Degradation Of Diuron Research Articles

Degradation of diuron by heterogeneous electro-Fenton using modified magnetic activated carbon as the catalyst.

In this work, polytetrafluoroethylene coating was firstly conducted to make stable and effective magnetic-activated carbon as a heterogeneous electro-Fenton catalyst for diuron oxidation. The catalysts were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In addition, the effects of operating parameters such as catalyst dosage, current intensity, substrate concentration and pH on the degradation of diuron were investigated. The removal efficiency of diuron was more than 95% within 120 min oxidation under the conditions of I = 100 mA, pH = 6.7 ± 0.2, catalyst loading 3 g L−1 and diuron concentration 10 mg L−1. Moreover, the catalyst durability test demonstrated that the modification of 5% PTFE on the catalyst indeed has a significant beneficial effect on the useful life of the catalyst. We compared the performance of catalysts with or without PTFE modification in consecutive experiments; the modified catalysts exhibited remarkable advantages in that the diuron removal efficiency was stable with relatively low iron leaching (<0.1 mg L−1) during ten consecutive degradation experiments, which proved the durability and reusability of the modified catalyst. This work demonstrates that such a heterogeneous EF using stable magnetic activated carbon catalyst with PTFE modification is promising for organic wastewater treatment in initial neutral pH conditions; at the same time, these good properties of the modified catalyst increase the possibility of practical application.

Use of Multivariable Analysis (ANOVA) to Compare Irradiation Sources on Diuron Destruction by Photocatalysis Using TiO2-P25 Impregnated with Sm3+, Eu3+ and Gd3+

Ions of Sm3+, Eu3+ and Gd3+ were deposited onto the surface of TiO2-P25 using an impregnation method, and the catalysts were calcined to 500°C in order to provide thermal stability to the crystalline phases. A sample of pure P25 was processed under the same synthesis conditions. The materials were characterized by physisorption of N2, X-ray diffraction and Scanning Electron Microscope and Spectroscopy UV-Vis with diffuse reflectance. It was observed by SEM that P25 had an amorphous surface forming irregular aggregates and deformations in which the studied lanthanide ions were inserted. Due to heat treatment, the P25 suffered modifications that showed a higher photocatalytic activity in the visible region, by the presence of oxygen vacancies generated by the removal of impurities (C and Cl). XRD analyses determined the distribution and crystal size of the crystalline phases presented in the P25 (anatase and rutile). Lanthanide ions possibly demonstrated an effect of superficial coalescing in the rutile phase of the P25. A completely randomized experimental design was used to determine the catalytic evaluation, and sunlight was statistically shown to be the best condition for the degradation and mineralization of diuron. Comparing treatments indicated a better option: using the catalyst with 0.3 wt% Gd under sunlight.

Visible light-assisted photocatalytic mineralization of diuron pesticide using novel type II CuS/Bi2W2O9 heterojunctions with a hierarchical microspherical structure

A hierarchical CuS/Bi2W2O9 heterojunction photocatalyst exhibits excellent photocatalytic activity for the degradation of diuron achieving 95% mineralization within 3 h of irradiation.

Diuron degradation by bacteria from soil of sugarcane crops

The isolation of microorganisms from soil impacted by xenobiotic chemicals and exposing them in the laboratory to the contaminant can provide important information about their response to the contaminants. The purpose of this study was to isolate bacteria from soil with historical application of herbicides and to evaluate their potential to degrade diuron. The isolation media contained either glucose or diuron as carbon source. A total of 400 bacteria were isolated, with 68% being Gram-positive and 32% Gram-negative. Most isolates showed potential to degrade between 10 and 30% diuron after five days of cultivation; however Stenotrophomonas acidophila TD4.7 and Bacillus cereus TD4.31 were able to degrade 87% and 68%, respectively. The degradation of diuron resulted in the formation of the metabolites DCPMU, DCPU, DCA, 3,4-CAC, 4-CA, 4-CAC and aniline. Based on these results it was proposed that Pseudomonas aeruginosa TD2.3, Stenotrophomonas acidaminiphila TD4.7, B. cereus TD4.31 and Alcaligenes faecalis TG 4.48, act on 3,4-DCA and 4-CA by alkylation and dealkylation while Micrococcus luteus and Achromobacter sp follow dehalogenation directly to aniline. Growth on aniline as sole carbon source demonstrates the capacity of strains to open the aromatic ring. In conclusion, the results show that the role of microorganisms in the degradation of xenobiotics in the environment depends on their own metabolism and also on their synergistic interactions.

