Photodegradation Of Imidacloprid Research Articles

Highly Efficient Photocatalytic Degradation of Imidacloprid Based on Iron Metal-Organic Frameworks of Mesoporous NH2-MIL-88b/Graphite Carbon Nitride Nanocomposites by Visible Light Driven in Aqueous Media.

Pesticides that protect crops from insects and other pests are some of the main causes of water pollution. Imidacloprid (IMC) is the most widely used insecticide in the world and should be removed from the environment. This work aims to prepare mesoporous nanocomposites to increase the photodegradation efficiency of IMC. To improve the surface properties and enhance the photocatalytic activity, mesoporous nanocomposites with different weight ratios of graphite carbon nitride (CN = 125, 250, and 500 mg) were prepared by the solvothermal method. Mesoporous NH2-MIL-88b(Fe)/graphite carbon nitride (CN = 250 mg, NH2-MCN-2) nanocomposites showed the best photocatalytic performance. To save the time and cost of the experiments, central composite design (CCD) and response surface methodology (RSM) were used and the results were obtained as the initial concentration of IMC (20 mg L-1), amount of photocatalyst (0.76 g L-1), pH = 5, and degradation time ∼46 min. The maximum photocatalytic degradation efficiency estimated by the model was obtained at 96.31%, which is very close to the actual value of 95.47%. The mesoporous NH2-MCN-2 nanocomposite showed excellent stability and suitable reusability with a maximum degradation of 84.5% after five cycles. Results obtained from kinetic studies indicated a rate constant value of 0.08 min-1, and isotherm models showed that equilibrium data are more consistent with the Langmuir model in photocatalytic degradation. Electrochemical experiments showed significant improvement in the electron transfer rate and photocatalytic activity of the mesoporous NH2-MCN-2 nanocomposite. Different trapping agents were used to investigate the effective active species in IMC photodegradation, and it was determined that the hole (h+) and OH radical (•OH) play the main role. The possible mechanism for IMC photocatalytic degradation was suggested by Mott-Schottky (M-S) electrochemical impedance.

Carbon quantum dots assisted BiFeO3@BiOBr S-scheme heterojunction enhanced peroxymonosulfate activation for the photocatalytic degradation of imidacloprid under visible light: Performance, mechanism and biotoxicity

A novel S-scheme heterojunction photocatalyst carbon quantum dots (CQDs)/BiFeO3/BiOBr (CBB) was synthesized via a facile hydrothermal method, which was highly effective in activating peroxymonosulfate (PMS) to photodegrade imidacloprid (IMD) (one of the typical neonicotinoid insecticides (NEOs)) under visible light irradiation. Based on the physicochemical and photoelectrochemical analysis, the super photocatalytic performance of the CBB photocatalyst was contributed to the enhanced separation and transfer of photogenerated electrons (e−) and holes (h+), the activation of PMS by reactive species, and the wider light absorption range induced by CQDs. Moreover, the intermediate products and possible photodegradation pathways of IMD were confirmed through high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS) detection and density functional theory (DFT) calculations. Although the photodegradation of IMD in the CBB/PMS/Vis system can be affected by the water quality parameters (i.e., acid group anions, pH, and the presence of humic acid (HA)), the synthesized CBB photocatalyst showed excellent photocatalytic performance in multiple natural water samples. This study provides a new idea to construct an effective and efficient heterojunction photocatalyst, which may have great advantages in photocatalytic degradation of NEOs and possibly other emerging contaminants in the aquatic environment.

Relationship between photolysis mechanism and photo-enhanced toxicity to Vibrio Fischeri for neonicotinoids with cyano-amidine and nitroguanidine structures

