Photocatalytic degradation of herbicide bentazone in aqueous suspension of TiO2: mineralization, identification of intermediates and reaction pathways

Resonance Rayleigh scattering technique-using chitosan-capped gold nanoparticles, approaches spectrofluorimetric method for determination of Bentazone residual in water samples

In this study, a resonance Rayleigh scattering technique-based sensing method for detecting Bentazone residual in water samples has been developed. This technique was carried out using chitosan-capped gold nanoparticles with a spectrofluorimetric method. Experimental results revealed that the developed method could allow the detection of Bentazone residual as low as a concentration of 0.02 ng mL-1 within 50-sec time. Overall results confirmed the very low detection limit for measuring the Bentazone. The chitosan-capped gold nanoparticles as an excellent sensor were applied to measure and analyze Bentazone in water samples.

Synthesis, characterization, and application of α-Fe2 O3 @TiO2 @SO3 H photo-Fenton catalyst for photocatalytic degradation of biologically pre-treated wood industry wastewater

The efficiency of removing chemical oxygen demand (COD) and turbidity from wood wastewater was investigated using a sequencing batch reactor (SBR) and the photo-Fenton process. A total of 94.78% of COD reduction and 99.9% of turbidity removal were observed under optimum conditions of SBR, which consisted of an organic loading rate (OLR) of 0.453 kg COD m^-3  day^-1 , mixed liquor suspended solids (MLSS) of 4564 mg L^-1 , and cycle time of 48 h. A magnetic α-Fe₂ O₃ @TiO₂ @SO₃ H nanocatalyst was prepared as a heterogeneous Fenton reagent. The Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and elemental mapping (MAP) analyses were performed to determine the structure and morphology of synthesized photocatalyst. The response surface methodology (RSM) was used to optimize the process based on a central composite design (CCD). The maximum photocatalytic degradation of 87.54% and COD reduction of 83.35% were achieved at a dosage of 0.6 g L^-1 of catalyst, 30 mg L^-1 of H₂ O₂ , and pH of 3.5 for 45 min. The results indicated that a combination of the SBR process and α-Fe₂ O₃ @TiO₂ @SO₃ H could be used as an effective method for the treatment of wood wastewater. PRACTITIONER POINTS: A combination of the SBR and photo-Fenton process was introduced as an impressive method for wood industry wastewater treatment. The efficiencies of COD, BOD₅ , NO₃ -N, PO₄ -P, and color removal were obtained according to the standard limits in Iran. To our knowledge, this study is the first report of the use of synthesized α-Fe₂ O₃ @TiO₂ @SO₃ H photocatalyst for the wood industry wastewater treatment.

Preparation and application of α-Fe2O3@TiO2@SO3H for photocatalytic degradation and COD reduction of woodchips industry wastewater

In this study, we investigated the efficiency of photocatalytic degradation and chemical oxygen demand (COD) reduction from woodchips industry wastewater using α-Fe₂O₃@TiO₂@SO₃H. A magnetic α-Fe₂O₃@TiO₂@SO₃H was prepared as a heterogeneous photo-Fenton catalyst. The Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and elemental mapping (MAP) analyses were performed to determine the structure and morphology of synthesized photocatalysts. The response surface methodology (RSM) was used to optimize the photo-Fenton process based on a Box-Behnken design (BBD). The parameters such as catalyst dosage, H₂O₂ dosage, pH, and contact time on photocatalytic degradation and the reduction of COD were studied. The maximum photocatalytic degradation of 93.75% and COD reduction of 86.54% were achieved at a dosage of the catalyst of 1 g L^-1, H₂O₂ dosage of 40 mg L^-1, and a pH of 3.5 at 45 min. The kinetics of the photo-Fenton process was studied for the woodchips wastewater treatment under optimum conditions. The pseudo-second-order kinetic model for photocatalytic degradation and COD reduction was obtained. The results indicated that a α-Fe₂O₃@TiO₂@SO₃H could be used as an effective heterogeneous photocatalyst for the treatment of woodchips industry wastewater. Preparation and application of α-Fe₂O₃@TiO₂@SO₃H for photocatalytic degradation and COD reduction of woodchips industry wastewater.