Biodegradation of diuron by an endophytic fungus Neurospora intermedia DP8-1 isolated from sugarcane and its potential for remediating diuron-contaminated soils.

A diuron-degrading endophyte DP8-1 was isolated from sugarcane root grown in diuron-treated soil in the present study. The endophyte was identified as Neurospora intermedia based on the morphological characteristics and sequence analysis. The fermentation parameters including temperature, pH, inoculation size, carbon source, and initial diuron concentration were also investigated for the optimization of degradation efficiency. The results indicated that strain DP8-1 was capable of degrading up to 99% diuron within 3 days under the optimal degrading condition. The study of degradation spectrum indicated that strain DP8-1 could also degrade and utilize fenuron, monuron, metobromuron, isoproturon, chlorbromuron, linuron, and chlortoluron as substrate for strain growth. On basis of liquid chromatography-mass spectrometry analysis for the products of the degradation of diuron, strain DP8-1 metabolized diuron to produce N-(3,4-dichlorophenyl)-urea and N-(3,4-dichlorophenyl)-N-methylurea through sequential N-dealkylations. In a soil bioaugmentation experiment, the inoculation of strain DP8-1 into diuron-treated soil effectively enhanced the disappearance rate of diuron.

Combined experimental–theoretical investigation on the interactions of Diuron with a urea–formaldehyde matrix: implications for its use as an “intelligent pesticide”

The production of controlled release systems for Diuron aims to reduce some disadvantages of its conventional application and to diminish the associated environmental pollution. In this work, a matrix of urea–formaldehyde containing micro-encapsulated Diuron (Diuron–UF) is proposed to that purpose. The results of the morphology and distribution of particles sizes are expected to promote permeability allowing a water flux and the release of the pesticide. The possible interactions between the UF matrix and Diuron were investigated using experimental and theoretical techniques. The obtained results strongly suggest that the Diuron–UF interactions are weak enough to assure easy release. The shifts in the IR bands are modest, which is in line with the proposal that the interactions arise from H bonding and do not involve the formation of chemical bonds. The in vitro assays showed that the investigated material releases small amounts of the active component for extended periods of time. This behavior is expected to allow a large assimilation of the pesticide by plants, at the same time that it would prevent—or at least reduce—the environmental pollution caused by the Diuron degradation products. The gathered data combined indicate that Diuron–UF materials can be used as “intelligent pesticides”.

Direct and indirect photolysis of seven micropollutants in secondary effluent from a wastewater lagoon

The photodegradation of seven micropollutants commonly found in municipal wastewater, namely caffeine, carbamazepine, diuron, simazine, sulfamethoxazole, triclosan and 2,4-D, was investigated in pure water and secondary effluent to understand the direct and indirect photolysis of these compounds under natural sunlight irradiation. Sulfamethoxazole and triclosan were readily photodegraded with half-lives of 5.8 and 1.8 h, respectively, whilst the others were relatively resistant towards sunlight irradiation. Enhanced degradation was observed in secondary effluent compared with in the pure water matrix for all compounds, except for triclosan. It was confirmed that hydroxyl radicals played an important role in the photodegradation of the micropollutants while singlet oxygen may also play a role. The contribution of hydroxyl radical to the overall degradation of the five compounds that were resistant to direct sunlight accounted for 32%–70%. The impact of humic acid and nitrate, two known photosensitisers and wastewater components, on the photodegradation of the seven micropollutants in pure water was investigated under simulated solar radiation. The presence of nitrate promoted the photochemical loss of all seven micropollutants, however, humic acid caused promotion or inhibition, depending on the characteristics of the micropollutant. Humic acid enhanced the photolytic degradation of caffeine, sulfamethoxazole and diuron, while it hindered the photodegradation of the other four compounds by absorbing the available irradiation energy and/or reforming the parent compound. Furthermore, it was shown that there was only a small increase (up to 15%) in photodegradation of the compounds at 25 °C compared with that at 10 °C in the simulated system.