Neonicotinoids are widely used pesticides that contaminate aquatic environments. Although these chemicals can be photolyzed under sunlight radiation, it is unclear for the relationship between photolysis mechanism and toxicity change in aquatic organisms. This study aims to determine the photo-enhanced toxicity of four neonicotinoids with different main structures (acetamiprid, and thiacloprid for cyano-amidine structure, imidacloprid and imidaclothiz for nitroguanidine). To Achieve the goal, photolysis kinetics, effect of dissolved organic matter (DOM) and reactive oxygen species (ROSs) scavengers on photolysis rates, photoproducts, and photo-enhanced toxicity to Vibrio fischeri were investigated for four neonicotinoids. The results showed direct photolysis plays a key role in the photo-degradation of imidacloprid and imidaclothiz (photolysis rate constants are 7.85 × 10−3 and 6.48 × 10−3 min−1, respectively), while the photosensitization process of acetamiprid and thiacloprid was dominated by ·OH reactions and transformation (photolysis rate constants are 1.16 × 10−4 and 1.21 × 10−4 min−1, respectively). All four neonicotinoid insecticides exerted photo-enhanced toxicity to Vibrio fischeri, indicating photolytic product(s) posed greater toxicity than their parent compounds. The addition of DOM and ROS scavengers influenced photo-chemical transformation rates of parent compounds and their intermediates, leading to diverse effects on photolysis rates and photo-enhanced toxicity for the four insecticides as a result of different photo-chemical transformation processes. Based upon the detection of chemical structures of intermediates and Gaussian calculations, we observed different photo-enhanced toxicity mechanisms for the four neonicotinoid insecticides. Molecular docking was used to analyze the toxicity mechanism of parent compounds and photolytic products. A theoretical model was subsequently employed to describe the variability of toxicity response to each of the four neonicotinoids.

Visible-light responsive Au nanoparticle-decorated polypyrrole-carbon black/SnO2 ternary nanocomposite for ultrafast removal of insecticide imidacloprid and methylene blue

Highly precise, determined and mind provoking steps are must for efficacious designing of smart visible-light photocatalysts. Herein, we successfully designed an ultrafast visible-light responsive photocatalyst comprising of SnO2, polypyrrole doped carbon black (PPy-C) and gold nanoparticles (Au NPs) by a simple and reliable approach. XRD, FTIR, XPS, FESEM, TEM and UV–vis spectroscopic tools were employed for comprehensive characterization of synthesized nanostructures. XPS and XRD investigations confirmed the establishment of ternary photocatalyst among SnO2, PPy-C and Au. TEM analysis showed that synthesized SnO2 material possessed irregular nanorods of 20–100 nm length and 20 nm diameter. The PPy-C polymer combination has beads or dumbbell shape morphology intertwined with SnO2 while dispersed Au NPs can be easily seen along with PPy-C and SnO2 nanostructures. The bandgap energy (Eg) for pristine SnO2, PPy-C/SnO2 and Au@PPy-C/SnO2 nanocomposite was found to be 3.55, 3.22 and 2.85 eV, respectively. The photocatalytic performance of each newly produced photocatalyst was evaluated under visible light using imidacloprid (an insecticide derivative) and methylene blue (MB) dye as target pollutants. Among different tested photocatalysts, the newly created Au@PPy-C/SnO2 trio combination was proven to be the most proficient with 93.18 % removal of imidacloprid in just 20 min and complete destruction of MB dye only in 10 min. The degradation rate constant (k) for SnO2 and Au@PPy-C/SnO2 was found to be 0.0327 and 0.1310 min−1 respectively, revealing 4 times higher proficiency of Au@PPy-C/SnO2 than bare SnO2. The effect of variation of different parameters on imidacloprid photodegradation has also been investigated like irradiation time, reaction pH, substrate concentration and catalyst concentration. Higher photocatalytic activity has been observed at low substrate concentration under acidic condition (pH: 4) with 20 minutes as an optimal time.

Peroxymonosulfate activation by Co3O4 coatings for imidacloprid degradation in a continuous flow-cell reactor under simulated solar irradiation

In this work, a Co3O4 coating prepared by precipitation and vacuum filtration was applied to photoactivate peroxymonosulfate (PMS), for the degradation of imidacloprid (IMD) under continuous-flow conditions. The effects of PMS concentration, flow rate, and type of irradiation were evaluated. Under optimal conditions (0.2 gPMS L−1, 0.1 mL min−1, and simulated solar irradiation), 99% IMD photodegradation was achieved after 2 h of operation. The outstanding performance of the Co3O4/PMS/solar irradiation process was attributed to the synergistic activation of PMS by Co2+ and Co3+ species in the Co3O4 catalyst and the UV component of solar irradiation, in either the homogeneous phase or following the adsorption of PMS onto Co3O4. Quenching experiments revealed that sulfate and superoxide radicals, as well as singlet oxygen, were the main active species responsible for IMD oxidation. Measurements using HPLC-high resolution mass spectrometry enabled the identification of eight intermediate products, allowing the proposal of a degradation pathway. The combination of solar light, Co3O4, and PMS is a simple and low-cost approach with the potential to treat effluents containing harmful pollutants.