Photocatalytic removal of bentazon by copper doped zinc oxide nanorods: Reaction pathways and toxicity studies

In this study, bentazon herbicide was degraded photocatalytically by copper doped zinc oxide nanorods fabricated by using a facile co-precipitation method. The crystal structure, morphology, surface composition, functional groups on the surface and valence state of the nanorods were investigated by XRD, SEM-EDX, FTIR, and XPS material characterization techniques. Environmental parameters including solution pH, catalyst dose, bentazon concentration, purging gases, H₂O₂ content, organic compound type and reusability affecting the rate of photocatalytic degradation of bentazon were evaluated. Under the optimal conditions, [Bentazon]₀ = 20 mg L^-1, Cu-ZnO loading = 0.5 g L^-1, H₂O₂ = 2 mM, pH = 7 and in the presence of oxygen gas, 100% of the herbicide was removed within 60 min. By raising bentazon concentration (10-50 mg L^-1), k_obs decreased to values between 0.14 and 0.006 min^-1 and the calculated electrical energy per order (E_Eo) increased from 38.16 to 727.27 (kWh m^-3), respectively. The degradation removal of the herbicide using the UV/Cu-ZnO method (98.28%) was higher than that of the UV/ZnO method (32.14%) process. Interestingly, the photocatalytic performances in the first and fifth reuse cycles during catalyst recyclability tests were found to be similar. Generally, the efficacy of the method in the decomposition of bentazon in drinking water (78.95%) and actual sewage (46.77%) declined because of the presence of other anions due to their role as a scavenger of photogenerated reactive species. Intermediate products in the photocatalytic degradation of bentazon identified by gas chromatography/mass spectrometry (GC/MS) analysis were 2-amino-N-isopropyl-benzamide, 2-amino-benzoic acid, N-isopropyl-2-nitro-benzamide, and acids such as pentenedioic acid, oxalic acid and propenoic acid. Furthermore, the main mechanism for the photocatalytic removal of bentazon was determined to be via attack by hydroxyl radicals (^•OH). The results of toxicity in the photocatalytic removal of bentazon by D. magna showed LC₅₀ and toxicity unit (TU) 48 h equal to 46.10 and 9.56 vol percent.

Enhanced fluorescent sensing probe via PbS quantum dots functionalized with gelatin for sensitive determination of toxic bentazon in water samples

Fluorescent chemical sensors to detect materials, by increasing fluorescence emission and absorption or by shutting down, because they are nondestructive, the ability to show decomposed concentrations, fast response, high accuracy have been considered and used. In this research, a chemical sensor was synthesized PbS functionalized with gelatin quantum dots for the determination of toxic bentazon (BTZN) one of the most problematic pesticides polluting in water samples, and extremely harmful to humans and animals even at low concentrations. The calibration curve was linear in the range of (0.05 to 200.0 ng mL^-1). The current response was linearly proportional to the BTZN concentration with a R²∼ 0.999. The standard deviation of less than (3%), and detection limits (3S/m) of the method (0.5 ng mL^-1, in time 50 s, 325 nm) were obtained for sensor level response PbS Quantum Dot-Gelatin nanocomposites sensor with (99%) which is below the U.S. Health Advisory level. The observed outcomes confirmed the suitability recovery and a very low detection limit for measuring the BTZN. The method fluorometric introduced to measure BTZN in water samples was used and can be used for in different intricate matrices, the chemical PbS Quantum Dot-Gelatin nanocomposites sensor made it possible as an excellent sensor with good reproducibility.