One-pot synthesis of lightly doped Zn1-x Cu x O and Au-Zn1-x Cu x O with solar light photocatalytic activity in liquid phase.

We report on the facile and low-temperature one-pot chemical synthesis of lightly doped Zn1-x Cu x O and hybrid Au-Zn1-x Cu x O photocatalysts with low Cu molar content (0<x<0.7%) using 1,3-propanediol polyol simultaneously as solvent, reducing and a stabilizing agent, without any final thermal treatment. The photocatalysts have been characterized by X-ray diffraction, N2 adsorption study, UV-vis diffuse reflectance spectroscopy, inductively coupled plasma optical emission spectroscopy, and transmission electron microscopy. The lightly doped hybrid Au-Zn1-x Cu x O photocatalysts consisted in faceted quasi-spherical large-size Au nanoparticle cores surrounded by closely packed small-size Zn1-x Cu x O nanoparticles. Taking the photocatalytic degradation of Diuron under solar light as liquid-phase test reaction, the lightly doped Au-Zn1-x Cu x O hybrid photocatalysts with optimized x=0.09% Cu content showed strongly enhanced photocatalytic activity when compared to the bare ZnO counterpart. The observed 16-fold higher degradation rate constant resulted jointly from the light doping of ZnO with Cu to form Zn1-x Cu x O photocatalyst and further from the addition of gold nanoparticles allowing interfacial oxide-to-metal electron transfer within the hybrid Au-Zn1-x Cu x O photocatalyst.

Development of photocatalytic titanium dioxide membranes for degradation of recalcitrant compounds

BACKGROUND Immobilization of TiO2 photoactive nanoparticles on a nanofiltration membrane without loss of permselectivity properties is currently a challenge. In this study, immobilization of TiO2 nanoparticles on a ceramic commercial membrane surface by direct current reactive magnetron sputtering was addressed. The best membrane was compared with an unmodified membrane and a membrane modified by a generic chemical–physical method in terms of membrane permselectivity and photocatalytic properties. RESULTS Magnetron sputtering was able to achieve similar photocatalytic activity to the chemical–physical method, where Evonik P25 TiO2 nanoparticles were used, while maintaining membrane rejection and permeability. The layer formed by magnetron sputtering exhibits uniformly distributed nanostructured columns, aligned perpendicularly to the membrane surface. Furthermore, the membrane hydrophilicity increase achieved is promising for fouling control. A shorter sputtering time and distance between the titanium target and the membrane were preferable to effectively degrade the pesticides diuron and chlorfenvinphos. Under optimum sputtering conditions, 95% and 78% increases were attained for the degradation of diuron and chlorfenvinphos, respectively, compared with the unmodified membrane. CONCLUSION The photocatalytic membranes developed are potential candidates for the simultaneous retention and photocatalytic degradation of recalcitrant micropollutants. However, if the purpose is to retain low molecular weight molecules, retentive properties should be improved. © 2016 Society of Chemical Industry

Bioremediation of diuron contaminated soils by a novel degrading microbial consortium

