Green synthesis of alumina/graphene oxide nanocomposites for photodegradation of imidacloprid

BACKGROUNDThis research deals with the photocatalytic degradation of the neonicotinoid insecticide imidacloprid. The reaction was carried out using a flat‐plate photoreactor in recirculated batch mode over an immobilized layer of a nitrogen‐doped TiO2 photocatalyst. The characterization of the prepared photocatalyst was performed using various instrumental techniques. The irradiation sources used were UV 365 nm high‐power light‐emitting diodes (LEDs) with various powers (20 and 30 W) and irradiation intensities. The radiation intensities were changed by adjusting the voltage supplied to the UVA‐LED radiation source. Design of experiments was used to evaluate the influence of three selected variables, namely initial concentration of imidacloprid solution, pH and UVA‐LED irradiance, on the photodegradation efficiency.RESULTSDoping the photocatalyst with nitrogen using urea as the nitrogen source leads to a decrease in the bandgap, Eg, compared to the characteristic values obtained for a commercial unmodified TiO2‐P25 photocatalyst (2.92 ± 0.021 versus 3.38 ± 0.015 eV). Analysis of the results using the Design‐Expert software package showed that irradiance was the most significant factor in the process studied.CONCLUSIONSTreatment of TiO2 with urea is more efficient method of TiO2 modification than nitrogen plasma pretreatment which resulted in a smaller decrease in Eg. The statistical parameters of the model equation obtained from analysis of variance confirmed the satisfactory fit of the proposed reduced cubic model to the experimental data. The results of kinetic analysis showed that the photocatalytic degradation of imidacloprid can be described by pseudo‐first‐order kinetics. © 2022 Society of Chemical Industry (SCI).

The composite of TiO2 and zeolite H-ZSM-5 has great photocatalytic ability for organic contaminants over a very large specific surface area and highlighted adsorption capacity. To describe abiotic degradation of imidacloprid, the photoinduced degradation of the pesticide imidacloprid in aqueous solutions, in the presence of TiO2 supported on H-ZSM-5 as photocatalyst, was performed. The study focused on the comparison of the imidacloprid degradation between photolysis and photocatalysis. The experimental results showed that the degradation of imidacloprid was more rapid in the condition of photocatalytic than that of photolysis or TiO2-only. The identification of possible intermediate products during the degradation was investigated by the high-performance liquid chromatography coupled with electrospray time-of-flight mass spectrometry (HPLC/TOF-MS). The main photocatalytic products were identified as chloronictinic acid, 1-[(6-chloro-3-pyridinyl) methyl]-2-imidazolidinone and 1-[(6-chloro-3-pyridinyl) methyl]-N-nitroso-2-imidazolidimine.

Photocatalytic degradation of imidacloprid by composite catalysts H3PW12O40/La-TiO2

Hydrothermal synthesis of (m-t)BiVO4/g-C3N4 heterojunction for enhancement in photocatalytic degradation of imidacloprid

Self-assembly of tungstophosphoric acid/acidified carbon nitride hybrids with enhanced visible-light-driven photocatalytic activity for the degradation of imidacloprid and acetamiprid