Remediation of bentazone contaminated water by Trametes versicolor: Characterization, identification of transformation products, and implementation in a trickle-bed reactor under non-sterile conditions

Bentazone, an herbicide widely applied in rice and cereal crops, is widespread in the aquatic environment. This study evaluated the capacity of Trametes versicolor to remove bentazone from water. The fungus was able to completely remove bentazone after three days at Erlenmeyer-scale incubation. Both laccase and cytochrome P450 enzymatic systems were involved in bentazone degradation. A total of 19 transformation products (TPs) were identified to be formed during the process. The reactions involved in their formation included hydroxylations, oxidations, methylations, N-nitrosation, and dimerization. A laccase mediated radical mechanism was proposed for TP formation. In light of the results obtained at the Erlenmeyer scale, a trickle-bed reactor with T. versicolor immobilized on pine wood chips was set up to evaluate its stability during bentazone removal under non-sterile conditions. After 30 days of sequencing batch operation, an average bentazone removal of 48% was obtained, with a considerable contribution of adsorption onto the lignocellulosic support material. Bacterial contamination, which is the bottleneck in the implementation of fungal bioreactors, was successfully addressed by this particular system according to its maintained performance. This research is a pioneering step forward to the implementation of fungal bioremediation on a real scale.

Au@Ag bimetallic nanoparticles deposited on palygorskite in the presence of TiO2 for enhanced photodegradation activity through synergistic effect

Herbicides are hazardous organic pollutants that contribute to the risk of environmental contamination. The aim of this work was to investigate the synergistic effect of silver (Ag) and gold (Au) bimetallic nanoparticles deposited on palygorskite (PAL) in the presence of TiO₂ for photodegradation of bentazone (BTZ) herbicide under UV light. Ag and Au@Ag nanoparticles exhibited an average size below 75 nm and surface charge values less than - 30 mV. UV-Vis spectroscopy indicates the formation of core@shell bimetallic nanoparticles. XRD results showed the interactions between the NPs and the palygorskite structure. SEM images clearly illustrate the presence of small spherical particles distributed in the clay fibers. The control of the size and distribution of the nanoparticles played an important role in the properties of the composites. The degradation of the herbicide BTZ showed that nanoparticles, clay, and only TiO₂ did not produce satisfactory results; however, when Ag-Pal and Au@Ag-Pal were in the presence of the TiO₂, the degradation was efficient. The best photodegradative system was Au@Ag-Pal+TiO₂, which was maintained after the third cycle. The bentazone photodegradation using Au@Ag-PAL+TiO₂ exhibited toxicity against Artemia salina. Therefore, Au@Ag-PAL+TiO₂ photocatalyst showed that the synergy of bimetallic nanoparticles deposited on clay for enhanced photodegradation activity of bentazone herbicide.

Green synthesis of Ag/ZnO microplates by doping Ag ions on basic zinc carbonate for fast photocatalytic degradation of dyes

The Ag/ZnO microplates, composed by various nanoparticles, were facilely synthesized by calcination of the precursor obtained by ion exchanging between zinc carbonate hydroxide [Zn₂(OH)₂CO₃] and silver nitrate (AgNO₃) in a short time. The structures of ZnO and Ag/ZnO were characterized carefully by a series of methods and so on. Especially, the results from the UV-Vis-NIR diffuse reflectance and PL spectra confirmed that the presence of metallic Ag led to the fact that the adsorption of visible light and an increase of separation of electrons and holes in the Ag/ZnO composite. The photocatalytic activities of the Ag/ZnO were 1.5 and nearly 5 times higher that of ZnO for removal of RhB and MB, respectively. We proposed a possible mechanism to explain the enhanced photocatalytic degradation over Ag/ZnO under UV light irradiation. Finally, this work could provide a simple example for the synthesis of metal-semiconductor composite as well as their applications.

Layered platforms of Ti4O7 as flow-through anodes for intensifying the electro-oxidation of bentazon