Diuron is a biologically active pollutant present in soil, water and sediments. It is persistent in soil, water and groundwater and slightly toxic to mammals and birds as well as moderately toxic to aquatic invertebrates. Its principal product of biodegradation, 3,4-dichloroaniline, exhibits a higher toxicity than diuron and is also persistent in the environment. On this basis, the objective of the study was to determine the potential capacity of a proposed novel diuron-degrading microbial consortium (DMC) for achieving not only diuron degradation, but its mineralisation both in solution as well as in soils with different properties. The consortium was tested in a soil solution where diuron was the only carbon source, and more than 98.8% of the diuron initially added was mineralised after only a few days. The consortium was composed of three diuron-degrading strains, Arthrobacter sulfonivorans, Variovorax soli and Advenella sp. JRO, the latter had been isolated in our laboratory from a highly contaminated industrial site. This work shows for the first time the potential capacity of a member of the genus Advenella to remediate pesticide-contaminated soils. However, neither of the three strains separately achieved mineralisation (ring-14C) of diuron in a mineral medium (MSM) with a trace nutrient solution (NS); combined in pairs, they mineralised 40% of diuron in solution, but the most relevant result was obtained in the presence of the three-member consortium, where complete diuron mineralisation was achieved after only a few days. In the presence of the investigated soils in suspension, the capacity of the consortium to mineralise diuron was evaluated, achieving mineralisation of a wide range of herbicides from 22.9 to 69.0%.

Effect of Nitrate and Sulfate Contamination on Degradation of Diuron via Electrochemical Advanced Oxidation in a Microreactor

The degradation of diuron, which is a toxic herbicide that causes a serious environmental problem in many countries, was performed using electrochemical advanced oxidation process (EAOP) in a microreactor. The influence of nitrate and sulfate contamination on the degradation was investigated. The experimental results clearly indicate that both nitrate and sulfate ions retard diuron degradation. Under the applied current of 1 mA, about 91% of diuron in deionized water is degraded within 100 s of residence time, while the degradation achieved is 79% and 76% when nitrate and sulfate ions are presented in the solution at concentration of 50 mM, respectively. Both ions behave as a scavenger for the reactive hydroxyl radical, although other mechanisms might also involve causing this retarding effect. Nitrate ion participates in diuron degradation causing new reaction pathways, while sulfate does not interfere with the diuron degradation pathway. The presence of ion in the solution also shifts the degradation route from one route to another.

Effect of W doping level on TiO2 on the photocatalytic degradation of Diuron.

In the present study, three compositions of W-doped titania nano-photocatalyst are synthesized via the sol-gel method. The powders obtained were characterized by X-ray diffraction, Raman spectroscopy and UV-visible diffuse reflectance spectroscopy. The photocatalytic performances of the different photocatalysts are tested with respect to the degradation of Diuron in water solutions under simulated solar light and visible light irradiation. The W0.03Ti0.97O2 catalyst exhibits better photoactivity than the pure TiO2 even under simulated solar light and visible light. This improvement in activity was attributed to photoelectron/hole separation efficiency.

Degradation of Diuron by Electrochemically Activated Persulfate

An electrochemically activated persulfate (EC/PS) system was proposed for the degradation of herbicide diuron in this study. In the EC/PS system, the ferrous ions (Fe2+) produced from iron electrode can activate persulfate to generate sulfate radical (SO4 ·-) as well as hydroxyl radical (OH•). The results showed that the degradation of diuron was significantly enhanced in the EC/PS system, compared to electrocoagulation, persulfate, and Fe2+/PS process. Both of SO4 ·- and OH· contributed to the degradation of diuron in the EC/PS system according to the radical scavenging studies. The pseudo first-order rate constants of diuron increased with increasing the applied currents and dosages of persulfate. pH affected the degradation of diuron indirectly through the speciation of iron and resulted in higher removal efficiency in acidic condition than in alkaline condition. Chloride, carbonate, and bicarbonate in real water inhibited the degradation of diuron dramatically through consuming SO4 ·- and OH· and abided by the order of CO3 2−>HCO3 −>Cl−. This study demonstrates that the EC/PS system is a novel, efficient, promising, and environmental-friendly method to treat diuron contamination.