Prominent dual Z-scheme mechanism on phase junction WO3/CdS for enhanced visible-light-responsive photocatalytic performance on imidacloprid degradation

• The dual Z-scheme photocatalysts with phase junction WO 3 and CdS were fabricated. • The 75CW has the best photocatalytic rate of imidacloprid degradation. • The Fukui indexes were exploited to predict reactive sites. • The reliable degradation pathways of imidacloprid were proposed. The construction of dual Z-scheme photocatalysts is an effective way to promote the separation and migration of electrons-holes as well as retain their high redox abilities. Herein, a distinctive dual Z-scheme photocatalyst based on phase junction WO 3 and CdS (CW) was successfully fabricated via hydrothermal method and in-situ precipitation process. The as-prepared materials showed the advantages of both phase junction and dual Z-scheme mechanism (promoted utilization of carriers and improved redox potential). As a result, the k app value of 75CW (0.05237 min −1 ) was 29.8 times that of phase junction WO 3 (0.00176 min −1 ) and 2.9 times that of CdS (0.01799 min −1 ) in terms of imidacloprid (IMD) degradation. Trapping experiment and electron spin resonance (ESR) proved the dual Z-scheme mechanism, the key to significantly improve photocatalytic degradation efficiency of WO 3 /CdS nanocomposites. Combined the analysis of liquid chromatography-mass spectrometry (LC-MS) with density functional theory (DFT) calculation, rational degradation pathways of IMD were put forward in detail. This work is excepted to provide new horizons for the construction of dual Z-scheme system with phase junction and the photodegradation of IMD.

Phototransformation of biochar-derived dissolved organic matter and the effects on photodegradation of imidacloprid in aqueous solution under ultraviolet light

Dissolved organic matter (DOM) strongly influences the photodegradation of organic pollutants, varying depending on the structure of DOM. With the wide application of biochar, increasing amounts of DOM is released from biochar to the environment, which has different structural characteristics compared to natural DOM. In this study, DOM was derived from maize straw (MS) and pig manure (PM) and biochars by pyrolyzing MS and PM at 300 °C and 500 °C and the optical characteristics of DOM before and after phototransformation were explored via ultraviolet–visible spectroscopy and excitation–emission matrix fluorescence. Photodegradation of an insecticide, imidacloprid (IMI) in the presence of DOM was examined. The results showed that DOM derived from biochar obtained by pyrolyzing MS and PM mainly contained two identified fluorescent components and high pyrolysis temperature (500 °C) was associated with low molecular weight, small light-screening effects and great aromaticity of the DOM. After exposure to UV light, the aromaticity and molecular weight of the DOM declined due to phototransformation. Significant enhancement was observed in IMI photodegradation in the presence of biochar-derived DOM, and the enhancement was the greatest with DOM derived from pig manure biochar pyrolyzed at 500 °C. In addition to the light shielding effect, the 1O2 generated from DOM played an important role in the phototransformation of IMI and DOM. The loss of the nitro group and oxidation at the imidazolidine ring were the main photodegradation pathways for IMI. This study expands our understanding of the fate of biochar-derived DOM and its effects on the fate of coexisting organic pollutants.

One-dimensional core-shell Zn0.1Cd0.9S/Snln4S8 heterojunction for enhanced visible light photocatalytic degradation

Efficient separation of photogenerated charge carriers is vitally significant in the photocatalytic reaction process. In this work, a novel Zn0.1Cd0.9S/Snln4S8 (ZCS/SIS) core-shell nanorods photocatalyst was prepared by a facile solvothermal method. The photocatalytic activity of the as-synthesized samples were evaluated by the degradation of Rhodamine B (RhB) and imidacloprid (IM) under visible light irradiation. Compared with the pristine ZCS and SIS, the core-shell composites displayed dramatically improved photocatalytic activity. The apparent rate constants of RhB and IM photodegradation over ZCS/SIS are 5.07 and 16.9 time higher than that of pure ZCS, respectively. In addition, the electrochemical measurements indicate that the charge carriers separation in ZCS/SIS core-shell composites is enhanced. The reason could be the formation of the core-shell ZCS/SIS heterojunction boosting the charge carriers separation and transfer. Besides, a possible photocatalytic mechanism was proposed.