In this study, we prepared Ti₄O₇ porous electrodes with continuous layered structures characterized by different layer-to-layer distance (from 2 to 10 μm) but the same total void fraction (88-90%), to modulate the electrodes' permeability and the volumetric electrochemical surface area (from 90 to 840 cm² cm^-3). These platforms were evaluated as anodes in the electro-oxidation (EO) of bentazon in a three-electrode cell under galvanostatic conditions, operated both in traditional batch (TB) or batch recycle flow-through (BRFT) modes. The performance was significantly enhanced when the liquid was recirculated through the lamellar structure of the electrodes. In BRFT mode, the electrode interlayer gap was found to be a key factor to control the bentazon and total organic carbon (TOC) conversions. For the best conditions evaluated (BRFT, 10 μm-interlayered Ti₄O₇ electrodes with a volumetric surface area of 90 cm² cm^-3), the effect of the applied current (1 or 3 mA) and liquid flow rate (10, 12 or 14 mL. min^-1) was investigated. Specific energy consumption (SEC) values were estimated to reveal the performance of each of the EO treatments from an energetic point of view. The use of 10 μm-interlayered Ti₄O₇ electrodes at 1 mA in BRFT mode at a flow rate of 14 mL min^-1 showed the best results, yielding 85% bentazon removal, 57% mineralization and SEC values of 0.006 kWh.g_TOC^-1 after 6 h of treatment. This contribution highlights the use of layered Ti₄O₇ electrodes as a promising strategy for intensifying EO processes, pointing to a trade-off between the accessibility to the internal electrode structure and the volumetric electrode surface area to enhance the contact between the target molecules and the hydroxyl radicals physisorbed on the electrode surface, while minimizing simultaneously the energy requirements.

The role of direct photolysis in the photodegradation of the herbicide bentazone in natural surface waters

The photochemical fate of the herbicide bentazone was assessed by lab experiments and modeling tools. Experimental and modeling results showed that bentazone is mainly photodegraded by direct photolysis in natural water samples, even in the presence of dissolved organic matter (DOM) that can act as light-screening agent, photosensitizer and scavenger of reactive species. Even when it was dissolved in natural water samples containing different DOM amounts, the phototransformation kinetics of bentazone was unchanged compared to irradiation runs in ultrapure water. This finding suggests that the DOM and the other components of our samples did not affect the direct photolysis of bentazone by light-absorption competition, at least at the experimental optical path lengths, and did not induce significant indirect photodegradation by producing reactive transient species. Photochemical modeling in a lake-water photoreactivity scenario corroborated the observed experimental results, showing the predominant role of direct photolysis in the overall (direct + indirect) photodegradation of bentazone at different water depths and DOM contents. However, the model predicted a minor but non-negligible contribution of indirect photochemistry (i.e., reactions triggered by HO^•, CO₃^•- and ³CDOM*) to the herbicide degradation. This contribution (especially by ³CDOM*) could become crucial in deep and DOM-rich water bodies. Finally, several photoproducts formed by direct photolysis and HO^•-induced photodegradation were identified, which should not be particularly toxic for aquatic organisms and Vibrio fischeri bacteria.

Synthesis of urchin-like and yolk-shell TiO2 microspheres with enhanced photocatalytic properties

The novel urchin-like and yolk-shell titania microspheres (henceforth called UYTMs) with nanowires/microspheres hierarchical structures were successfully synthesized by a synthetic sol-gel and hydrothermal method without using any template. Uniform TiO₂ microspheres were firstly prepared by the sol-gel method, and the great monodispersed properties was delicately regulated by using the surfactant of KCl, aniline and a proper amount of water. The urchin-like yolk-shell morphology was further achieved by a NaOH-assisted hydrothermal process, and the diameter and shell thickness of the UYTMs were highly controlled by the concentration of NaOH. The detailed morphology, chemical composition and crystallinity of the UYTMs were systematically characterized by several techniques, and the underlying formation mechanisms was attentively discussed as well. The photodegradation of methylthionine chloride experiments indicated the UYTMs showed much better photocatalytic activity than that of commercial P25. This is mainly because the UYTMs exhibited much more reactive sites, higher adsorption ability and tuned optical absorption behaviour owing to their large specific surface area, hierarchical structures and the special hollow yolk-shell structure.

Recent Development on the Electrochemical Detection of Selected Pesticides: A Focused Review

Pesticides are heavily used in agriculture to protect crops from diseases, insects, and weeds. However, only a fraction of the used pesticides reaches the target and the rest slips through the soil, causing the contamination of ground- and surface water resources. Given the emerging interest in the on-site detection of analytes that can replace traditional chromatographic techniques, alternative methods for pesticide measuring have recently encountered remarkable attention. This review gives a focused overview of the literature related to the electrochemical detection of selected pesticides. Here, we focus on the electrochemical detection of three important pesticides; glyphosate, lindane and bentazone using a variety of electrochemical detection techniques, electrode materials, electrolyte media, and sample matrix. The review summarizes the different electrochemical studies and provides an overview of the analytical performances reported such as; the limits of detection and linearity range. This article highlights the advancements in pesticide detection of the selected pesticides using electrochemical methods and point towards the challenges and needed efforts to achieve electrochemical detection suitable for on-site applications.

