presence of active radicals in photocatalysis. The Applicability of green or alternative photocatalyst for multiple times (n = 10) confirmed its sustainability and high efficiency for environmental and industrial purposes.

Effect of main inorganic metal elements in Panax ginseng field soil on the photodegradation of fluazifop-p-butyl.

The widespread use of pesticides contributes to their existence in the environment. The compounds with photocatalytic activity in environmental matrixes play a significant effect on the photodegradation of pesticides. In order to clear the photolysis effects of the main characteristic inorganic metal elements in the of Panax ginseng field soil on fluazifop-p-butyl, a series of tests were carried out. The obtained results indicated that Mn2+ and Sn+ exhibited a significant photosensitization on the ultraviolet photodegradation of fluazifop-p-butyl. Also the high content of VO3- and Mo7O246- in the photolysis system showed a photoquenching on fluazifop-p-butyl, but the low content is a photosensitive effect. However, in the photolysis system, as the concentration of Co2+ and Li+ increases, the photoquenching effect on fluazifop-p-butyl becomes obvious, and no photosensitization at any tested concentration of them.

Palladium and silver nanoparticles embedded on zinc oxide nanostars for photocatalytic degradation of pesticides and herbicides

In this study, we demonstrated the efficient charge separation and migration at zinc oxide nanostars (ZnONSt) via conjugation with noble metal nanoparticle (MNP = Ag, Pd) and its application in degradation of carcinogenic pesticide [methyl parathion (MP)] and herbicides [pendimethalin (PDM), trifluralin (TFL)]. A well dispersed noble MNP incorporation on ZnONSt surface has been carried out by microwave-hydrothermal (MW-HT) method. The related phase constitution, the presence of functional groups, optical properties, elemental composition, surface area, and surface morphology were evaluated using various analytical techniques. The XRD patterns and FE-SEM/TEM micrographs revealed the ZnONSt had hexagonal wurtzite phase with a star-like morphology. The Ag@ZnONSt and Pd@ZnONSt exhibited excellent photocatalytic activity towards the photodegradation of pesticide, and herbicides under irradiation of visible light (VL). Pd and Ag nanoparticles act as electron sink and thus facilitate the interfacial charge transfer process by suppression of charge recombination rate. In particular, Pd@ZnONSt nanocomposite showed the better performance than the ZnONSt with different morphology and other commercial photocatalysts. A plausible mechanism for the enhanced photocatalytic activity by Pd@ZnONSt was proposed. Our results might open up a promising way to develop novel and highly efficient photocatalysts based on ZnONSt-related heterostructure.

Direct and indirect photodegradation of atrazine and S-metolachlor in agriculturally impacted surface water and associated C and N isotope fractionation.

Knowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters. Here, we investigated carbon (C) and nitrogen (N) isotope fractionation during direct and indirect photodegradation of the herbicides atrazine and S-metolachlor in synthetic agriculturally impacted surface waters containing nitrates (20 mg L-1) and dissolved organic matter (DOM, 5.4 mgC L-1). Atrazine and S-metolachlor were quickly photodegraded by both direct and indirect processes (half-lives <5 and <7 days, respectively). DOM slowed down photodegradation while nitrates increased degradation rates. The analysis of transformation products showed that oxidation mediated by hydroxyl radicals (HO˙) predominated during indirect photodegradation. UV light (254 nm) led to significant C and N isotope fractionation, yielding isotopic fractionation values εC = 2.7 ± 0.3 and 0.8 ± 0.1‰, and εN = 2.4 ± 0.3 and -2.6 ± 0.7‰ for atrazine and S-metolachlor, respectively. In contrast, photodegradation under simulated sunlight led to negligible C and slight N isotope fractionation, emphasizing the effect of the radiation wavelengths on the isotope fractionation induced by direct photodegradation. Altogether, these results highlight the importance of using simulated sunlight to obtain environmentally-relevant isotopic fractionation values and to distinguish photodegradation and other dissipation pathways in surface waters.