Epigallocatechin-3-gallate-coated Fe3O4 as a novel heterogeneous catalyst of peroxymonosulfate for diuron degradation: Performance and mechanism

In this paper, epigallocatechin-3-gallate/Fe3O4, a novel heterogeneous catalyst to activate peroxymonosulfate for diuron degradation, was synthesized and its structure was well characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy. It was found that the hybrid catalyst showed a better catalytic efficiency than both Fe3O4 and epigallocatechin-3-gallate. This was resulted from the high reduction ability of epigallocatechin-3-gallate, which promoted the cycle of Fe(III)/Fe(II) on the surface of catalyst. Besides, batch experimental results showed that the degradation of diuron depended upon the dosage of catalyst and oxidant, initial pH, and co-existed humic acid. Results demonstrated that high catalyst and oxidant dosages, low initial pH and humic acid were favorable for diuron removal. Furthermore, by adding different dosages of methanol and tertiary butanol, two kinds of radicals were detected to be responsible for diuron degradation in this study and sulfate radical made the predominant contribution. At last, mineralization and degradation pathway were also evaluated in this study. Anyway, it was confirmed that the as-prepared catalyst has the potential superiority for contaminants removal from aqueous solution.

Degradation of diuron via an electrochemical advanced oxidation process in a microscale-based reactor

The degradation of diuron, a toxic herbicide that is widely used in many countries, in an aqueous solution was performed in a microscale-based reactor using an electrochemical advanced oxidation process (EAOP). A graphite sheet and a stainless steel plate were used as an anode and a cathode, respectively. The effects of pH, conductivity of the solution, applied current, and height of the microchannel on the degradation of diuron were investigated. Approximately 90% degradation of diuron could be achieved within 100s of residence time in the reactor that was applied with a direct current of 1mA. The experimental results clearly suggests that the degradation occurs mainly by the interaction between diuron and the hydroxyl radical generated via dissociation of water at the anode, although direct reduction of diuron by supplied electrons was also observed. The degradation generates many reaction intermediates. However, a simple reaction model employing first-order kinetics could represent the degradation well. Most of the steps in the degradation pathway proceed at approximately the same rate. This rate is much higher than the degradation rate achieved by other conventional advanced oxidation processes.

Ozonation, photocatalysis and photocatalytic ozonation of diuron. Intermediates identification

Aqueous 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) has been oxidized by ozonation, photocatalysis and photocatalytic ozonation. Diuron degradation takes place via radical pathway through hydroxyl radicals in those systems involving ozone. Diuron elimination in photocatalytic ozonation is not enhanced if compared to single ozonation; however, TOC removal was significantly improved. Specifically, 80% TOC removal in 2h was reached in photocatalytic ozonation while single ozonation just led to 25% TOC reduction. Photocatalysis required 9h to reach 25% TOC reduction. Ten transformation by-products generated during the application of the three technologies were tentatively identified by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF–MS/MS). Single ozonation and photocatalytic ozonation led to the formation and complete elimination of all by-products. Low weight carboxylic acids evolution suggests that high TOC removal in photocatalytic ozonation is linked to its capacity to oxidize small oxygenated compounds and release of inorganic chloride and nitrate. Toxicity evolution to Vibrio fischeri in photocatalytic ozonation displayed an increase in inhibition at the initial stages (>90% of inhibition), followed by a decrease of this parameter as the reaction progressed. The final treated sample shows a lower toxicity than the initial one (55% vs 20%).

Lanthanum ion doped nano TiO2encapsulated in zeozyme and impregnated in a polystyrene film as a photocatalyst for the degradation of diuron in an aquatic ecosystem

The occurrence of chlorinated herbicide diuron in water bodies is considered serious pollution and a major health hazard to flora, fauna and mankind.