Hydrolysis and photolysis of bentazone in aqueous abiotic solutions and identification of its degradation products using quadrupole time-of-flight mass spectrometry

Hydrolysis and photolysis of bentazone in abiotic aqueous solutions were examined under laboratory conditions. Hydrolysis was studied in different buffer solutions (pH 4.0 ± 0.1, 7.0 ± 0.1, and 9.0 ± 0.1), at different temperatures (15 °C ± 2 °C, 25 °C ± 2 °C, 35 °C ± 2 °C, and 45 °C ± 2 °C), and at different Fe³⁺ concentrations (1, 5, and 10 mg/L). Photolysis was assessed in different buffer solutions and at different solvent (methanol and ethyl acetate) concentrations (10%, 20%, and 30%) or Fe³⁺ (1, 5, and 10 mg/L) concentrations and under mercury or xenon light irradiation. Hydrolysis half-lives ranged 46-99 days at three different conditions. Photolysis half-lives ranged 2.3-7.5 h in three different conditions under mercury and xenon irradiation. Hydrolysis and photolysis of bentazone were accelerated by both alkaline conditions and elevated temperatures, and solvents and Fe³⁺ strongly enhanced bentazone degradation. Photodecomposition was much faster under a mercury lamp than under a xenon lamp. N-methyl bentazone and 6-OH bentazone/8-OH bentazone were identified as degradation products using UPLC-Q-TOF-MS. The data generated from this study could be useful for risk assessment of pesticides in the environment.

Influence of electrolysis conditions on the treatment of herbicide bentazon using artificial UVA radiation and sunlight. Identification of oxidation products

The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H₂O₂ (AO-H₂O₂), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO₂-based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO₂-based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe²⁺ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm^-2 yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids.

Preparation and application of α-Fe2O3@MIL-101(Cr)@TiO2 based on metal–organic framework for photocatalytic degradation of paraquat

In this study, a new magnetic α-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst was successfully synthesized. The material synthesized had been fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, transmission electron microscopy, and Brunauer–Emmett–Teller isotherm methods. The X-ray diffraction analysis corroborates that nanoparticles are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO2, respectively. In addition, the photocatalytic degradation of the herbicide paraquat in the presence of α-Fe2O3@MIL-101(Cr)@TiO2 under ultraviolet (UV) irradiation was studied. The effect of experimental parameters such as the initial concentration of catalyst, the pH, and the initial paraquat was investigated. The optimal conditions were achieved for concentration of catalyst 0.2 g L−1, pH 7, and concentration of paraquat 20 mg L−1. The photocatalytic degradation efficiency was 88.39% after 15 min with α-Fe2O3@MIL-101(Cr)@TiO2 under UV irradiation. The pseudo-second-order kinetic model for photocatalytic degradation of paraquat was obtained. The catalysts could be recovered and reused without any loss of efficiency for five times in the consequent reactions. To the best of our knowledge, this is the first report on the photocatalytic degradation of paraquat using new α-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst under UV irradiation condition.

Basagran® induces developmental malformations and changes the bacterial community of zebrafish embryos