In the current arena, new-generation functional nanomaterials are the key players for smart solutions and applications including environmental decontamination of pollutants. Among the plethora of new-generation nanomaterials, graphene-based nanomaterials and nanocomposites are in the driving seat surpassing their counterparts due to their unique physicochemical characteristics and superior surface chemistry. The purpose of the present research was to synthesize and characterize magnetite iron oxide/reduced graphene oxide nanocomposites (FeNPs/rGO) via a green approach and test its application in the degradation of methylene blue. The modified Hummer's protocol was adopted to synthesize graphene oxide (GO) through a chemical exfoliation approach using a graphitic route. Leaf extract of Azadirachta indica was used as a green reducing agent to reduce GO into reduced graphene oxide (rGO). Then, using the green deposition approach and Azadirachta indica leaf extract, a nanocomposite comprising magnetite iron oxides and reduced graphene oxide i.e., FeNPs/rGO was synthesized. During the synthesis of functionalized FeNPs/rGO, Azadirachta indica leaf extract acted as a reducing, capping, and stabilizing agent. The final synthesized materials were characterized and analyzed using an array of techniques such as scanning electron microscopy (SEM)-energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis, and UV–visible spectrophotometry. The UV–visible spectrum was used to evaluate the optical characteristics and band gap. Using the FT-IR spectrum, functional groupings were identified in the synthesized graphene-based nanomaterials and nanocomposites. The morphology and elemental analysis of nanomaterials and nanocomposites synthesized via the green deposition process were investigated using SEM–EDX. The GO, rGO, FeNPs, and FeNPs/rGO showed maximum absorption at 232, 265, 395, and 405 nm, respectively. FTIR spectrum showed different functional groups (OH, COOH, C=O), C–O–C) modifying material surfaces. Based on Debye Sherrer's equation, the mean calculated particle size of all synthesized materials was < 100 nm (GO = 60–80, rGO = 90–95, FeNPs = 70–90, Fe/GO = 40–60, and Fe/rGO = 80–85 nm). Graphene-based nanomaterials displayed rough surfaces with clustered and spherical shapes and EDX analysis confirmed the presence of both iron and oxygen in all the nanocomposites. The final nanocomposites produced via the synthetic process degraded approximately 74% of methylene blue. Based on the results, it is plausible to conclude that synthesized FeNPs/rGO nanocomposites can also be used as a potential photocatalyst degrader for other different dye pollutants due to their lower band gap.

The presence of imidacloprid in surface waters has raised major environmental concern worldwide. Herein, for degradation and mineralization of imidacloprid, hybrid nano-catalysts g-C3N4/ZnO (< 20 nm) with different compositions were synthesized and characterized. Under UV-C light intensity of 15 W/m2 and at pH 7, degradation was observed to be highest (95.6%) for g-C3N4/ZnO (20:80) in comparison to bare ZnO (80.6%) and g-C3N4 (84.1%) nano-catalysts in just 35 min. The remarkable increase in photocatalytic activity was due to improved surface area (42.87 m2g−1), lower bandgap (2.76 eV) and lower photoluminescence intensity which resulted in lowering the recombination rate of electron–hole charge carriers. Further, higher zeta potential (+28 mV) at pH 7 might have increased intimacy in positively charged catalyst and high electron rich aromatic ring of imidacloprid which enhanced the degradation. The study was extended to analyze the reaction intermediates using LC–MS. The degradation mechanism revealed the formation of by-products such as ethylenediamine, nitroamine, acrolein, CO2 and H2O. Overall, g-C3N4/ZnO (20:80) was found to be a promising catalyst for the degradation of imidacloprid at neutral pH.

This study focused on the photocatalytic degradation of imidacloprid (IM) in water as the model pesticides. The effective division of photogenerated charge carriers is important in the photocatalytic reactions. So, a new PANI/WO3-CdS photocatalyst was synthesized by a simple method. The prepared PANI/WO3-CdS nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy compatible with energy dispersive spectroscopy (FESEM-EDS), and X-ray diffraction (XRD). Degradation of IM pesticide under visible light irradiation was carried out to investigate the photocatalytic efficiency of the prepared nanocomposite. The effect of operational parameters on the degradation performance of pesticides was studied by response surface methodology (RSM). The optimum conditions for photocatalytic degradation of IM (94.7%) were found to be 10 ppm of IM, 150 mg of PANI/WO3-CdS, and pH = 3.0. The apparent rate constant of IM photodegradation over PANI/WO3-CdS was 0.016 min-1. According to results, PANI/WO3-CdS can serve as an efficient, and recyclable photocatalyst for imidacloprid degradation in an aqueous media.