Fructose as a novel photosensitizer: Characterization of reactive oxygen species and an application in degradation of diuron and chlorpyrifos.

The objective of this study was to identify reactive oxygen species (ROS) generated from the exposure of fructose solution to the 254 nm ultraviolet (UV) light and evaluate whether fructose can be used as a photosensitizer for accelerated photo-degradation of diuron and chlorpyrifos. We demonstrated that hydrogen peroxide, singlet oxygen ((1)O2) and acidic photolysis products were generated upon UV exposure of fructose. Consistent with these findings, UV induced degradation of chlorpyrifos and diuron was accelerated by the presence of 500 mM fructose. The average first order photo-degradation rate constants in the absence and presence of 500 mM fructose were 0.92 and 2.07 min(-1) respectively for diuron and 0.04 and 0.07 min(-1) for chlorpyrifos. The quantum yields (ɸ) for direct photo-degradation of diuron and chlorpyrifos were 0.003 and 0.001 respectively. In the presence of 500 mM fructose, these values increased to 0.006 and 0.002 respectively. Thus, fructose may be an effective photosensitizer.

Effect of algal organic matter (AOM) extracted from Microcystis aeruginosa on photo-degradation of Diuron

The presence of algal organic matter (AOM) and emerging organic contaminants in surface drinking water sources has received increasing attention recently. Nevertheless, interactions between these two harmful co-existing compounds in water sources have rarely been reported. This study investigated the influence of AOM, including intracellular organic matter (IOM) and extracellular organic matter (EOM), on the photo-degradation of Diuron, under UV and visible light (VL) irradiation. Kinetics analyses indicated that both the direct and indirect photolysis of Diuron followed a pseudo-first-order reaction (R2>0.98). Diuron was rapidly removed under UV irradiation accompanied by minor impacts from AOM. Under VL irradiation, the photo-excited phycocyanin in the IOM was capable of accelerating Diuron degradation, whereas the coexistence of other organic compounds in the IOM inhibited the reaction due to a screening effect, resulting in a slower overall rate of Diuron degradation. By comparison, EOM promoted the reactions when pH exceeded 5.0. The AOM-mediated generation of triplet DOM (3DOM∗) accounted for 82% and 64% of the Diuron removal in the presence of IOM and EOM, respectively. Spectral excitation–emission matrices produced by AOM in solutions demonstrated the primary mechanisms of the co-existing AOM on Diuron degradation.

Ionizing radiation induced degradation of diuron in dilute aqueous solution.

BackgroundCutting edge technologies based on Advanced Oxidation Processes (AOP) are under development for the elimination of highly persistent organic molecules (like pesticides) from water matrices. Among them, ionizing radiation treatment represents a promising technology that requires no additives and can be easily adapted to an industrial scale. In these processes several reactive species are produced, mainly powerful oxidizing radicals inducing the degradation. This paper investigates the reactions taking place in dilute aqueous solutions of a hazardous pollutant (diuron) during irradiation.ResultsIrradiation of aqueous diuron solutions resulted in effective degradation of the solute mainly due to the reactions of hydroxyl radicals formed in water radiolysis. Hydroxyl radical reacts with diuron with a second order rate constant of (5.8 ± 0.3) × 109 mol−1 dm3 s−1. The main reaction is addition to the ring forming hydroxycyclohexadienyl radical. 30 − 50% of hydroxyl radical reactions induce dechlorination. Reactions with the methyl groups or with the α-amino group have low contribution to the transformation. The presence of dissolved oxygen enhances the rate of degradation; one hydroxyl radical on average induces five-electron oxidations. The high oxidation rate is attributed to the reaction of some of the primarily formed organic radicals with dissolved O2 and the subsequent reactions of the peroxy radicals.ConclusionThe presence of dissolved oxygen is highly important to achieve efficient ionizing radiation induced degradation of diuron in dilute aqueous solution.