This study aimed to assess the effects of Basagran^® on zebrafish (Danio rerio) embryos. The embryos were exposed to Basagran^® at concentrations ranging from 120.0 to 480.6 mg/L, and the effects on embryo development (up to 96 h) and bacterial communities of 96 h-larvae were assessed. The embryo development response was time-dependent and concentration-dependent (106.35 < EC₅₀ < 421.58 mg/L). The sensitivity of embryo-related endpoints decreased as follows: blood clotting in the head and/or around the yolk sac > delay or anomaly in yolk sac absorption > change in swimming equilibrium > development of pericardial and/or yolk sac oedema > scoliosis. A PCR-DGGE analysis was used to evaluate changes in the structure, richness, evenness and diversity of bacterial communities after herbicide exposure. A herbicide-induced structural adjustment of bacterial community was observed. In this study, it was successfully demonstrated that Basagran^® affected zebrafish embryos and associated bacterial communities, showing time-dependent and concentration-dependent embryos' developmental response and structural changes in bacterial community. Thus, this work provides for the first time a complementary approach, which is useful to derive robust toxicity thresholds considering the embryo-microbiota system as a whole. The aquatic hazard assessment will be strengthened by combining current ecotoxicological tests with molecular microbiology tools.

Titanium as a Beneficial Element for Crop Production

Titanium (Ti) is considered a beneficial element for plant growth. Ti applied via roots or leaves at low concentrations has been documented to improve crop performance through stimulating the activity of certain enzymes, enhancing chlorophyll content and photosynthesis, promoting nutrient uptake, strengthening stress tolerance, and improving crop yield and quality. Commercial fertilizers containing Ti, such as Tytanit and Mg-Titanit, have been used as biostimulants for improving crop production; however, mechanisms underlying the beneficial effects still remain unclear. In this article, we propose that the beneficial roles Ti plays in plants lie in its interaction with other nutrient elements primarily iron (Fe). Fe and Ti have synergistic and antagonistic relationships. When plants experience Fe deficiency, Ti helps induce the expression of genes related to Fe acquisition, thereby enhancing Fe uptake and utilization and subsequently improving plant growth. Plants may have proteins that either specifically or nonspecifically bind with Ti. When Ti concentration is high in plants, Ti competes with Fe for ligands or proteins. The competition could be severe, resulting in Ti phytotoxicity. As a result, the beneficial effects of Ti become more pronounced during the time when plants experience low or deficient Fe supply.

Adsorption of bentazone herbicide onto mesoporous silica: application to environmental water purification

Within the last few years, the presence of bentazone herbicide has been observed in many water resources. For the first time, removal of bentazone using mesoporous silica was investigated revealing reversible adsorption. The adsorption isotherm was well described using the Freundlich model. The affinity towards bentazone is strongly affected by pH in the range of 2-7, decreasing with the increase of the pH, becoming negligible at the neutrality. Regeneration of the adsorbent was possible, and a recovery as high as 70 % was obtained using CH3OH-NaOH solution. Furthermore, appreciable recovery (47 %) was also obtained using water. Applications on the purification of lake water and wastewaters, both characterized by a significant organic carbon load, spiked with 2 mg L(-1) bentazone were tested, observing removal yields in the range of 61-73 %. Taking advantage of the fast adsorption kinetics observed, an in-flow purification treatment was set-up, with quantitative removal of bentazone from polluted water.

Photocatalytic Degradation of Trifluralin, Clodinafop-Propargyl, and 1,2-Dichloro-4-Nitrobenzene As Determined by Gas Chromatography Coupled with Mass Spectrometry

Phototransformation is considered one of the most key factors affecting the fate of pesticides. Therefore, our study focused on photocatalytic degradation of three selected pesticide derivatives: trifluralin (1), clodinafop-propargyl (2), and 1,2-dichloro-4-nitrobenzene (3). The degradation was carried out in acetonitrile/water medium in the presence of titanium dioxide (TiO2) under continuous purging of atmospheric air. The course of degradation was followed by thin-layer chromatography and gas chromatography-mass spectrometry techniques. Electron ionization mass spectrometry was used to identify the degradation species. GC-MS analysis indicates the formation of several intermediate products which have been characterized on the basis of molecular ion, mass fragmentation pattern, and comparison with NIST library. The photocatalytic degradation of pesticides of different chemical structures manifested distinctly different degradation mechanism. The major routes for the degradation of pesticides were found to be (a) dealkylation, dehalogenation, and decarboxylation, (b) hydroxylation, (c) oxidation of side chain, if present, (d) isomerization and cyclization, (e) cleavage of alkoxy bond, and (f) reduction of triple bond to double bond and nitro group to amino.