Imidacloprid photo-degradation on Ag/AgBr modified TiO2: critical impacts and quantitative study on mechanism

To improve the visible-light catalytic performance of TiO2 for practical application, Ag/AgBr modified TiO2 was fabricated in ionic liquid–water medium via a facile hydrothermal reduction method. Imidacloprid (IMI) was employed as the target pollutant to evaluate the critical impacts on the catalytic activity of as-prepared Ag/AgBr/TiO2, where the factors relating to the catalyst (composition, dosage, recycle and reuse) and solution chemistry (pH and concentration, simulated wastewater samples and floodwater of rice paddy field) were studied. The results suggested that benefitting from visible-light sensitive Ag/AgBr and high specific surface area TiO2, Ag/AgBr/TiO2 exhibits superior visible-light photocatalytic activity and stability to Ag/AgBr and TiO2. The quenching tests with various scavengers indicate that ·O2− and h+, and ·O2− and ·OH may be the key roles in IMI photo-degradation on Ag/AgBr and on Ag/AgBr/TiO2, respectively. Thus, the photocatalytic performance of Ag/AgBr/TiO2 differs from that of Ag/AgBr. Furthermore, the contribution of such active species is clarified for quantitative mechanisms study. The photo-degradation conducted in the simulated wastewater and the floodwater of rice paddy field proves favorable anti-interference capacity of Ag/AgBr/TiO2. The tests conducted on real wastewater sample verified that Ag/AgBr/TiO2 can mineralize IMI promptly and almost completely.

Photocatalytic degradation of imidacloprid by Ag-ZnO composite.

The present study focused on exploring the potential of Ag-ZnO composites for complete mineralization of imidacloprid with the aim to sustain the pollutant free safe water supply. The composites were prepared by hydrothermal method and characterized by Scanning electron microscope (SEM), Energy dispersive X-ray crystallography (EDX), X-ray diffraction (XRD) and band gap measurements. These composites were used to study the UV irradiated degradation of imidacloprid while optimizing the process parameters such as time of UV irradiation, pH of medium, pesticide concentration and composite loading. The results of the study revealed an increase in photodegradation of imidacloprid by Ag-ZnO composites than pure ZnO. Temperature and catalyst loading had a positive effect on degradation efficiency, while an inverse relation was observed between pesticide concentration and degradation. Moreover, no harmful degradation products of imidacloprid were observed in GC-MS analyses that confirmed its complete mineralization.

Photodegradation of Imidacloprid and Fipronil in Rice–Paddy Water

Photodegradation of insecticides, imidacloprid and fipronil, in rice-paddy water under the ambient temperature was investigated. The initial concentrations were set at 58.8 and 3.1 μg/L for imidacloprid and fipronil, respectively, according to their reported initial concentrations in the rice-paddy field. The half-lives (DT(50)) of imidacloprid and fipronil were 24.2 and 36.7 h, respectively. Fipronil desulfinyl was detected as a major metabolite and fipronil sulfone was found to be a minor metabolite of fipronil in the photodegradation process. Detected mass of fipronil, fipronil desulfinyl, and fipronil sulfone at 79 h were 12.9%, 45.8%, and 5.2% of initial fipronil mass, respectively.

Photodegradation of imidacloprid.

The photolytic decomposition of the insecticide imidacloprid (1) in HPLC grade water and of imidacloprid as the formulated product Confidor insecticide in tap water was studied using HPLC methodology. The structures of several degradates have been determined in aquatic medium, and the DT(50) values of imidacloprid and Confidor have been measured. In addition, the influence of TiO(2) on the photodegradation of Confidor was studied. The photoproduct 1-(6-chloro-3-pyridinyl)methyl-2-imidazolidinone (5) has been identified as the main degradate in each of the three series of experiments by several analytical techniques. The photolytic half-lives for imidacloprid under the conditions of this study were 43 min in HPLC grade water, 126 min formulated as Confidor in tap water, and 144 min formulated as Confidor in tap water in the presence of TiO(2).