Solid catalysts consisting of polyoxometalates (POM) namely phosphotungstic acid H3PW12O40 (HPW) supported on a mesoporous sieve MCM‐41 have been prepared and characterized by FT‐IR, X‐ray diffraction, nitrogen adsorption and high resolution transmission electron microscope (HRTEM). The HPW/MCM‐41 with different HPW loadings from 10 to 60 wt% possess large specific surface area and rather uniform mesopores. Keggin structure of HPW retains on the prepared composite catalysts. The photocatalytic performance of HPW/MCM‐41 was examined by degradation of a durable pesticide imidacloprid. It is found that the prepared photocatalysts exhibit high activity under irradiation of 365 nm monochromatic light. For 50 mL of imidacloprid (10 mg/L), conversion of imidacloprid using 20 mg of HPW/MCM‐41 with 50 wt% loading level and calcined at 300°C reaches 58.0% after 5 h irradiation.

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.

Imidacloprid (IMI), a widely used neonicotinoid pesticide, has led to significant water contamination due to excessive use. As a result, there is an urgent need for effective and straightforward methods to remove IMI residues from water. Photocatalytic technology, an integral part of advanced oxidation processes, is particularly promising due to its renewability, high catalytic efficiency, fast degradation ratio, and cost-effectiveness. This review systematically examines recent progress in the photocatalytic degradation of imidacloprid in aqueous solutions using various solid catalysts. It provides a comparative analysis of key factors affecting catalytic performance, such as catalyst synthesis methods, reaction times, catalyst loading, and IMI concentrations. Among the solid catalysts studied, nano-ZnO achieved a higher degradation rate of IMI in a shorter period and with a reduced catalyst dosage, reaching approximately 95% degradation efficiency within one hour. Additionally, this review explores the types of heterojunctions formed by the catalysts and elucidates the mechanisms involved in the photocatalytic degradation of IMI. In conclusion, this review offers a comprehensive evaluation of solid catalysts for the photocatalytic removal of IMI from water, serving as an important reference for developing innovative catalysts aimed at eliminating organic pollutants from aquatic environments.

Photocatalytic degradation of imidacloprid in the flat-plate photoreactor under UVA and simulated solar irradiance conditions—The influence of operating conditions, kinetics and degradation pathway

The use of a biocompatible and thermoresponsive polymer, poly(2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO2. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability were observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g−1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8% of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications.

Research focused on the degradation of organic pollutants has seen considerable growth in recent years. The present investigations report a green chemistry route for the creation of ZnS nanoparticles (ZnS NPs) by employing the banana peel extract. X-ray diffraction analysis of the developed material established that the developed material has a cubic structure, while the FTIR spectrum of the fabricated ZnS NPs revealed the functional group present on the surface of the material exhibiting its suitability for the adsorption of the organic pollutant. SEM analysis of the material demonstrated the spherical particles with irregular morphology, and the average size of the material was estimated to be 52nm. The fabricated ZnS NPs were utilized to capture the hazardous phenol and p-nitrophenol from wastewater. The influence of various process variables including the initial concentration of the pollutant, catalyst dose, pH, and contact time was examined to optimize the maximum efficiency of the photodegradation process. The optimum degradation of the p-nitrophenol and phenol was achieved to be 71% and 80%, respectively, under the specified condition; initial p-nitrophenol concentration 20 PPM, catalyst doses 0.6 gm/L, and the pH 10.

Green synthesis has been introduced as an alternative to chemical synthesis due to the serious consequences. Metal nanoparticles synthesized through green approach have different pharmaceutical, medical and agricultural applications. The present study followed a green and simple route for the preparation of potentially bioactive gold nanoparticles (Au NPs). Au NPs were prepared via green synthesis approach using crude basic alkaloidal portion of the tuber of Delphinium chitralense. The green synthesized Au NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) fourier transform infrared (FTIR), and UV-Visible spectrophotometer. Morphological analysis shows that Au NPs have cubic geometry with different sizes. UV-Vis spectroscopic analysis confirmed the synthesis of Au NPs while XRD proved their pure crystalline phase. The Au NPs showed promising dose dependent inhibition of both AChE and BChE as compared to the crude as well as standard drug.